4:00 Notices respecting JSeio Books. 



The Emission of Electricity from Hot Bodies. By Prof. 0. W. 

 Eichakdsoj*, E.R.S. Second Edition; pp. viii-r- 320. (Mono- 

 graphs on Physics Series. London : Longmans, Green & Co., 

 1921.) Price 16s.net. 



The second edition of Prof. Richardson's book has been brought 

 up to date, in the subjects with which it deals, by the extension of 

 certain- sections and the rewriting of others. There is now 

 included an account of von Laue's treatment of the problem of 

 the equilibrium of electron atmospheres in cases in which the 

 volume density effects are not negligible ; fuller explanation is 

 given of the deviation, at low voltage, from the three-halves 

 power law of thermionic current. Noteworthy also is the 

 description of the author's recent experiments on the emission of 

 electrons under the influence of chemical action. 



No reference is made to the application of the thermionic 

 current to the rectification and amplification of alternating 

 currents, a short account of which would surely have been of 

 value, if only to help students to realize how purely scientific 

 researches in this subject have made possible the recent strides in 

 the development of radio-telegraphy and radio-telephony ; again, 

 many properties of thermionic emission, such as the cooling effect, 

 are now being studied by means of the triodes used in radio 

 telegraphy. 



The book remains a store-house of ideas for those who are 

 seeking problems for research, especially in the chapters con- 

 cerning the emission of positive ions, the emission of ions by 

 heated salts, and ionization and chemical action, subjects which as 

 yet are only in the early stages of development. 



Bibliotheca Chemico-MaiJiematica : Catalogue of works in many 

 tongues on Exact and Applied Science, compiled and annotated 

 by H. Z. and H. 0. S. Two volumes, pp. 964. London : 

 Henry Sotheran & Co. 1921. 



This unique work consists primarily of a list of many books on 

 .pure and applied science, including mathematics. It w T as begun in 

 1906, and was expected to reach about three hundred pages. 

 It developed, however, in the hands of the compilers gradually 

 from a catalogue in the ordinary sense into a storehouse of 

 information about almost all the great works on science. It is 

 indeed a fascinating work, for there are many biographical and 

 historical references both in the descriptions of the various books 

 and in the notes which are appended to many of the entries. 

 The illustrations are exceedingly delightful. They have all been 

 obtained from the actual books by a photographic process, and 

 include, besides facsimiles of illustrations and portraits, textual 

 passages from works of historical importance, many of them 

 produced for the first time. We notice specially an illustration 

 from Boyle's New Experiments Physico-Mechanieal (1660), 

 showing his air-pump ; and portraits of Torricelli (1715), John 

 Napier (1616), and Thomas Young (1855). 



