504 Scientific Intelligence. 



in the relay circuit. He points out the effect of heat on the 

 coherer and shows that even the heat of the band can influence 

 its sensitiveness. The heat developed by the electric waves there- 

 fore under certain conditions may lead to an increased resistance 

 in the coherer. This development of heat might arise from a 

 definite potential-difference in the formation of stationary electric 

 waves. The author believes that we could gain more insight into 

 the more or less mysterious working of the coherer if we knew 

 more about the conditions of the conduction of electricity in metals. 

 Possibly electrolytic action analogous to that which takes place 

 in electrical discharges through gases in which the motion of ions 

 is involved may in time explain the phenomena of the coherer. — 

 Wiecl Ann., No. 10, 1898, pp. 284-307. j. t. 



10. Theory of the Hall effect in an Electrolyte. — Roiti, Journal 

 de Physique, 1883, failed to find any Hall effect in a liquid. 

 Recently Bagard (Comptes Rendus, vol. cxxii and vol. cxxiii, 

 1806) claims to have observed an effect. This is denied by 

 Florio (Nuovo Cimento [4], vol. iv, 1896). Dr. F. G. Donnan 

 calculates that in order to detect the effect a difference of potential 

 of the order of 10,000 volts and a very powerful magnetic field 

 would be necessary. — Phil. 3fag.,~Nov. 1898, pp. 465-472. j. t. 



Dr. Hall, in recent experiments in the Jefferson Physical Labo- 

 ratory, has failed to confirm Bagard results and points out 

 the disturbing effects of convection currents in the electrolyte 

 arising in a magnetic field. j. t. 



11. The Free Expansion of Gases. Memoirs by Gay-Lussac, 

 Joule and Joule and Thomson. Translated and edited by J. S. 

 Ames, Ph.D.; pp. 106. New York, 1898 (Harper & Brothers). 

 — The inauguration of the series of Harpers Scientific Memoirs 

 under the editorship of Professor J. S. Ames was announced in 

 our August number. The first volume of the Series has now 

 appeared and shows definitely the details of the plan. As before 

 stated, it is somewhat analogous to the Ostwald series of scientific 

 classics published in Germany. The single volume, however, is 

 not confined to a paper by one author, but a series on a given 

 subject are brought together. For example, the present volume, 

 on the Free Expansion of Gases, opens with Gay-Lussac's memoir 

 of 1806; an early paper by Joule (1845) follows, and then subse- 

 quent papers by Thomson and Joule (1853-1862). This bringing 

 together of a number of memoirs on a given subject is an admir- 

 able plan, and serves to give a considerable degree of complete- 

 ness to the discussion of the topic in question. 



Further, the editor has added a brief biographical sketch of the 

 authors included, with a statement of their most important sci- 

 entific researches ; also at the close, a list of books of reference 

 and of other articles dealing with the same topics, and finally an 

 index. 



The titles are now announced of the subjects which are to be 

 covered by nine other volumes of the Series; thus volume II 

 includes Fraunhofer's Papers on Prismatic and Diffraction Spec- 



