Rug., t887.] ~ciotli~c Notes a,zd Comments. 159

F2,5oo are borne by the director. Considerable interest at taches to this new ~nterprise, from the fact that it is now not only probably the best equipped meteorological observatory on this Continent, but because the observat ions ,are, as they should be, made for the most part with automatically recording instruments, with occasional checking by direct eye readings, If the science of meteoro ogv is ever successfnlly to refute the charge of publ ishing torae upon tome of disconnected and aimless observations, it must be th rough observatories that flirnish conlz:nz~ous records of aff the weather factors, Although the scope of Mr. Rotch ' s observatory is wider in this respect than that of any American institution we know of, it is hoped this is but a beg inn ing in an attempt to automatically record and observe every known factor. I t is gratifying to note the character of the equipment. It consists of a s t andard barometer by Hicks, compareda t Kew, and one by Green ; a Draper self-record- ing mercurial barometer and an aneroid ba rograph by the Richard Brothers, Paris: thermometric s tandards by Hicks and by Baudin, with working stand- ards by H. J. Green, a R ichard ' s thermograph ; a Koppe hair hygrometer , wet and dry bulb thermometers ; a Draper recording anemoscope, a D r a p e r recording anemometer, a Rob inson anemometer , with the Gibbon self-register ; a Rotch wind-pressure gauge ; Rotch self-recording rain and snow gauges ; the Cmnbdl-Stokes sunshine recorder, a Jordan sunshine recorder ; a cloud mhror for the measurement of the azimuth and altitude of clouds, and other instruments. The results are pr inted in neat t abular form, and are accom- panied by tracings from the self-recording instruments, to illustrate certain meteorological p h e n o m e n a . M . B . S .

ON THF SCINTILLATION OF STARS.--K. Exner (As/ton. 2Vac~., 1 1 6 , To6), in view of the present problem of de termining places where large instru- ments would suffer least from a tmospher ic disturbances, draws a t tent ion to • the necessity of there studying the scintillation of stars. It is well known that the larger the apertnre of the instrument , the less unsteadiness is noticed in fixed stars, and this, as Newton long since remarked , arises from the fact tha t the image is an integration of number l e s s rapidly vibrat ing independen t rays and, is consequently, larger and as a whole relatively quiescent. To show the independent movements , there was placed before the twelve-inch refractor of the Vienna Observatory a cap with three small opening s lying in a straight line. On directing to Sirius a n d pushing in the ocular, the th ree round images of the star appeared in continual relative motion. Observat ion. by means of an ins t rument of large aperture, therefore shows the stars as quiescent discs, or as circles of dispersion due to scintillation (Scintilfations- zerstreuungs2,reise) whose radii equal the ampli tude of vibration, which the star would show with reduced aperture. Authorities are cited to show the numerical value of this ampli tude, Holetschek f inding it 5 z~ to 7zt'5, Struve, 4~r; Carlini oscillations of Io H to 12 ~z, while Dr. Exner, by sc in t i l lometer observations, determined the ampli tude a t 6 '/. Scintillation is far greater by day than by night ; Mont igny measur ing its ampl i tude by day as great

The advantage of scintil lometer observat ions is considered by the au thor

16o £'cienliJic Notes and Comments . [ J . F. I . ,

the more evident, since measurements have never yet been made to determine the relation between the grade of scintillation and the elevation of the place of observation, and because he is convinced, from unpublL-hed observations, that scintillation of the stars arises principally in the lower s t ra ta of the atmosphere. M . B . S .

A~_'~losI'~ll,.'l'dC ELrCTPdC)T;'.--R. Nohrwold( 14/ied. Ann., 1¢1, 448), from a long series of experiments, draws some interesting conclusions as to the pos- sibility of electrifying air. By coating a suitable glass receiver on the inside with glycerine, and then filling it with smoke, he is able to show to a consid- erable audience that one or two turns of a T6pler machine discharged from a point within the receiver, is sufficient to clear the air by projecting the smoke upon the glycerine. Following up the question of statically electrifying pure air by a great variety of tests, he concludes that he has shown more thor- oughly than has been done heretofore, that electricity, s t reaming out f rom points, cannot statically electrify the air itself, but ra ther the suspended dust consisting of solid or liquid bodies. Glowing plat inum wire was found to render pure air capable of being electrified, on account of the slow evapora- tion or emission of small particles, and it was shown that on these particles, and not in the air, the charge resided. He concludes tha t it is very probable that atmospheric air and other gases probably conduct themselves s imilar ly-- cannot be statically electrified. He also gives a new experiment, according to which, at ordinary tenIperatures, negat ive electricity of high potential more readily escapes from solid conductors into a tmospheric air, than positive electricity. M . B . S .

FINE THF.I';ADS OF (.~UAR'rz.~C. V. Boys (Phil. ~ag . , 2 3 , 489), gives a n account of some very interesting experiments in the product ion of the finest threads of glass and other materials, with their properties and some sug- gested uses. The most remarkable threads he has found are those of quartz. Of these, he says : " A s torsion threads, these fibres of quartz would seem to be more perfect in their elasticity than any known ; they are as strong as steel, and can be made of any reasonable length, perfectly uniform in dia- meter, and, as already explained, exceedingly fine (i. e., ' beyond the power of any possible microscope '). The tail ends of those that become invisible must have a moment of torsion xoo,ooo,ooo times less than ordinary spun glass ; and, though it is impossible to manipula te with those, there is no dif- ficulty with threads less than one- ten- thousandth of an inch in diameter ." The drawing is neatly accomplished by using a small cross bow and very light arrow. One end of the glass is a t tached to the arrow, while the inertia of even a very small mass is sufficient to prevent the other end from following. Since these fibres can, by this method, be made finer than any cobweb, a n d also, in the case of quartz, possess the remarkab le elasticity indicated, a. variety of interesting applications may be expected. M . B . S .