thomas young's lectures at the royal institution

Thomas Young's Lectures at the Royal InstitutionAuthor(s): G. N. CantorSource: Notes and Records of the Royal Society of London, Vol. 25, No. 1 (Jun., 1970), pp. 87-112Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/530866 .

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87

THOMAS YOUNG'S LECTURES AT THE ROYAL INSTITUTION

By G. N. CANTOR

Department of the History and Philosophy of Science, Indiana University

[Plates 3 and 4]

T HOMAS YOUNG, F.R.S. (1773-1829) achieved renown not only for the

original contributions which he made to physics but also, to a lesser extent, for his work in the fields of hieroglyphics, physiology and classics. Yet he was a

professional scientist for only two years (I802-I803), when he held the chair of Natural Philosophy at the Royal Institution. In this paper Young's progress during these two years will be examined, firstly from a biographical point of view and secondly with respect to the development of his scientific ideas. In both these sections the emphasis will be on the lectures in natural philosophy which he delivered before the Royal Institution in 1802 and repeated in the

following year. The second section will be mainly devoted to an analysis of the contents of the notebooks in which he kept the notes for his lectures (I).

I

Young (2), received part of his elementary education at school, but to a large extent he was self-educated. In 1792 he attended the school of anatomy set up in London by the late William Hunter and in the following year he enrolled in lectures at St Bartholomew's Hospital. It was during these early studies that he wrote his first full-length scientific paper dealing with the method ofaccommo- dation of the eye (3). He proposed that the eye's crystalline lens changes shape in order to effect accommodation and he adduced both better qualitative and

quantitative arguments in support of this hypothesis than had previously been

proposed. Little more than a year after this paper was read, Young was elected a Fellow of the Royal Society at the early age of 2I.

In the autumn of 1794 he arrived in Edinburgh where he continued his medical studies and shed some of the austerity associated with his Quaker up- bringing. He travelled in the following year to Gottingen, one of several Conti- nental universities which welcomed large numbers of English students particularly medical students from non-Anglican backgrounds (4). At Gottingen he wrote his doctoral dissertation part of which dealt with the human voice (5).



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This work led him to investigate 'the physical and mathematical theory of sound in general' (6), after he had transferred his studies to Cambridge early in 1797 in order to obtain an English degree. In 1799 he presented the results of these investigations to the Royal Society in a letter to one of its Secretaries, Dr E. W.

Gray (7). The contents of the tenth section of this paper were of particular importance in the development of his optical theory for here he first expounded the analogy between light and sound. At this stage he did little more than note the superficial elements of this analogy and promised a fuller explanation of optical phenomena on the wave theory of light. This analogy required the existence of a subtle medium, the luminiferous ether, which would 'carry' the light waves in the same way as sound waves are propagated through air.

At the end of the eighteenth century the corpuscular theory of light was dominant in England although its advocates were generally not concerned about its shortcomings. The name of Newton had become inseparable from this doctrine and his objections to the wave theory ensured that it attracted few, if any, advocates in England. Young's contribution at this time was to point out that the corpuscular theory is liable to objections because it failed to explain both partial reflection and the uniformity of the velocity of light. Conversely, Newton's main objection to the wave theory of light was that it failed to explain the rectilinear propagation of light. Young pointed out that this objection of Newton's was groundless. Thus, in this paper he opened up the possibility of explaining optical phenomena on the wave theory of light, but it was not until May I8oi that he discovered the principle of interference (8). It was with this principle that he took a decisive step in the development of the wave theory. His explanation of the phenomena which have since come to be known as interference phenomena was far simpler than Newton's complex corpuscular explanation which involved the concepts of'fits of easy transmission' and 'fits of easy reflection'.

Young had also read the Bakerian Lecture of 1800 in which he reverted to his interest in the eye (9). This lengthy paper contained a careful analysis of the eye's optical properties and a description of his improvements to the design of the optometer.

In the summer of i80o Young was considered for the Chair of Natural Philosophy at the Royal Institution. Prior to that time his only writings on natural philosophy covered a small section of the course he was asked to deliver, and this course was devoted in part to the mechanical arts.

The Royal Institution was the brainchild of Count Rumford (1753-1814) who arrived in London in September 1798 with the intention of extending his philanthropic schemes to the metropolis. Rumford enlisted the support of a



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number of eminent men including several members of the Society for Bettering the Condition and Increasing the Comforts of the Poor. At a General Meeting chaired by Sir Joseph Banks (io) a list was read of 58 Proprietors and founder members (ii), each of whom donated 50o towards the proposed Institution. Nine of these gentlemen including Rumford and Banks were chosen to be its first Managers.

Rumford proposed that the Institution should 'bring together the [Natural] Philosopher and those engaged in arts and manufactures' in order to improve industrial and domestic efficiency (I2). These proposals were to be effected through two distinct enterprises. Firstly, by 'the speedy and general diffusion of the knowledge of all new and useful improvements, in whatever quarter of the world they may originate' through the exhibition of manufacturing aids, model kitchens and domestic appliances such as fireplaces. The second enterprise required a laboratory and lecture room where 'the application of scientific dis- coveries to the improvements of arts and manufactures in this country, and to the increase of domestic comfort and convenience' could be taught. The Royal Charter was granted to the Institution in I800.

The first Professor appointed to the Institution in October I799 was Dr Thomas Garnett (I766-I802), who had written several books and had attained a high reputation as a lecturer at Liverpool, Manchester and the Andersonian Institution in Glasgow. Garnett lectured on Natural Philosophy at Rumford's Institution in the spring of I800 and again in the following year. His health was poor and it appears that he was extremely overworked. From the beginning Rumford was not impressed with Garnett and soon it became impos- sible for these two men to work together. Two particular events appear to have occasioned strictures upon Garnett. In one of his lectures he attributed the discovery of galvanism to 'the French', and he was made by Rumford to publicly recant for his egregious politicalfauxpas. Secondly, the syllabus he proposed for his I80I lecture course was not submitted to the Managers for scrutiny and the argument which this sparked off led to his resignation on 15 June of that year.

The next two men hired by the Managers of the Institution were both younger than Garnett and both lacking in public esteem and publications (i3). The first of these was Humphry Davy (I778-I829) from Penzance who had been Dr Thomas Beddoes' assistant at the Bristol Pneumatic Institution since October I798. During this time he had written a book on nitrous oxide (14), contributed several papers to an obscure volume edited by Beddoes (I5) and published several notes in Nicholson'sJournal principally on galvanic electricity (i6). Although not a member of the Royal Society he had several influential



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friends in London. Amongst these wasJ. R. Underwood, a geologist and artist, who became a Proprietor of the Institution and brought Davy to the notice of Count Rumford.

Davy came to London in mid-February i80o, when he was aged 22, to discuss the terms of his employment with Rumford. A month later he settled in a room at the Institution with a salary of I oo a year and the responsibilities of assistant lecturer in chemistry, director of the chemical laboratory, and assistant editor of theJournals. As with Garnett his initial relationship with Rumford was

unfriendly. His appearance and manners were unsuited to polite society, in fact, Rumford arranged a private trial lecture before he would allow his audience to be subjected to this uncouth young man. He delivered three short courses of lectures in the spring of i80o.

With Garnett's resignation in the summer of I80o, the Chair of Natural

Philosophy fell vacant. In Thomas Young, then 28 years old, the Managers found a man very different from Dr Garnett. Furthermore, Young shared at least one important scientific commitment with both Rumford and Davy, this

being to refute the caloric theory of heat (I7). At the time of his appointment Young had been trying to establish a medical practice in London. In this he had little success mainly because he failed to inspire his patients with confidence. Thus, with a considerable amount of time to spare he sought other employment. He frequently attended the meetings of the Royal Society and he was recom- mended to Count Rumford by its President, Sir Joseph Banks.

