Chemistry and Physics. 327 



lines. The authors indicate that the varying results of different 

 observers result from the use of different methods of observa- 

 tion rather than from the deficiencies of the apparatus. — Ann. der 

 Physik, No. 3, 1903, pp. 457-4 78. J. t. 



9. Electricity carried by a Gaseous Ion. — Prof. J. J. Thomson 

 has repeated his determination of this quantity by means of 

 radium and more accurate apparatus. The number 3-4X10 -10 

 was found as the charge in electrostatic units of the gaseous ion. 

 This is about half the number 6 -5 X 1 0~ 10 found in the author's previ- 

 ous experiments. The author attributes the difference to the 

 failure of the first experiments to catch the positive atoms, thus 

 making the value of n, the number of ions per c.c, little more 

 than half the true value, Avhile it made the value of e, the charge 

 in electrostatic measure on an ion, twice as great as it ought to 

 have been. — Phil. Mag., March, 1903, pp. 346-365. j. t. 



10. Potential Distribution in the dark Cathode Space. — A. 

 Wehxelt finds that there are no potential maxima or minima in 

 this space. The results, therefore, of W. P. Graham arise from 

 faults of method of investigation. The author finds that Prof. 

 Shuster's interpolation formula representing the run of potential 

 is not confirmed by his investigation. — Ann. der Physik, No. 3, 

 1903, pp. 542-580. j. T. 



11. Mechanics, Molecular Physics and Heat ; by R. A. Milli- 

 kan. 242 pp. (Chicago : Scott, Foresman and Co.) — This is a 

 treatise adapted to a twelve weeks' college course, in which the 

 author has endeavored to combine a class-room text and labora- 

 tory manual. A certain number of well chosen laboratory exer- 

 cises are made the basis of the course, whose object is to teach 

 thoroughly a few fundamental principles rather than to present 

 a large mass of facts. The theoretical discussions are generally 

 sharp and clear and are followed by directions for the laboratory 

 exercises, with illustrative problems. Another volume, for the 

 second third of the year, covering the subjects of Electricity, 

 Light and Sound, is to follow. This plan necessitates, for the 

 third part of the year, a course of demonstration lectures on such 

 parts of the subject as are more suitable to lecture than to labora- 

 tory presentation. d. a. k. 



12. American Physical Society. — The American Physical Soci- 

 ety is now joined with the Institution of Electrical Engineers 

 and the Physical Society of London in the direction of the pub- 

 lication of " Science Abstracts " (edited by G. W. de Tunzel- 

 mann, London), and has elected Professor E. H. Hall of Harvard 

 University as its representative on the publishing committee. In 

 consequence of this arrangement, "abstracts" dealing with physics 

 will in future be received by all members of the American Phys- 

 ical Society. 



13. The A B C of Photo-Micrography ; by W. H. Walms- ^ 

 ley, 155 pp., 29 photo-micrographs. New York : Tennant & 

 Ward. — Mr. Walmsley is a recognized authority in the photo- 

 micrographic world and his little manual is a welcome addition 



to the scientist's outfit. The subject is treated plainly yet thor- 

 oughly and comprehensively. 



