490 SCIENTIFIC RECORD FOR IBS'! 



stantsin absolute measure, by the method of oscillations, the magnetiz- 

 ing forces being from 300 to 2,500 Gaussian units. For a solution of fer- 

 ric chloride of density 1.40, K. 10^ = 35. The constants of diamagnetic 

 liquid,s diminish when the magnetizing force increases; in gases the 

 reverse is true. Oxygen charged with ozone is two or three times more 

 magnetic than pure oxygen. For a mi)gnetizing force of 1,308, the fol- 

 lowing values were obtained for K. 10'': water, — 0.453; alcohol, — 0.41G; 

 carbon disulphide, — 0.200; oxygen, + 0,059 ; oxygen ozonized, + 0.181. 

 {J. Phys., April, II, i, p. 201.) 



Berson has made a study of the effect of temperature on the magnetic 

 properties of metals by com])aring the magnetic moments of different 

 bars at different temperatures, when placed in a magnetic tield of uni- 

 form intensity. With iron the total and temporary raagnetizistions 

 both increase up to 260"^, above which the latter falls off rapidly, the 

 former slowly. In steel, the maximum of total mag'netization is obtained 

 at 260° also, but the permanent magnetization reaches its highest value 

 at 240°. A steel bar magnetized cold loses magnetism on heating, whi.e 

 one magnetized hot loses it on cooling. With nickel the total magnet- 

 ization increases up to 240° and diminishes so rapidly above 280° as 

 to be at 330°. If magnetized at 280°, the magnetic moment first in- 

 creases on cooling and then diminishes slightly; though it still remains 

 greater than at the temperature of magnetization. {Xatnre, December, 

 XXVII, p. 183.) 



The elongation of a bar of iron when magnetized was determined 

 by Joule in 1847 at l-200000th of its length, and by Mayer in 1873 at 

 l-277000th. Hard steel was noticed by both observers to contract when 

 magnetized. Barrett has now extended these investigations to cobalt 

 and nickel, and finds that in his apparatus iron elongates l-2G0000rh, 

 and cobalt l-425000th, while nickel contracts l-130C00th, the contraction 

 being instantaneous. On heating the bar to 50°, the retraction is only 

 three-fourths of its former value. {Nature, October, xxvi, p. 585.) 



Gray has called attention to the converse of these results of Barrett's, 

 obtained in some experiments made by his brother and himself under 

 Sir William Thomson's direction. Barrett finds that the effect of lon- 

 gitudinally magnetizing a bar of iron is to increase its dimensions lon- 

 gitudinally and to diminish them laterally, so that the volume remains 

 constant; while Thomson shows that the effect of increasing longitudi- 

 nal dimensions in an iron baris toinci-ease, and of increasing transverse 

 dimensions to diminish its longitudinal magnetization. {Nature, Octo- 

 ber, XXVI, p. G35.) 



Cheesman has investigated, under Kohlrausch's direction, the effect 

 of mechanical hardening upon the magnetic properties of steel and iron, 

 the results of which are in entire accordance with those obtained by 

 Euths and others with magnets hardened by heat. {Am. J. Sci., Sep- 

 tember, 111, XXIV, p. 180.) 



Clemaudot, in a communication to the French Academy, maintains 