The result of Young's interview with Count Rumford was a resolution

passed by the Managers on 6 July I80I to hire him as 'Professor of Natural

Philosophy, Editor of the Journals, and Superintendant of the House'. For these duties he was to receive 7300 per annum together with rooms at the Institution. 'I flatter myself' he wrote in his letter of acceptance (18), 'that you will have no reason to complain of any want of zeal on my part in the service of the Royal Institution'. In the same letter he complains,

But I confess I think it would be in some measure degrading both to me and to the institution, that the salary, which appears to me to have been no more than moderate before, should now be reduced one fourth, at the same time that the labour & responsibility of the employment are rather increased than lessened. For whatever might have been expected of the late professor [Dr Garnett] respecting the journals and the superintendance of the house, I do not apprehend that any specific stipulation was made on the subject: and as I am determined to devote a greater share of attention to the institution than he ever appears to have done, I do not see that my education & opportuni- ties of literary acquirement have been such as to render me less worthy than



9i

he was, of a salary which, when compared with the emoluments of other situations of a similar nature, is by no means exorbitant.

His contract at the Royal Institution prevented him from attending to his medical practice although he admitted that he would be 'sorry to bind myself to reject the little that might accidentally fall in my way'.

On 3 August I80I arrangements were concluded and shortly afterwards Young took up residence at the Institution. In the autumn of I 8o he edited the Journals of the Royal Institution. His house duties were probably strenuous although it is difficult to gauge either their extent or his exertion in them. In all probability he worked conscientiously. But his main work during that autumn was the preparation of the Syllabus (19) for his course of lectures which was issued on I9 January 1802. This remarkable work contains over five hundred articles under the three headings of Mechanics, Hydrodynamics and Physics. The fourth part is devoted to mathematical demonstration 'for those who may wish to enter mathematically on the various subjects of the lectures'. This compact octavo volume contains most of the themes which Young later developed both in his lecture courses and in the published Lectures of 1807 (20).

In preparing the Syllabus Young wrote not only on the whole range of natural philosophy but also somewhat more reluctantly on the mechanical arts (21). Andrew Dalzel wrote to Young, 'I can easily comprehend what you tell me about the labour of your Professorship (not a sinecure!). To teach anything publicly to one's satisfaction requires a great deal of previous labour. The field you have had to go over, as appears from your syllabus, is immense' (22).

Young appears to have been well received by Rumford who was still sceptical about Davy's ability as late as September I80I. 'Dr. Young' wrote Rumford, 'promises to be a useful acquisition to us. Davy may do well indeed, if he gets the better of his natural disposition to be idle and to procrastinate' (23).

In 1802 Young delivered three series of lectures. The notes he wrote for these lectures are the subject of the second section of this paper. He delivered seventeen Mechanics lectures on Mondays and Wednesdays at 2 p.m. commenc- ing Wednesday 20 January I802 and he followed these with seventeen Hydro- dynamics lectures beginning on Monday 22 March and ending on Monday 17 May. He read the third course of sixteen lectures on Friday evenings at 8 p.m. between 22 January and 14 May. This course was on Astronomy and Physics. Thus he delivered a total of 50 lectures during that session and reported their contents in the Journals of the Royal Institution (24).

In the first few months of the following year he repeated these courses of lectures although they may then have been extended to a total of 60 lectures. He resigned his post at the Royal Institution in the summer of 1803 but it was



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not until 1807 that the lectures were published (25). This work for which he never received the promised remuneration of I0ooo owing to the bankruptcy of the publishers, consists of two fat quarto volumes. The first volume contains 6o lectures totalling 736 pages and 43 plates, two of which are in colour. The second volume begins with over 450 articles on mathematics, followed by a comprehensive bibliography of 414 pages covering the literature on natural

philosophy, together with reprints of several of his earlier papers and an index. This mammoth work was praised by its reviewers and by subsequent eminent scientists (26). No one can doubt Young's proficiency in many of the subjects on which he lectured.

Unfortunately his lectures before the Royal Institution were not nearly so well received. He soon obtained a poor reputation partly because they were

unfavourably compared with Davy's exciting and entertaining lectures given before virtually the same audience. According to Dr Paris (27), Davy's enthu- siastic biographer, Young 'found the number of his attendants to diminish daily, and for no other reason than that he adopted too severe and didactic a style'. The reviewer in the Critical Review (28) 'heard it asserted that his lectures were

dry and uninteresting. We can readily understand how this must have been unavoidable. He must have been talking an unknown language to the great body of the audience'. Hudson Gurney in his Memoir (29) described Young's style of lecturing as 'compressed and laconic'. The British Critic (30) considered the lectures 'much better adapted to the closet than to recitation before a numerous and very mixed audience'. The reviewer in the Annual Review (3 I) attended the Royal Institution lecture theatre prior to one of Young's lectures, though unfortunately he did not stay to hear the lecture. He was impressed with the apparatus and diagrams and 'could not but applaud the capacities and zeal of the audience, and at the same time admired the assiduity of the lecturer. This reviewer who depended not wholly on hearsay gives the impression that

Young's lectures were well received although he does not state the size or composition of this zealous audience.

Young was all too well aware of his shortcomings as a lecturer particularly when he saw the generous praises which Davy received. He ended his course of lectures on 17 May I802 with the following apology to his audience (32).

With this subject [optics] we conclude for the present our inquiries; but I hope that in another year we shall continue them with undiminished attention and with much greater convenience. I shall not detain you with a long peroration: I am conscious how ineffectual it would be for me to attempt to show that this course of lectures has been all that it ought to have been; and how unnecessary it is on the other hand to assure you that I have not been



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wanting in my efforts to make it less defective. To prepare fifty lectures on

subjects so widely detached from each other, and often so obscure and so little understood in themselves, is a task which instead of four months might well occupy as many years. Under the weight of so anxious and laborious an undertaking it has not been possible for me to arrange a single lecture to my own satisfaction, and my audience has perhaps often been fatigued with

insipidity or disgusted with inelegance. They have been in part indemnified

by the lectures of my colleague [Humphry Davy], who, even in his first course, has been able to unite in an unprecedented degree perspicuity of

theory with brilliancy of experimental illustration. I will not enlarge on what I wish my own lectures to be lest I should hereafter fall short of my professional intentions: but I must at least beg you to consider yourselves as

having been admitted into the study of a painter, while he is tracing the outlines on his canvas, and laying on the first masses of coarse colouring, in a state in which no artist would without reluctance exhibit his productions even to the best judges. Another year I may venture to hope for considerable

improvement; but so much of my time must also be devoted to other

departments of the service of the Institution, that one year will by [no] means allow me to finish every part of my arrangement; and perhaps a state of · . . [?] progressive improvement is all that we ought to require. At any rate, in the month of January next I hope to be somewhat better prepared to solicit your attention and approbation. The year of 1802 brought two considerable changes to the Royal Institution,

but neither of these directly concerned Young. The first transformation related to Davy who emerged as the central attraction at the Institution. He was no longer the awkward provincial youth, shunned by polite society, whose lectures in I8oI were described as 'desultory'. Instead, his introductory lecture delivered on the afternoon of 2I January 1802 was enthusiastically received by a 'crowded and enlightened audience'. Thereafter Davy attracted the famous and fashionable to the Royal Institution and he was frequently made the guest of honour at polite dinner parties.

