of hoi Iron bcl-.ccen the idi/'le and blood-red Heat. 345 



tions have been repeated by many other authors, each sup- 

 posing that his results were at variance with the other. 



M.'Cavallo seems to have been the first writer, who was 

 fully aware that these contradictory statements arose from the 

 observations being made with the iron at different degrees of 

 heat. He found, that although iron at the red heat had a 

 greater power over the magnet than when cold, yet, at the 

 white heat, it had a less ; but he says he is still unable to de- 

 cide, whether all the magnetic power is intirely lost at the 

 white heat. (Cavallo on Magnetism, p. 312). More recent 

 experiments on this subject are also recorded in vol. ix- 

 Part I. of die Transactions of the Royal Society of Edinburgh, 

 by William Scoresby, Esq. But even here it does not appear 

 that this gentleman was aware of the total loss of poAver at a 

 certain temperature : for he observes (after showmg that iron 

 red hot lias a greater power than when cold) ; " The contrary 

 to diis has, I think, been generally asserted ; " from which it 

 would seem, that he had not heated his iron to a sufficient de- 

 gree to detect the non-action at the white heat. 



Notwithstanding, therefore, all the experiments that have 

 been made, it is pretty evident from the above remarks, that 

 considerable uncertainty still hangs over the results ; arising, 

 widiout doubt, from tlie v.ant of proper conveniences for heat- 

 ing bars of suificient size, and to a proper degree of intensity; 

 whereby one audior has noticed one fact, and another a difte- 

 rent one, without being aware how much depended upon a 

 very slight change in the temperature of the iion. 



On these grounds therefore it is presumed, that the follow- 

 ing experiments would be entided to some notice, as they 

 serve to reconcile all diese apparently contradictory state- 

 ments ; but the principal reason which has induced me to lay 

 them belbre the Royal Society is, the anomalous action which 

 they have been the means of discovering, while the iron passes 

 through the sliades of bright red and red, already alluded to 

 in the preceding part of this paj)er, and which, to the best of 

 my knowledge, has never been noticed by any author. 



Exj)rrimenis on the anomalons Atlmction of heated Iron -whicJi 



takes i^lace xdiile the Metal retains the bright red and red 



heat. 



I have already observed, that this anomalous action was 

 noticctl while v.e were pursuing other experiments, and that 

 th;)se which li)llo\v, were wholly directed to an examination of 

 these inegularilies. 



X'nl.CO. N\), 2;).-). .Vrn'. 1H22. Xx In 



