348 Scientific Intelligence. 



repelled each other by the presence of heated bodies and were 

 attracted together by cold bodies. Interposing absorption media 

 gave no cine to the cause of the effect. — Proc. Hoy. Soc. (A), 

 Ixxix, pp. 285-295, 1907. j. t. 



6. Effect of a Magnetic Field on Ionized A ir in Movement. — 

 M. A. Blanc finds that a current of air having a velocity of 6 ni 

 y»er second passing through a magnetic field of 4000 Gauss units 

 is diverted by a force which is equivalent to that exercised by an 

 electric difference of potential equal to - 024 volts. He finds that 

 the velocity of the negative ions is greater than that of the posi- 

 tive ions in the ratio of 1 to 1*6. — Comptes Rendus, cxliv, pp. 

 739-741, 1907. j. t. 



7. Mechanical Working of Canal Rays. — A. A. Campbell 

 SwiNTON has constructed tubes similar to those employed by 

 Crookes to show the mechanical effects of the cathode rays. The 

 type employed was that of movable vanes. The author believes 

 that the effect observed was a true mechanical effect of the posi- 

 tive rays and not a radiometer effect. — Proc. Hoy. Soc, lxxix, 

 pp. 391-395, 1907. j. t. 



8. Velocity of Sound in Fluids. — It has often been suggested 

 that Kundt's dust figures afford an interesting method of study- 

 ing the velocity of sound in various media. Karl Dorsistg has 

 elaborated the method, using many interesting modifications of 

 Kundt's method. The powder employed was pulverized pumice 

 stone which was carefully dried in a furnace. It was found that 

 the velocity in water increased with rising temperature ; in other 

 fluids diminished under a similar condition. The ratio of specific 

 heats of ether at constant volume and pressure was cp / cv = 1'376. 

 — Ann. der Physik, No. 2, 1908, pp. 22 7-251. j. t. 



9. On Factors serving to Determine the Direction of Sound. — 

 In an interesting and apparently exhaustive study of this subject 

 Mr. T. J. Bowkler concludes "that in noting the direction of a 

 fog horn at sea the observer should be well away from any reflect- 

 ing surface of any kind. (In one experiment an umbrella held to 

 one side of the head at a distance of two feet displaced the sound 

 image 20°.) It adds to accuracy in fixing the direction to 

 have a flat board slung on the shoulders vertical and parallel to 

 the axis of the ears. This increases the intensity in front and 

 shuts off sound from the rear. I think it would also be better to 

 have two short blasts of three seconds each, every half minute 

 at sea, rather than a long blast every minute. Fog horns should 

 be placed well above any reflecting surface, but it might add to 

 their carrying power if a large disk or sounding board were placed 

 horizontally directly over them." — Phil. Mag., March, 1908, 

 pp. 318-332. j. T. 