The second major change was related to the power structure at the Institu- tion. Rumford, in league with SirJoseph Banks, maintained his iron grip on the management while he was in London. He spent two months on the Continent towards the end of I80I and finally departed from England on 9 May 1802. It

appears that Rumford quarrelled with some of the other Managers including Thomas (later Sir Thomas) Bernard and SirJohn Cox Hippisley. This argument seems to have been over the basic aims of the Institution and probably hastened Rumford's departure, after which he took little interest in its affairs.



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When he formed the Institution Rumford realized the necessity of courting the rich and famous in London in order to finance his philanthropic plans. For this reason he admitted the wealthy to 'fashionable' lectures while utilizing the workshop and repository of models for more mundane purposes. It seemed likely that if this balance could be maintained the whole venture would prosper, and in this aim Sir Joseph Banks supported him. But Bernard and Hippisley, who was already notorious for his social engineering (33), were only interested in attracting the aristocracy in order to benefit their own social standing. They seized their opportunity as soon as Rumford departed and 'within a month . . . his best works were destroyed' (34). The men working on the models were dismissed and much of the apparatus was removed from the kitchen, workshop and laboratory. Mr Webster, the draughtsman whose school for mechanics was discontinued, wrote (35):

I was asked rudely (by an individual I shall not now name) what I meant by instructing the lower classes in science. I was told likewise that it was resolved

upon that the plan must be dropped as quietly as possible. It was thought to have a dangerous political tendency, and I was told that if I persisted I would become a marked man! . .. Count Rumford left England about the same

time, certainly neither rewarded nor thanked in proportion to the good he had done. The management of the Institution now fell into other hands. . In short, it might seem as if the managers had resolved that the Institution should not be for the application of sciences to the common purposes of life. Sir Joseph Banks was Rumford's main supporter at the Institution during

this period but his health was poor and he was forced to share his time among the several organizations with which he was connected. He resigned from the

management of the Royal Institution in 1804. 'It is now entirely in the hands of the profane' he wrote to Rumford (36), and it is 'perverted to a hundred uses for which you and I never intended it' (37).

Throughout this period the public image of the Royal Institution also

changed. Initially it was ridiculed by the more conservative members of society because it violated certain social conventions. Science was part of the cultural

heritage which was traditionally vested solely in the upper classes. Some of the more enlightened members of the aristocracy appreciated the value of dissemi-

nating scientific knowledge to everyone. But generally the idea of sharing this valuable heritage with the less respectable members of society caused a social scandal, particularly when the nobleman, his gardener and the newly-rich manufacturer attended the same Institution. James Gillray cleverly caricatured the proceedings at the Institution (Plate 3). His customers were probably most amused by the fact that the respectable members of the audience received the



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demonstration with scholarly dignity whereas the lower classes witnessed the humiliation of Sir John Cox Hippisley with raucous guffaws. Lady Holland noted in her diary the social gossip surrounding the Institution (39).

This Institution of Rumford's furnishes ridiculous stories. The other day they tried the effect of the gas [nitrous oxide], so poetically described by Beddoes; it exhilarates the spirits, distends the vessels, and, in short, gives life to the whole machine. The first subject was a corpulent, middle-aged gentleman, who, after inhaling a sufficient dose, was requested to describe to the company his sensations; 'Why, I only feel stupid.' This intelligence was received amidst a burst of applause, most probably not for the novelty of the information. Sir Coxe Hippisley was the next who submitted to the operation, but the effect upon him was so animating that the ladies tittered, held up their hands, and declared themselves satisfied (40). The experiment to remove the popular prejudice in favour of silver teapots failed, as the thermometer gave the lie to the Professor's [Garnett's] learned dissertations, but it must have been from the malice of his evil genius, for the fact is in his favour. The upper classes inherited the concept of pure science studied for its own

sake without any relation to practical applications. Bernard and Hippisley knew that the different social classes could not share the Institution. They turned the Institution into a respectable centre for polite society and it was this facet of the Institution which was ridiculed by the new radicals who had a democratic

approach towards science. Francis Horner on a visit to the Institution in March 1802 noted that 'The audience is assembled by the influence of fashion merely; and fashion and chemistry form a very incongruous union' (4I). Similarly Henry Brougham disparagingly associated the Royal Institution with 'fashionable science' suitable for the whims of ladies.

Young and Davy, neither of whom were vested with any power, were

trapped in the politics of the Institution. All decisions were taken by the Managers to whom Young and Davy had to apply for every concession. Fur- thermore, the Managers wielded power over the professors and could dictate the genre of science taught and practised at the Institution. While Rumford was still at the Institution Young progressed, worked hard and was respected for his abilities although he found Rumford 'had too great a propensity to dictate without sufficient regarding the opinions of those who were of equal authority with himself (42). Instead the new Managers required only that he amuse the subscribers to the Institution and in this he was certainly no asset to them. He already had a poor reputation as a lecturer. A further indignity occurred in January 1803 when the second number of the Edinburgh Review was published



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containing two anonymous and vituperative articles (by Henry Brougham) attacking two of Young's optical papers in the Philosophical Transactions (43). These reviews probably caused Young's popularity with the Managers to diminish further. Moreover, his optical theories provoked opposition in the

Royal Society mainly because he clumsily refuted the corpuscular viewpoint associated with the lauded name of Newton. Most of the reviews criticized him on this point rather than on any intrinsic deficiency in the wave theory of light. Young's sensitivity to criticism is shown in this extract from a letter dated 26 October I802 from Humphry Davy to Davies Giddy (44).

Have you seen the theory of my colleague, Dr. Young, on the undulations of an Ethereal medium as the cause of Light? It is not likely to be a popular hypothesis after what has been said by Newton concerning it. He would be

very much flattered if you could offer any observations upon it, whether for or against it. After Rumford's departure in May I802, one of the first resolutions passed

by the Managers was to appoint Davy as Professor of Chemistry. It is not

suggested that Davy took sides in the dispute between Rumford and Bernard, but the prowess he gained as a lecturer in I802 brought public renown to the Institution. Thus he assisted Bernard's cause by acting as a figure-head and attracting the wealthy and famous to the 'reformed' Institution.

There is evidence that Young and Davy were close friends but this evidence

probably relates to their later collaboration in the Royal Society where Young was Foreign Secretary and Davy held the post of Secretary and later became President. It is reasonable to suppose that during the two years they spent to-

gether at the Royal Institution, no such friendship developed. Their relationship was probably cool although courteous. Young had every reason to be jealous of Davy who had gained the social prestige after which he himself eagerly sought. In his lectures Young unfavourably compared the poet with the natural

philosopher (45) and this may have been a veiled attack on Davy who was also

respected for his poetic accomplishments. In Dr Paris's biography of Davy the following passage occurs which explicitly states their relationship at the Royal Institution (46). 'With Dr. Garnett he [Davy] had lived on terms of great intimacy; with his successor [Young] he associated with less ease and freedom.'

In I802 Young made several requests to the Managers which were granted. He was given two months' leave of absence during the summer when he took advantage of the intermission in the Napoleonic wars to visit Rouen as the Duke of Richmond's physician. His requests for books and apparatus were granted including orders for a whirling table and a solar microscope.

