280 Scientific Intelligence. 



ties in Pennsylvania were largely connected with philosophical 

 and religious work, but nevertheless he did a considerable amount 

 of laboratory work and wrote frequently in favor of the phlogis- 

 tic theory, to which, as is well known, he adhered to the end of his 

 life, although his own discovery of oxygen had paved the way 

 long before for the modern views of oxidation. The book pre- 

 sents the subject very well, and is to be recommended to those who 

 are interested in the history of chemistry. It mentions some 

 important incidents, such as the acquaintance of Priestley with 

 George Washington, and an invitation to him by the latter to visit 

 his home at Mount Vernon. h. l. w. 



4. Introduction to General Chemistry; by H. Copaux. 

 Translated by Henry Leffmann. 12mo, pp. 195. Philadel- 

 phia, 1920 (P. Blakiston's Son & Co.). — This is a clear and con- 

 cise exposition of the principles of modern chemistry as recognized 

 today by the leaders of the science. It should be a valuable guide 

 to those who wish to obtain a clear view of the subject. Besides 

 presenting the older fundamental laws and theories of chemistry, 

 the book discusses the more modern topics, such as radioactivity, 

 the structure of the atom, the phase rule, etc. A short appendix, 

 dealing with hydrogen-ion concentration, has been contributed 

 by the translator. h. l. w. 



5. A Text-Book of Organic Chemistry; by E. DeBarry Bar- 

 NETT. 8vo, pp. 380. Philadelphia, 1920 (P. Blakiston's Son 

 and Co.). — In this text -book from England the author has 

 described the important classes of compounds both aliphatic and 

 aromatic. He has generalized, however, wherever possible and 

 has thus avoided the introduction of much specific descriptive 

 detail, which is always troublesome to the beginner. General 

 theories have been grouped under one heading in order that tliory 

 may be more readily referred to when occasion requires. Several 

 pages have been devoted to a description of the original literature 

 and its use. This is indeed worthy of mention since the use of 

 the journals is an essential part of every organic chemist's train- 

 ing and attention should be paid as soon as possible to this phase 

 of the student's work. The book gives a very favorable impres- 

 sion, but unfortunately many errors in typing have escaped the 

 notice of the proof readers. j. j. donleavy. 



6. Comparison hetween wave lengths of solar and of terres- 

 trial origin. — The relati\dty theory of Einstein offers a prediction 

 that the wave length of light emitted by an element upon the sun 

 should be about two parts in a million longer than that of the 

 same element upon the earth. Such indications of a difference as 

 have hitherto been published have not been accepted as altogether 

 valid. A recent determination by A. Perot justifies the existence 

 of a real difference. His investigation was made upon the sec- 

 ond head of the cyanogen band, 4216, which is particularly favor- 

 able for observation on account of its isolation in the solar spec- 

 trum. Its wave length was taken as 4197 A, and the measure- 

 ments made by a spectroscopic interferometer. 



