Chemistry and Physics. 405 



adapted to the analysis of borotungstates. Precise details of 

 the method of operation are given, together with numerous test- 

 analyses which show remarkably good results. — Bulletin, IV, v, 

 217. h. l. w. 



5. Canal Rays. — J. Stark and W. Steubing continue the 

 studies of J. Stark upon the Doppler effect in these rays, with 

 apparatus affording a large dispersion (a Rowland plane grating 

 with a ruled surface of 8Xh) cm and 15,000 lines to the inch). 

 The observations are given in full tables, which give the fall of 

 potential of the dark space and velocity of rays. The fall of 

 potential at the cathode varied from 390 volts to 9600 ; the veloc- 

 ity of the canal rays varied over this range from 1*299*10 7 to 

 1*760*1 7 . Much space is given to the discussion of the cause 

 of the variation observed in the Doppler effect, especially the 

 maxima and minima. The article closes with a discussion of the 

 observed reflected canal rays, which give a Doppler effect, with a 

 cathode fall of 2500 volts. The reflection of the positive charge 

 of the canal rays amounts to 50 per cent. — Ann. der Physik, No. 



pp. 974-998. j. t. 



6. Zeeman Effect of Mercury Lines. — P. Gmelin has studied 

 this effect with the lines of rare lengths 5790, 5789, 4916, 4358, 

 and shows how the strength of a magnetic field can be measured 

 by a determination of the Zeeman effect. The article closes with 

 the following table : 



e 



Classen (cathode rays) — = 1*776 X10 7 



Bacherer (Becquerel rays) — l*730x!0 7 



Gmelin (Zeeman effect) -= 1*771 X10 7 . 



— Ann. der Physik, No. 5, 1909. j. t. 



7. Presence of Rays of High Penetrability in the Atmosphere. — 

 The extension of our knowledge of radio-activity has led to much 

 study of the presence of y-rays in the earth and in the earth's 

 atmosphere. Th. Wulf describes an improved and portable 

 electrometer which is well adapted for the study of radio-activity 

 and he applies it to a study of the y-rays in the atmosphere, 

 finding a winter type without the midday depression which char- 

 acterizes the summer type. — Physik. Zeitschrift, No. 5, March 1, 

 1909, pp. 152-157. j. t. 



8. Use of Radiometer for Observing Small Pressures. — J. 

 Dessar states that if the residual gas in a radiometer is helium, 

 pulverized carbon cooled by hydrogen is incapable of lowering 

 the pressure so that the vanes will not turn, when the light of the 

 voltaic arc is concentrated upon them. On the contrary, when 

 the residual gas is hydrogen the absorption of the gas by the 

 carbon is sufficient to cause all movement to cease. He believes 

 that a radiometer filled with helium will prove a useful apparatus 

 for the study of radio-activity. — Proc. Roy. Soc, London, Series 

 A, vol. lxxix, 1907. j. t. 