During the following year his position deteriorated. His courses excited



James Gillray's caricature of the proceedings at the Royal Institution (38)



A double-page from Young's manuscript lecture notebooks. Notebook, I6/I7v; I6/I7r



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little interest and were probably poorly attended. On 2I April I803 he made a further petition to the Managers (47) which included the request for a rise in salary and an inquiry relating to the employment of a librarian and a reference librarian. At the Managers' Meeting held five days later these proposals were utterly rejected but for some reason, probably political, this resolution was not communicated to Young until 6June. When he received this reply he expressed his wish to resign. The Managers invited him to deliver twenty further lectures on his own terms but he declined. At their next meeting they agreed to termi- nate his engagement and to pay him the salary owing, which may have been a considerable sum. Later (3 October I803) they offered him life membership of the Institution which he cordially accepted. Thereafter he maintained no further contact with the Institution (48).

Young resigned from the Royal Institution under a cloud. In his reply to the Edinburgh Reviewers (49) he stated that he found 'the duties of the Professor- ship so incompatible with the pursuits of a practical physician, that, in compli- ance with the advice of my friends, I gave notice of my wish to resign the office'. He probably made this statement in order to avoid incurring any damage to his reputation as a physician. However, it does not give a sufficiently plausible reason why Young should have resigned a post closely connected with his research interests. The changing situation at the Royal Institution would seem to have been a major contributory factor if not the motive for his resignation. We have seen that by 1803 the Royal Institution catered almost solely for 'fashionable' science in which Young could play no active part. His lectures were unsuccessful, his papers at the Royal Society were not well received, he was being scurrilously attacked in the Edinburgh Review and he was not on close terms with Davy. The Managers who appear to have granted Davy's every whim were obviously unhelpful to Young to the point of hindering his social and scientific progress. Moreover, they appear to have paid him neither promptly nor the amount he demanded. The several weeks taken to notify him of their refusal to grant his requests may indicate an even more hostile attitude. He obviously did not fit into the new style of the Institution. Thus I would suggest that he resigned not in order to develop his medical practice, but rather because he was forced out of the Institution and consequently fell back on his original intention of becoming a physician.

His practice was hardly successful and thereafter he wrote widely on a considerable range of subjects including the mechanical arts. In 1804 he was elected Foreign Secretary of the Royal Society and continued to be an active though reserved member of London's scientific community.



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II The notes which Young wrote for his lectures at the Royal Institution are

contained in exercise books measuring approximately 7- by 9 inches with red covers. Twenty of these books numbered in pencil from 2 to 21 are now in the

Library of University College London (50). His notes for the Mechanics lectures are contained in notebooks 2 to 12 and presumably the missing notebook contained the notes for his introductory lecture delivered on 20 January I802. The subsequent four notebooks contain all the Hydrodynamics lectures. No complete record remains of the first two Astronomy lectures (5I) delivered on 22 and 29 January but the rest of the Astronomy and Physics lectures are recorded in books 17 to 21.

He found 'that it was most eligible to commit to writing, as nearly as possible, the whole that was required to be said on each subject .. .' (52). There- fore, the notes contained in the lecture notebooks are probably an accurate record of Young's lectures at the Royal Institution. The notebooks were begun late in I80I when Young cut out articles from proof copies of the Syllabus (53) and keeping them in order glued them to the right-hand pages of the notebooks.

Young added the rest of the substance of his lectures to these articles, sometimes

spreading over to the facing page. Usually these additions amounted to an elaboration of the contents of the article, but sometimes he added extra topics and digressions. He occasionally included apposite extracts from the mathematical section of the Syllabus but generally he omitted mathematical discus- sions as he considered them unsuited for the lecture theatre. Furthermore, he made reference to the several demonstrations which he intended to make during each lecture (54). He tried to make the subject interesting for his audience and he appears to have placed great emphasis on the experimental demonstrations he performed.

Some of the passages in Young's earlier lectures appear in the large and neat hand in which he wrote his correspondence, but the majority of the notes are written in a much smaller script which sometimes degenerates into illegibility. His writing cannot be used to date specific passages with any accuracy although it is sometimes obvious where two consecutive passages were written at different times. The deterioration of his style of writing may correspond to the increasing pressure of his work and perhaps to the demoralization which he felt as he realized his failure as a lecturer at the Royal Institution.

It is difficult to assess the amendments he made to the notes in 803 when he repeated his lecture courses and when, according to Peacock (55), he increased the number of lectures to 6o. At that time he may have added some material to



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the notebooks and it is also possible that he made further subsequent amendments. The reports of his 1802 lectures which appear in theJournals of the Royal Institution, though not exhaustive, show less emphasis on certain subjects than appears in the notebooks. In particular, the lectures on the History of Science, written on vacant left-hand pages, appear to be innovations which were probably introduced in 1803. It is reasonable to assume that the majority of the notes date from late I80o and early 1802.

The Syllabus and the vast majority of the notebooks were written in less than a year. This was no mean achievement since Young had little formal education in natural philosophy and during the same period he was actively engaged in optical research and carried out his duties at the Royal Institution. Most of the material in the notebooks is not original. When he dealt with a subject like natural history in which he had no great interest he merely reiterated the views of the more competent practitioners of that subject. Even his lectures on the mechanical arts are composed almost entirely of descriptions of machines taken from other sources (56). Young was primarily interested in natural philosophy and it was as a natural philosopher that on occasions he was able to suggest improvements to the mechanical arts. For example, he showed his audience the best form of construction for arches and demonstrated the most efficient method of carrying large and heavy objects (57). In his lectures on the application of scientific principles to practical subjects he drew heavily on Continental authors and was one of the first to introduce into England the advances made by French engineers in the previous century. The subjects to which he devoted the greatest attention were those connected with his own research interests. He took greatest pride in presenting his original contributions to optics and acoustics.

Young claimed that for the three years following his resignation from the Royal Institution he made improvements to the lectures and compiled his bibliography of the literature on natural philosophy. The Lectures were even- tually published in I807 and it is instructive to compare their contents with the contents of the lecture notebooks dating from some five years earlier. It is immediately evident that large tracts of the lecture notebooks appear verbatim in the published form. Hence, the notebooks were probably still in his possession when he was preparing his manuscript for the publishers.

The notebooks give some indication of Young's mentors (58). It is not sur-

prising to find that Newton is highly and frequently praised. It is more surprising to find that Hooke is not only frequently quoted but on several occasions is treated with the reverence usually reserved for Newton alone. For example, in reference to the undulatory theory of light, Young wrote the following passage which does not appear in the Lectures. 'Dr. Hooke . . . this most ingenious



I00

philosopher was unfortunately too deficient in mathematical knowledge: in every other qualification he was little if at all inferior to his great contemporary Newton' (59). Young's enchantment with Hooke's writings had a detrimental effect on his own reputation. He did not believe Newton to be infallible whereas Newton's writings were thought to be impeccable by many philosophers at the

beginning of the nineteenth century. His implication that Newton might be

capable of the slightest mortal failing was sufficient to enrage the critics. Their

disapproval descended on Young when he demonstrated the shortcomings of the corpuscular theory in his optical memoirs, despite his attempt to stamp the wave theory with Newton's authority. However, in the notebooks Young was more honest about his allegiance to Newton's writings and he did not cite Newton's name in support of his own theory of light. Instead he took a much more objective view of Newton's works and readily admitted on several occasions that Newton had erred. At the time of writing the notebooks Young was

particularly interested in the controversial problem of the ether. He expressed the opinion that Newton, in the Queries to the Opticks,

proceeds from the supposition of an elastic medium pervading all space, a

supposition which he advances with considerable confidence, and which he

supports with very strong reasons; but which I will venture to say, and I trust that the opinion will soon become general, has been confirmed by arguments so convincing, that combining them with what has already been stated by Newton, we may be fully justified in considering the existence of such a medium as established. ... (60) During the first few years of the nineteenth century Young engaged in

several research topics-principally optics, cohesion and the strength of materials (6I). These were intimately connected with the basic changes which took place in his natural philosophy relating to the explanation of action at a distance. He

experienced considerable difficulty in forming the concept of action at a distance and in his notebooks we find that he tried to reduce this concept to the interaction between particles of matter and subtler particles of which ethereal media are composed. Furthermore, it appears that he was attempting to construct a

large portion of his natural philosophy on an analysis of pressures exerted on a universal ether. His use of the ether will be briefly examined and it will be shown how his concepts changed during the period under discussion (62).

