384 Scientific Intelligence. 



benefit of those who may be unfamiliar with the work, it may be 

 added that it is a theoretical treatment of the subject, with many 

 references to practical applications. h. l. w. 



7. Exercises in Chemistry ; by W. McPherson and W. E. 

 Henderson. 12mo, pp. 69. New York, 1906 (The G-inn Com- 

 pany). — This little book comprises directions for 49 laboratory 

 exercises in elementary chemistry. It is designed to be used in 

 conjunction with the authors' text-book, "An Elementary Study 

 of Chemistry." The experiments are well chosen for simplicity 

 and for imparting knowledge of the subject, while the directions 

 are clear and the illustrations showing the arrangements of appa- 

 ratus are excellent. The book appears to be an excellent one for 

 the use of younger students. h. l. w. 



8. Specific Charge and Velocity of Cathode Rays excited by 

 Rontgen Rays. — A. Bestelmeyer employs in his investigation 

 a magnetic field with lines of force at right angles to the lines 

 of force of an electric field so arranged that they exercise oppo- 

 site effects upon the moving electrons. He concludes that : 



(1) The velocit}^ of the excited cathode rays is independent of 

 the intensity of the exciting Rontgen rays and increases with 

 the hardness of the. latter rays. 



(2) The value of -— = 1*72 x 10 r obtained is much smaller than 



Simon's number. 



(3) This value changes with the velocity. 



(4) Although this value is nearer Lorentz's value than those of 

 Abraham and Bucherer, the conditions are not sufficiently exact 

 to form a conclusion. 



(5) The method of crossed magnetic and electric fields is much 

 to be preferred to the method of parallel fields. — Ann. der Physik., 

 No. 3, pp. 429-447. J. t. 



9. Wave Length of Rontgen Rays. — J. D. Van der Waals, Jr. 

 points out that the value of wave length obtained by various 

 observers, notably Haga and Wind, Sommerfeld and Wien, 

 depends upon the manner of impact of the electrons. Wien had 

 assumed that the cathode ray particles gave up their great veloc- 

 ity to the anticathode in a straight line impact. If, however, there 

 is a scattering effect, collisions not in a straight line, zigzag effects, 

 another value of wave length might be anticipated. — Ann. der 

 Physik., No. 3, p. 603, 1907. J. t. 



10. Chemical- Effects of the Electric Discharge in Rarified 

 Hydrogen and Oxygen. — Rev. P. J. Ktrby calls attention to a 

 previous paper by him, Phil. Mag., Jan. 1905, which showed 

 that the chemical effects were most intense within the region of 

 the cathode fall of potential. He has taken up the subject with 

 modified apparatus and has confirmed his previous results. He 

 estimates that 5XlO~ 12 ergs is the superior limit of the work 

 involved in separating the atoms of oxygen. Very little ozone 

 is formed during the discharge in rarified oxygen. The quanti- 



