Intelligence and Miscellaneous Articles. 393 



bodies, with a view to determine if certain small specific 

 variations may not have escaped notice, owing to their not 

 having been searched for, on account of the bias of preconceived 

 ideas, and the lethargy produced by the influence of preformed 

 theories. Crystalline bodies of birefracting properties &c. 

 which, in relation to the luminiferous a3ther, are permeable to 

 light with different velocities in different directions, may spe- 

 cially suggest themselves for experiment. 



Since the successful pursuit of a research of this kind, 

 where specific differences of a very minute character are in 

 question, would no doubt entail considerable experimental 

 resources, with refined and delicate apparatus, which might 

 not be at the disposal of every one, the more therefore does it 

 become desirable to attract general attention to the subject. 

 The comparative dearth of discovery of any great physical 

 principle (of a fundamental character at least) within the last 

 few years would seem, if any thing, to call for additional zeal 

 in experimental enterprise. Although a negative result to the 

 investigations would not be decisive one way or the other in 

 regard to the validity of the explanation of gravity afforded 

 by the kinetic theory (for, of course, it is well conceivable 

 that such specific variations in gravific effect, if they exist, 

 might be too minute for detection with the appliances at our 

 command), yet a positive result would be so highly interesting 

 and important, that even a small prospect of success would 

 amply repay the labour of a careful trial, and enlist usefully 

 the skill and ingenuity of experimenters. 



Heatherfield, Bournemouth, 



LIY. Intelligence and Miscellaneous Articles. 



THE EFFECT OF GREAT COLD UPON MAGNETISM. 

 BY JOHN TROWBRIDGE. 

 A N investigation upon the magnetic condition of steel and upon 

 *V the magnetic permeability of iron is now in progress in the 

 Physical Laboratory of Harvard University. The preliminary ex- 

 periments are interesting, since they show that very low tempera- 

 tures exercise far greater influence on the magnetic condition than 

 has been noticed by previous observers. 



It is stated by Wiedemann* that the cooling below the tempe- 

 rature at which steel is magnetized enfeebles the magnetic condi- 

 tion. A bar which was maguetized at 6° C. or 8° C. gave at 4° C. 

 and —25° C. intensities represented by 5 # 08 and 4-90. This re- 

 presents a loss of less than 4 per cent. In my experiments the 

 magnetic bar magnetized at 20° C, when subjected to a tempera- 



* Daguin, Traite de Physique, nouv. ed., " Influence de la temperature 

 d'aimantation." 



Phil. Mag. S. 5. Vol. 11. No. 69. May 1881. 2F 