In his memoir to the Royal Society of 1799 (63) Young proposed that a rare and highly elastic ether pervades the Universe and that this ether is composed of subtle particles which mutually repel one another and are attracted to particles of matter. Thus he believed the ether to be denser in dense bodies than in rare ones and that it forms 'atmospheres' around material bodies. He proposed that



IOI

vibrations in this ether constitute light and radiant heat and in his two earliest optical papers (64) he explained some optical phenomena by the concept of the ether being denser near material bodies. For example, when a body is placed in a beam of light, the light passing closest to the body is retarded by the ethereal atmosphere and the whole beam diffracted into the body's shadow.

In the notebooks we find that he tried to apply this hypothesis of the ether in order to explain a much wider range of phenomena. In particular he identified the ether as the cause of cohesion and repulsion between particles of matter. The concept of atmospheres of ether surrounding material bodies occurs again in his discussion of electricity. The electric fluid is distributed so that it forms atmospheres around positively charged bodies. Furthermore, he tried to identify this fluid with either the ether or some manifestation of it. Magnetism could not be aligned with his scheme since he could not explain why the magnetic fluid was attracted only to bodies containing iron. Moreover, he experienced the greatest difficulty in assigning a mechanical cause to gravitation. Despite his attempts he was unable to reconcile gravitation with his hypothesis that the ether is denser near material bodies (65). Young speculated that most physical phenomena were connected with the interaction between a universal ether and matter. For example, he speculated that electrical phenomena 'may depend on some modification of the actions of the medium [the ether] which appears to be concerned in the effects of light, heat, cohesion and repulsion . . .' (66).

It was during the second year of his appointment to the Royal Institution that Young first expressed serious doubts about the validity of his hypothesis concerning the distribution of the ether. But it was not until November 1803 that he publicly rejected this hypothesis (67). The published Lectures of 1807 show little sign of his earlier commitment to the concept of the ether being more dense near material bodies. He did not explain any phenomena by this concept and now employed the ether solely as the vehicle of light and radiant heat. He still experienced difficulty in conceiving of action at a distance and on a few occasions he conjectured that action at a distance could be reduced to mechanical causes.

Having briefly delineated the major change which took place in Young's natural philosophy during the first few years of the nineteenth century, I shall now discuss two of Young's research interests dating from the same period. At the time of writing the notebooks his main research interest was in optics and more particularly in the nature of light and colours. He had discovered the principle of interference in May I80I and during his first year at the Royal Institution he was trying to apply this principle to explain several optical phenomena.



I02

A note of particular relevance to the progress of his optical researches appears in the notes for the lecture he delivered on 17 May I802. Here (68) he stated that he had recently 'observed two other cases of the production of colours which have been hitherto wholly unnoticed'. The first of these phenomena was the appearance of colours around a hair or fibre held close to the eye. He explained these colours in terms of'the portions of light spreading from op- posite sides of the hair .... The second fact, which occurred to me only two days ago [15 May], is the existence of coloured rings of much larger dimensions than usual, when a little moisture is interposed between two pieces of glass nearly flat . .. now these fringes can only be produced by the interference of two portions of the same light, one passing through the air, and the other through the water'. On this explanation he predicted that the coloured rings produced should be about six times larger than those formed by the plates of glass when

separated by the same thickness of air alone. He then proceeded to verify this prediction. These two experiments formed the basis of the paper he read before the Royal Society on I July that year (69).

In the Syllabus (70) Young noted that Newton had attributed the phenomenon of atmospheric halos to refraction. To this explanation Young added the conjecture that they might be caused by inflection. When he dealt with the subject of halos in the notebooks he observed that the two experiments cited above bear a close resemblance to the formation of halos. He assumed that water droplets were essential to the creation of halos, the cause of which he sought to

explain by analogy with each of the above experiments in turn. If the formation of halos were analogous to the first of these experiments then no light would be

required to pass through the water droplets, but if their formation were analogous to the second case then a portion of the light would pass through the water. Thus he had two distinct and contradictory hypotheses on which to

explain halos. In his subsequent papers he did not propose any explicit explanation of them, but in the published Lectures he attributed their formation to the refraction and reflection of light from snow crystals and noted that he had arrived at this explanation independently of Mariotte (7I).

Another problem which Young never satisfactorily resolved was how to explain chromatic dispersion by refraction on the wave theory of light. In the memoir of I8oi (72) and in the notebooks (73) he explained dispersion by the effect on transmitted light of the vibrations in the particles of transparent bodies. These vibrations depend on the temperature of the body and are slower than the vibrations of the ether which constitute light. Thus he considered that when light enters an optically denser medium it is retarded but some wavelengths are retarded more than others and dispersion takes place. It is surprising to find that



103

a few weeks later (74) he adopted a very different explanation of dispersion. He now considered that part of the incident light passes through the ultimate particles of matter which are in a state of vibration. For a reason which he did not explain the portion of light passing through the particles of matter is selec- tively retarded, and after it has passed through the body it interferes with another portion of light which has passed through the pores between the particles. Dispersion is then produced because the direction in which constructive interference takes place depends on the wavelength of the light. In 1807 he admitted the difficulty of explaining dispersion on the wave theory of light (75). He put forward the conjecture that the phenomenon results from the different velocities of propagation of different coloured light in a compressible medium. In a vacuum the ether is pure and incompressible, thus all light is propagated with the same velocity. However, in a material substance, the ether is mixed with particles of the substance. He supposed that the effective medium through which the light is propagated is no longer incompressible and the velocity of the light is no

longer constant but depends on its colour. Therefore, when light passes into a denser medium the different colours are refracted at different angles in accord- ance with Huygens' construction and dispersion takes place.

To find an explanation for dispersion proved to be one of the most difficult

problems which Young encountered when he first proposed the wave theory of

light. Three explanations have been mentioned which he proposed over a period of about six years. These explanations illustrate his tendency to propose in-

genious ad hoc hypotheses to overcome any difficulty which he encountered in his natural philosophy.

Intimately connected with his discussion on the nature of light was his

explanation of the cause of diffraction. His earlier memoirs show that he was undecided whether the ethereal atmosphere surrounding material bodies was the cause of diffraction or whether diffraction was a natural property of light. He became progressively more convinced that ethereal atmospheres are not concerned in diffraction. The notebooks mark an important point in this discussion for he concluded, with only very slight reservations, that the diffraction of light into the geometrical shadow of a body 'arises as Dr. Hooke supposed

. .principally from the natural tendency of light to diverge in all directions'

(76). This explanation represented an important step in his optical theory. No

longer was the ether the principal agent for producing optical phenomena. Instead, with the reduction of the importance of the ether, Young was able to take a more dynamic approach to optics and in particular he paid more attention to light waves. Although Fresnel later solved the problem of diffraction mathematically, Young approached the problem from a very different point of view.



