of observed phenomena and its translation into applicable design data. Visual corona, its occurrence under a variety of conditions and its characteristics are examined at length. Under the caption “spark-over” the initial complete breakdown of a gaseous dielectric is given an equally lengthy analysis. In logical order come the consideration of the losses due to corona, corona and spark-over in oil and liquid insulators, and an examination of numerous solid insulations. In a thorough chapter on lightning the recent work of some of the most notable contributors in that field has been utilized. In general the work is well documented by numerous references to original sources. A final chapter, a reduction to practice, deals with the design of apparatus where solid liquid and gaseous insulations enter in combination. An extensive collection of tabu- lated data is given in an appendix. Illustrations are of a high order of excellence and numerous. The work is indeed a fine piece of book-making which reflects credit alike to author and publisher.

L. E. I’.

METALLURGY OF WHITE METAL SCRAP AND RESIDUES. By Edmund Richard Thews, consulting metallurgist. 383 pages, illustrations, 8vo. New York, D. Van Nostrand Company, Inc., 1930. Price, $5.50. “Scrap” is a characteristic word of our present day. Everywhere we find

scrap; scrap paper, scrap wood, scrap metal, scrap automobiles and in some of our largest cities a very considerable collection of scrap houses. A good deal of attention has been paid to devising methods for utilizing some of these forms of scrap. Paper scrap, for example, is a very abundant and troublesome item in the management of our city streets. Unfortunately the great bulk of paper material is of such inferior character that it does not pay to recover it even under the cheapest methods.

The book in hand is devoted to the chemistry and metallurgy of a very important class of scrap, that from some of the metals which are extensively used in our household life and which are being abandoned in consequence of injury during use. Tin, lead and zinc are among the most important, but aluminum is rapidly becoming familiar in scrap form. Notwithstanding the attention that has been given to this subject it appears that no comprehensive description of the methods for treating these materials has been furnished to American literature, and the present volume is offered to fill this want. A small handbook on the subject was published in England about ten years ago and the author contributed an essay in German lately.

In the preparation of the volume the author has given, not only the important facts directly related to the treatment of white metal wastes, but also the ele- mentary principles of such procedures. Aluminum has been included in the work and attention has been paid to the requirements of small and medium size plants, conducted independently as well as to the operations of large works which carry on for themselves methods for recovery. Many points accessory to the operations have been included. As the first publication in book form in United States upon the subject, it will be a welcome addition to the library of the works-chemist and the metallurgist. The author invites suggestions from users of the book and it is to be hoped that he will receive such aid, for while it is a comprehensive volume, representing a large amount of experience and labor, there may be

Mar.. 1930.1

further data in possession of those engaged in such operations. The work is liberally illustrated, printed clearly on good paper, and represents another gratifying evidence of the advance in applied chemistry in this country.

U T

MOI)EKX METHODS OF Coc0.1 AND CHOCOL~ITE M~JFACTCRE. By H. I\‘.

Bywaters, D.&z., Ph.D., A.R.C.Sc. and F.I.C. 316 pages, illustrations, 8vo. Philadelphia, P. Blakiston’s Son 2% Company, Inc., 1930. Price, $6.00. South America has given to the world a considerable number of products that

make for human safety and comfort. From that half-continent of which the general aspect could be described as Bishop Heber describes Ceylon, we get chocolate, Peruvian bark, potato (sweet and white), tomato and coca leaves. Many other things might be mentioned. Of the four vegetable products, cacao, coffee, tea and mat&, which contribute so largely to human enjoyment in the “cups that cheer but not inebriate,” cacao is the only one that finds extensive employment in other fields than as a beverage. In the form of chocolate and also under the erroneous but usual name of cocoa, it administers to the “sweet tooth” of the nations. In the book before us we have a comprehensive account of the various forms of cacao as cultivated and gathered in different parts of the tropical world. The amount of material now produced is enormous. The importation into the United States alone amounts annually to several hundred thousand tons. With such a demand it follows that cultivation has been carried on on a large scale in many places where climate permits the satisfactory growth of the plant. The usual interference by various diseases, fungous and by the action the insects have, of course, developed remarkably and have been antagonized more or less successfully by research. A brief historical notice is given from which we learn that it was not until 1519 that the cacao tree was seen by Europeans on Cortez’ expedition to hIexico. The word cacao is a modification of the native name adopted by the Spaniards. A preliminary section of about sixty pages gives an account of the growth of the bean, its structure, the varieties from different places, also methods of storage and the means of determining quality. In any great industry of this type other industries will be influenced for better or worse. The author points out that an enormous production of chocolate stimulates the sugar industry. The second section of nearly one hundred pages covers all the details of the manufacture of cocoa, by which term it is now generally agreed among manufacturers to indicate the powder, chocolate being the refined mixture of this with sugar with or without the cacao butter. It is important, by the way, to avoid the confusion between the chocolate-nut which is one name for the product here under consideration and the coconut which has often been confused with the chocolate nut on account of the incorrect spelling cocoanut. The products are entirely different. The chocolate-nut or cacao is derived from Theobroma cacao, the coconut from Cocos nucifera. Linnaeus probably found chocolate exceedingly pleasant and he dubbed the plant yielding it as Theobroma “food for the Gods.” The coconut, the fruit of a palm, has no botanical or chemical analogy to the chocolate-nut. Cacao contains a well- marked nitrogenous principle closely analogous to caffein which occurs in coffee, tea and mat&. It does not appear that we as yet know ver>- much about the effects of these substances upon the human system but there is a good deal of