318 Scientific Intelligence. 



8. 'Velocity of Sound in Air and in different Vapors with 

 Ordinary and High Temperatures. — This is a very complete 

 study of the subject by E. H. Stevens. He employed the appa- 

 ratus described by Quincke in Wied. Ann., lxiii, p. 66, 1898, 

 which he found to be the most accurate for the purpose that has 

 been devised. In general it consists of two cylinders. The 

 wider, called the interference cylinder, is closed at one end and 

 holds the gas or vapor. In the neighborhood of the mouth of 

 the tube is the resonator of a tuning fork. The wave, spreading 

 out from this, passes into the tube, and is reflected from the 

 closed end, forming with the direct wave a standing wave. The 

 wide cylinder contains also a much narrower tube, open at both 

 ends. The end projecting from the wider tube is provided with 

 a rubber attachment which one applies to one ear, while the other 

 is suitably closed. One pushes this narrow tube to and fro in the 

 wide cylinder until one finds maxima and minima. The author 

 gives the following table of the velocity of sound and the ratio 

 of specific heats at constant volume and constant pressure. 



Substance. t°. Vm/sec. k. 



Dry air 0° 331-32 1*4006 



" 100 386-5 1-3993 



" 950 686-0 1-34 



Ether ._ 99-7 212-6 1-112 



Methyl alcohol 99*7 350-3 1-256 



Ether alcohol 99*8 272-8 1*134 



Bisulphide carbon .. . 99*7 223-2 1*234 



Benzol 99*7 205*0 1*105 



Chloroform. __ 99*8 171*4 1*150 



Acetic acid _._ 136*5 '_■_., 1-147 



Iodine 185-5 140'0 1*303 



— Ann. der Physik, No. 2, 1902, pp. 285-320. j. t. 



9. Chemical Action of Cathode Bays. — G. C. Schmidt con- 

 troverts the hypothesis of Goldstein (Wied. Ann., ii, p. 832, 

 1880) that the chemical action of the cathode rays is due to a 

 very thin layer of ultra-violet light at the surface where the 

 cathode rays strike the substance. Schmidt finds that the 

 cathode rays are strongly reducing in their action, and work not 

 by the production of ultra-violet light, but in such a way that 

 the negatively charged electrons reduce the positive valency 

 charges of the metal. The last can then no longer hold back the 

 whole acid radical — it weakens it, in case it is unstable. With 

 salts of which the acid radicals are not unstable there enters 

 under the influence of the cathode rays a dissociation into ions ; 

 after a longer working eventually a small reduction. — Ann. der 

 Physik, No. 2, 1902, pp. 321-332. J. t. 



10. Effects of Currents of High Frequency upon the Human 

 Body. — It is often stated that high-frequency currents can be 

 received with comparative safety. H. Andriessen points out 

 that the strength of current is not considered in this general 