104

He was concerned with the mechanism which caused optical phenomena. Initially, he tried to find this mechanism in the substance of propagation (the ethereal medium) and when this failed he turned his attention to the 'qualities' of the waves constituting light.

Young first mentioned in the published Lectures the experiment which has since come to be known as Young's slits or Young's fringes (77). He explained the formation of these fringes by the divergence of light after it had passed through one of a pair of slits. The two series of secondary wavefronts emanating from these slits then interfered to produce a fringe pattern. This explanation required a clear concept of the nature of wavefronts and an appreciation of how interference could be represented in terms of wavefronts. In his earlier writings Young explained diffraction by considering two rays of light emanating from the same point and arriving at a second point by slightly different paths, having been acted upon by the denser ether surrounding the diffracting body. They interfered and produced either brightness or darkness dependent on the path difference incurred. In taking this view he was limited by his adherence to the

concept of the ether. In moving away from the preoccupation with the distribution of the ether his concepts involved in the wave theory of light also changed. Initially, he could only apply the principle of interference to rays of light but

gradually he accepted a more dynamic interpretation in terms of wavefronts. It appears that in 1802 his views on the subject were being radically reformed. The ether still played an important role in his natural philosophy but he was

beginning to realize its limitations and had almost accepted Hooke's explanation of diffraction. This explanation was part of the more dynamic approach which culminated in his rejection of ethereal atmospheres and in his new appreciation of interference phenomena.

Despite the imperfections in his wave theory of light in 1802, his notebooks give some indication of the depth of his commitment to the wave theory and the principle of interference. In the first lecture on Hydrodynamics (22 March), he anticipated the lectures on sound and light, 'subjects to which I look forward with particular pleasure' (78). When he reached the discussion on the nature of light and colours he set beside Newton's speculations 'a favourite system of my own' (79). He believed that the principle of interference could be applied to explain not only the colours formed under certain conditions, 'yet its greatest importance appears to be its immediate tendency to give us information respecting the nature of light & of course that of heat also' (80). Time alone, he considered, would bring about the confirmation or rejection of his theory. He added, 'I am happy to say that one [philosopher] in particular, whose judgment in all optical subjects must always be received with respect, has borne public



I05

testimony to the sufficiency of the explanation & to the probability in [?] the theory' (8I).

Young's optical researches have overshadowed another subject which

engaged his attention during almost the same period. This investigation concerned cohesion which also interested several other eminent philosophers including Monge, Laplace andJohn Leslie at approximately the same time. The results of Young's investigation of cohesion were presented before the Royal Society on 20 December 1804 (82). In contrast to the opinions expressed in that

paper, the notebooks contain a very different approach to the subject of cohesion. His earlier view was connected with his hypothesis concerning the attraction of ether to particles of matter.

Matter he considered to be composed of particles which are impenetrable to one another. A repulsive force acts between these particles, which is demonstrated

by the resistance of gases to compression. Under normal conditions the repulsive force also prevents two solid bodies in contact from fusing into a single mass.

Young cited the experiment of two glass plates being brought close to one another so that an external pressure is required to overcome the repulsive force and to bring them into intimate contact. Professor Robison found that a pressure of a thousand pounds per square inch was required to 'produce the greatest possible degree of contact' (83). In his notebooks Young utilized his hypothesis that a layer of dense luminiferous ether surrounded material bodies to account for this phenomenon. He suggested that this layer of ether covering the surfaces of the glass plates would satisfactorily account for the force of repulsion between them.

The two glass plates can be brought into intimate contact, so that they no

longer repel each other, either by heating them or by applying 'pressure united with friction'. In terms of Young's model this second effect is represented by the

displacement of the ether which covers the external surfaces of the glass plates into the pores between the particles composing the plates. Once intimate contact has been achieved the plates cohere and require an external force to part them. Young considered that this cohesion was due to the pressure of the ether on the external surfaces of the plates. He had in mind the analogy between the

pressure of the ether on the glass plates and the pressure of the air on the external surfaces of two Magdeburg hemispheres in contact with one another when the

pressure inside them has been reduced.Just as an external force is required to part the hemispheres, so an external force is also required to separate two cohering glass plates. Hence Young was able to describe repulsive and cohesive pressures by applying his hypothesis relating to the distribution of the ether.

Young postulated that the repulsive force acting between two particles of



io6

matter varies inversely as the distance but 'ceases at a given distance'. However, he found it more satisfactory to conceive of cohesion and repulsion by analogy with atmospheric pressure rather than in terms of abstract forces acting at a distance. He applied his views on cohesive and repulsive forces to practical problems in his lectures at the Royal Institution. He considered that the force of friction 'arises principally from cohesion' (84) and he attributed the strength of materials to 'the cohesive and repulsive force of their particles' (85). The lecture notebooks contain no mention of the modulus of elasticity which is usually connected with Young's name and which appears in the published Lectures of 1807 (86). By that time he had introduced the concept of'lateral adhesion, or

rigidity, which is opposed to the internal displacement of the parts of a single body' (87). Furthermore, he proposed that this lateral adhesion between particles of matter is closely connected with the force of friction. The concept of lateral adhesion represented another departure by Young from his earlier preoccupation with the static concept of the ether.

In the section of the notebooks dealing with cohesion Young was primarily interested in the mechanism holding together particles of rigid substances. He explained both repulsion and cohesion in terms of the actions of ethereal atmospheres which he supposed to surround material bodies. He first expressed serious doubts about the validity of this hypothesis during the summer of 1802 when he rejected the role of the ether in his explanation of cohesion (88). This explanation was inconsistent with the principle of the free passage of the ether through material bodies because he considered that on the wave theory of light the ether had to be at rest in the universe to account for stellar aberration. Subsequently Young made no use of the ether in his discussion of cohesion and repulsion.

In his paper of 1804 (89) and in the published Lectures (go) he concentrated on a very different aspect of the subject. He was now concerned with the cohesion of fluids, capillarity, the forces between particles composing a fluid, and the forces between particles of a fluid and those of a neighbouring solid. He introduced two major innovations in 1804. Firstly, he found 'that for each combina- tion of a solid and a fluid, there is an appropriate angle of contact between the surfaces of the fluid, exposed to the air, and to the solid' (9I). He then related the cohesion between the particles of the fluid to the form and tension of its surface. His second innovation related to the cause of cohesion and repulsion. He explained these phenomena solely in terms of two short-range forces, a repulsive force and a cohesive force, which he did not reduce to mechanical causes.

We may suppose the particles of liquids, and probably those of solids also, to possess that power of repulsion, which has been demonstratively shown by NEWTON to exist in aeriform fluids, and which varies as the simple



I07

inverse ratio of the distance of the particles from each other. In airs and

vapours this force appears to act uncontrolled; but in liquids, it is overcome by cohesive force, while the particles still retain a power of moving freely in all directions; and in solids the same cohesion is accompanied by a stronger or weaker resistance to all lateral motion [lateral adhesion], which is perfectly independent of the cohesive force, and which must be cautiously distin-

guished from it. It is simplest to suppose the force of cohesion nearly or

perfectly constant in its magnitude, throughout the minutest distance to which it extends, and owing to its apparent diversity to the contrary action of the repulsive force, which varies with the distance (92).

