608 SCIENTIFIC RECORD FOR 1883. 



induced in it by covering it with a tube of iron. (J. Phys., .April, 1883, 

 II, n, 192.) 



Meyer has given his results upon the magnetic permeability of the 

 magnetic metals obtained with weak magnetizing forces. A cylinder 

 of the metal was made the core of an earth inductor, the earth's field 

 being used. He concludes, (1) the magnetizing function has a positive 

 value for a diminishing magnetizing force; (2) it increases at first with 

 the magnetizing force; and (3) it increases for weak magnetizing forces 

 with the temperature. The value 2.24 for pure nickel, with a magne- 

 tizing force 3.096 was obtained. (Am. J. ScL, April, 1833, III, xxv, 

 309.) 



In a paper read at the meeting of the British Association, Ewing has 

 given the results of an extended investigation of magnetic suscepti- 

 bility and retentiveness in iron and steel. He finds that soft iron 

 retains 90, and even 93 per cent, of the induced magnetism, after the 

 magnetizing force is removed. Pieces of soft iron held an amount of 

 magnetism per unit of volume greatly exceeding that retained by the 

 best-tempered steel. But the condition is highly unstable, the slightest 

 mechanical disturbance, such as gentle tapping, removed the residual 

 magnetism completely. (Nature, October, 1883, xxvrn, 625.) 



Borgman has succeeded in establishing the fact that iron is heated 

 by being rapidly magnetized and demagnetized. Similar tubes of iron 

 and of copper were placed in reservoirs of glass which served as the 

 bulbs of air thermometers. The magnetizing currents surrounded these 

 reservoirs and were reversed from five to twenty times a second. No 

 heating of the copper was observed. (Soc. Phys. Chim. Busse, xrv, 67 ; 

 J. Phys., December, 1883, II, n, 574.) 



Wassmuth has calculated, from the fact observed by Stefan in 1874, 

 that the specific heat of iron is greater when it is magnetized than in 

 its natural state, what the temperature should be in order that the 

 magnetic moment may be zero. He finds, for the difference of the two 

 specific heats, 2.7 xl0~*, and for the temperature, 1,346°. (Ber. Ale. 

 Wien, 1882, 112 ; J. Phys., April, 1883, II, n, 194.) 



Himstedt has studied the damping effect exerted by a plate of iron 

 upon a magnetic needle vibrating above it. Comparing the results with 

 those given by copper plates of the same dimensions, he finds that 

 while for copper plates the logarithmic decrement of the oscillations 

 is proportional to the duration of the oscillation, for iron plates the log- 

 arithmic decrement is independent of this duration. From this it fol- 

 lows that the damping effect due to ordinary induction currents is only 

 a very small fraction of the total damping effect which was observed. 

 (J. Phys., March, 1883, II, n, 135.) 



Barrett has described some experiments made under the direction of 

 a committee of the Society for Psychical Research, to test the accuracy 

 of Reichenbach's assertion that the magnetic field is luminous to cer- 

 tain persons. Two persons were subjected to the most careful tests, 