REPULSIVE FORCE

-uO^~ ~ ~~~ \ ': -

'A ATTRACTIVE (COHESIVE) o ~,_----^ -->.,- FORCE

I I

A B HK G C SPACING BETWEEN PARTICLES

FIGURE I. Young's graph of inter-particulate forces (93)

He was able to explain a number of phenomena by the action of these two forces. In particular he arrived at a solution to the problem of capillarity in terms of the angle of contact between the surface of the liquid and a capillary tube. In the Lectures he illustrated his theory of the cohesion of liquids with several

practical examples. Again in his discussion of cohesion we see that Young moved away from his

attempt to describe the phenomenon by the existence of ethereal atmospheres. Instead of explaining cohesion by an ethereal mechanism which is governed by a set of laws and trying to determine these laws, he simply posited a force to

explain the phenomenon. Similarly repulsion was reduced to a force. He was then free to explain a whole range of observable phenomena and to discuss the relations between these phenomena.

Young's lecture notebooks in themselves may not be of tantamount importance as the majority of their contents appear verbatim in the published Lectures but they do help to throw greater light on the development of his concepts. They add to our knowledge not only of his theory of light in I80I-I802 but



io8

also of all the other subjects which he covered in his lectures at the Royal Institution. In particular, they help to clarify the role of the ether in his early philosophy, a concept which appears to have preoccupied him. Only after he had rejected this hypothesis of the ether were his ideas able to progress.

ACKNOWLEDGEMENTS

I am indebted to the Librarian of University College London for permitting me to cite passages from Young's lecture notebooks and to reproduce a photo- graph of a double-page from these notebooks. The Librarian of the Royal Society is gratefully acknowledged for his permission to allow me to quote an extract from a letter from Count Rumford to Sir Joseph Banks. I should like to thank the Trustees of the British Museum for permitting me to quote from letters in the Banks and Napier Papers and also to reproduce the cartoon by James Gillray.

NOTES

(I) The contents of these notebooks have not previously been analyzed. (2) For details of Young's formative years see George Peacock, Thomas Young, M.D., F.R.S.,

&c. (London i855) or Alexander Wood, Thomas Young, Natural Philosopher (Cambridge I954). Also there are several biographical sketches of Young.

(3) Young, 'Observations on Vision', Phil. Trans., 83, 169-181 (I793). This paper was read before the Royal Society on 30 May 1793 when Young was only I9 years old.

(4) For an interesting sociological study of scientific education see Nicholas Hans, New Trends in Education in the Eighteenth Century (London I951).

(5) De Corporis Humani Viribus Conservatricibus defended i6July 1796. (6) Letter to Andrew Dalzel (Professor of Greek at Edinburgh University) dated 5 July I797.

Published in Dalzel, History of the University ofEdinburgh (Edinburgh 1862), I, I44.

(7) Young, 'Outlines of Experiments and Inquiries respecting Sound and Light', Phil. Trans., 90, Io6-I5o (I8oo). Read I6 January I8oo.

(8) Young first published the principle of interference and applied it to explain several phenomena in his paper 'On the Theory of Light and Colours', Phil. Trans., 92, 12-48 (1802). This was read as a Bakerian Lecture on I2 November I80I.

(9) Young, 'On the Mechanism of the Eye', Phil. Trans., 91, 23-88 (i8oi). (Io) Sir Joseph Banks (I743-I820) was President of the Royal Society from I778 to 1820.

Initially he was opposed to Rumford's Institution but he was soon won over to support its cause. In April I802 the Council of the Royal Society agreed to permit extracts from papers communicated to the Society to be published in the Journals of the Royal Institu- tion.

(II) Of these 58 Proprietors 29 were titled, I8 were Members of Parliament and I8 were Fellows of the Royal Society. Count Rumford and Henry Cavendish were the most eminent scientists in the group. Mathew Martin, F.R.S. acted as secretary to this meeting although his name does not appear on the list.



I09

(12) Rumford, Proposalsforforming by subscription in the Metropolis of the British Empire, a Public

Institutionfor diffusing the knowledge andfacilitating thegeneral introduction of Useful Mechani- cal Inventions and Improvements, andfor teaching, by Courses of Philosophical Lectures and

Experiments, the application of Science to the Common Purposes of Life (London 1799). Re-

printed in Proceedings of the Royal Institution, 6, ix-xxxii (1872). (I3) Rumford proposed that 'none but men of the first eminence in science' should be invited

to lecture at the Institution. Ibid., xxi.

(14) Davy, Researches, Chemical and Philosophical; chiefly concerning Nitrous Oxide, or Dephlogisti- cated Nitrous Air, and its Respiration (Bristol 1800).

(I5) Contributions to Physical and Medical Knowledge, principallyfrom the West of England, edited

by Dr T. Beddoes (Bristol 1799). (I6) Nicholson'sJournal, May 1799, 55-59; February I8oo, 515-518; September 800o, 275-281;

November 80oo, 337-341 and 380-381; December I800, 394-402.

(17) 'This opinion [that heat consists in vibrations of the particles of bodies] has of late been much abandoned. Count Rumford, Professor Pictet, and Mr Davy, are almost the only moder authors who have appeared to favour it; but it seems to have been rejected without any good grounds, and will probably very soon recover its popularity.' Young, op. cit. (8), 32.

(18) Letter from Young to Count Rumford dated 9July I80o. British Museum, Banks' Corres-

pondence, Add. MS. 52281, fol. 30.

(I9) Young, A Syllabus for a Course of Lectures on Natural and Experimental Philosophy (London I802).

(20) Young, A Course of Lectures on Natural Philosophy and the Mechanical Arts (London 1807). Hereafter this work will be referred to as the Lectures. A second edition edited by Rev.

Philip Kelland was published in 1845. (21) In I816 Young wrote to McVey Napier, '. . but for the last Io years, I have paid no

attention to the mechanical arts in any form, nor do I wish to renew my acquaintance with them-preferring generalinvestigations to particular applications'. British Museum, Napier Papers, Add. MS. 34611, fol. 407.

(22) Dalzel, op. cit. (6), I, 208. This letter is dated 20 July I8o0, hence the syllabus referred to is not the Syllabus, op. cit. (I9).

(23) Letter from Count Rumford to SirJoseph Banks dated 21 September I80o. Royal Society, Misc. MSS. 9.7.

(24) Journals of the Royal Institution, I, 85-89, 103-109, 167-170, 197-202, 218-227 (1802).

(25) Op. cit. (20). (26) For example, one reviewer described the Lectures as a 'splendid, extensive and profound

work'. Critical Review, 12, 2 (1807). Sir Joseph Larmor considered them to be 'the

greatest and most original of all general lecture courses'. Nature, 133, 276 (I934). (27) J. A. Paris, The Life of Humphry Davy (London 1831), p. 93. (28) Critical Review, 12, 2 (1807). (29) H. Gurney, Memoir of the Life of T. Young, &c. (London 1831), p. 21.

(30) British Critic, 25, 97(January 1805). (3I) Annual Review, 7, 673 (i8o8). (32) Notebook I6/2Ir; I6/2Iv. For nomenclature see n. 50.

(33) He was knighted in 1796 for arranging the marriage between the Duke of Wurtemberg and the Princess Royal. It is interesting to note that he was elected to the Royal Society



IIO

in June 800o, which neatly coincided with his involvement in the politics of the Royal Institution.

(34) Henry BenceJones, The Royal Institution, its Founder and its First Professors (London 1871), p. 200.

(35) Ibid., p. I94.

(36) Letter from Banks to Rumford dated April 1804. Ibid., p. 261.

(37) Letter from Banks to Rumford dated 6 June 1804. Ibid., p. 263. (3 8) The lecturer is almost certainly Thomas Gamett although he has sometimes been identified

as Young-see M. D. George, The British Museum Catalogue of Political and Personal Satires (London 1947), 8, I12-II3. His assistant is Humphry Davy and Hippisley is the

guinea-pig. Rumford stands at the far right and among the other notables are Lord

Stanhope (with eye-glass) and Sir Henry Englefield (notebook in hand). A group of less respectable auditors stand at the far left. Gillray probably based his cartoon on the incident mentioned by Lady Holland (n. 39) which occurred in I8oo before Davy arrived at the Institution. On 20 June i8oi Davy alone demonstrated the effects of nitrous oxide. Therefore this cartoon published on 23 May 1802 does not faithfully depict any specific event at the Institution but rather conveys a general impression.

(39) Entry for 22 March I8oo in The Journal of Elizabeth, Lady Holland, ed. by the Earl of I1- chester (London 1908), 2, p. 60-6I. Lord Henry Holland was one of the original Proprietors of the Institution. George Canning and J. H. Frere added their cynical comments in a satirical 'Prospectus for the Royal Institution', George Canning and his Friends, ed. by Capt. J. Bagot (New York 1909), I, p. 162-164.

(40) The failure of this experiment perturbed Beddoes who tried to justify his claims respecting the medical properties of nitrous oxide in a letter published in Nicholson'sJournal, May I80oo, 75-76.

(41) Memoirs and Correspondence of Francis Horner M.P., ed. by Leonard Horner (Boston i853), I, p. I82.

(42) Jones, op. cit. (34), p. II2.

(43) Edinburgh Review, I, 450-460 (January 1803). The papers being reviewed were Young op. cit. (8) and (69). Brougham championed Davy whose attributes were 'unimpaired by the enervating influence of the Royal Institution'. Edinburgh Review, II, 390(January 1808).

(44) Paris, op. cit. (27), 104. Davies Giddy, later Gilbert (1767-1839), was Davy's friend and pat- ron. He was President of the Royal Society for three years following Davy's resignation in 1827.

(45) Notebook, I8/5v; Lectures, I, p. 53I-532. (46) Paris, op. cit. (27), p. 8I.

(47) There appears to be no extant record of the requests which Young made in this petition. (48) In the I82os he contributed a number of short notes to the QuarterlyJournal of Science which

was edited by William Brande at the Royal Institution. (49) Dr Young's Reply to the Animadversions of the Edinburgh Reviewers, &c. (London 1804). Re-

printed in Miscellaneous Works of the late Thomas Young, M.D., F.R.S., &c., ed. by G. Peacock (London 1855), I, p. 2I5.

(50) Ms. Add. 13 (Plate 2). References of the microfilm edition of these notebooks are given in terms of the notebook number followed by a solidus and then the frame number. Where a single page has been photographed, only the above information is given, but



III

where a double page occurs on the same frame, the left (v) or the right (r) side is speci- fied. Thus Notebook, I6/I2r refers to the right side of the I2th frame of notebook i6.

The notebooks bear the stamp 'London University' which suggests that they were

acquired by University College some time between 1828 and 1836 during which period it bore the name London University. I cannot at present throw any light on how the notebooks arrived at University College.

(51) Young may have lost the notes for these first two lectures because he wrote a brief outline of their substance on spare pages near the front of Notebook 17.

(52) Lectures, I, v.

(53) Op. cit. (I9). These articles contain some inaccuracies which do not appear in circulated

copies-for example, two articles bear the number 480. (54) For example, 'Proof by the Whirling Table', Notebook, 4/2r. (55) Peacock, op. cit. (2), p. I35.

(56) One example is Harrison's improvement to the clock's movement. Notebook, 11/8.

(57) Notebook, Io/5r; 7/2v. (58) The number of references which Young made to various philosophers in the first volume of

the Lectures gives some indication of his intellectual debts. The following are the seven authors to whom Young most frequently refers and the number of citations-Newton, 55; Hooke, 27; Huygens, 24; Laplace, 23; Herschel, 22; Euler, 18; Robison, i6.

(59) Notebook, 16/18. (60) Ibid., 9I/I2v.

(61) Outside his own research, one of the major additions he made to the Lectures concerned

Davy's investigations on galvanism and electrolysis. Lectures, I, 674-680. (62) Young's concepts of the ether will be more fully discussed in my paper 'The Changing

Role of Young's Ether', to be published in Bri. J. Hist. Sci.

(63) Op. cit. (7), 125-130. (64) Op. cit. (7) and (8). (65) In order to explain gravitation Young would have had to adopt the inverse distribution of

the ether so that it is rarer in dense bodies than in rare ones as Newton had supposed. (66) Syllabus, Art. 493; Notebook, 20/2r. (67) Young, 'Experiments and Calculations relative to Physical Optics', Phil. Trans., 94, 12

(1804). (68) Notebook, I6/I6v. (69) Young, 'An Account of some Cases of the Production of Colours not hitherto Described',

Phil. Trans., 92, 387-397 (I802). (70) Syllabus, Art. 374. (7I) Lectures, I, 443-444. (72) Op. cit. (8), 32-33. (73) Notebook, I6/I9r. (74) Op. cit. (69), 393-394. Read I July 1802.

(75) Lectures, I, 463. (76) Notebook, I6/I6r. (77) Lectures, I, 464. (78) Notebook, I3/3v. (79) Ibid., I6/i5V. (80) Ibid., I6/Isr.



TT2

81) Ibid., I6/2ov. I cannot positively identify the philosopher to whom Young referred in this

quotation but it was probably Wollaston.

(82) Young, 'An Essay on the Cohesion of Fluids', Phil. Trans., 95, 65-87 (I805). (83) Notebook, 19/9; Lectures, I, 6II.

(84) Syllabus, Art. 143; Notebook, 9/7. (85) Syllabus, Art. I48; Notebook, 9/Ior. (86) Lectures, I, 137; II, 46.

(87) Ibid., I, 152.

(88) Young contributed a short note on this subject to the meeting of the Royal Society held on 8 July I802. This note is recorded in the Journals of the Royal Institution, I, 194 (1802).

(89) Op. cit. (82).

(9o) Lectures, I, 618-630.

(9I) Op. cit. (82), 66.

(92) Ibid., 81-82.

(93) This diagram is based on Lectures, I, Fig. 530. The caption reads, 'The repulsive force of two particles of matter, situated at a distance AB or AC, is represented by the ordinates or perpendiculars BD, CE, drawn from the curve DE, supposing the force to be inversely as the distance; but the law of the force appears to be more nearly represented by a curve like FE. The line DFG shows the magnitude of the cohesive force, which overcomes the

repulsion at the distance AG, and is balanced by it when the particles arrive at the distance AB or AH. The dotted lines represent the nature of the changes made in the lines FE, DFG, and FH, by the elevation of the temperature.' He used these forces only in his discussion of cohesion. When a substance is in a gaseous state the particulate spacing is greater than AG and the particles repel one another. The only stable position on line DE is the point D which corresponds to a particulate spacing of AB. Presumably the substance is then either in a liquid or a solid state. On increasing the temperature the stable spacing becomes AK and the substance expands. These forces bear many similari- ties to those supposed by Boscovich to surround particles of matter. Young had dismissed Boscovich's model which he likened to 'the labyrinth of Daedalus' because 'the

grand scheme of the universe must surely amidst all the stupendous diversity of parts, preserve a more dignified simplicity of plan and of principles, than is compatible with these complicated suppositions'. Notebook, I9/I2v; Lectures, I, 6I5.



thomas young's lectures at the royal institution

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