112 Mr. H. Wilde. On the Influence of Temperature [June 11, 



into a cavity formed in the upper end of the bar. These temperatures 

 were afterwards verified, and similar results obtained, when the bar 

 was plunged into crucibles of the melted metals. The temperature 

 of 100 C. was determined by plunging the bar into boiling water 

 during the period of cooling. For temperatures below zero, a bath of 

 solid carbonic acid and ether was employed, into which the bar was 

 placed until it was cooled down to - 76 C. The refrigerating arrange- 

 ment was so effective, from the large supply of solid carbonic acid 

 at my disposal, that a globule of mercury placed in the cavityat the 

 upper end of the bar remained solid several minutes after the comple- 

 tion of the experiment. 



All the experiments detailed in the following table were made with 

 descending temperatures, as strictly concordant results were not 

 obtained with definite increments of heat, especially for the lower 

 ranges. 



The electro-magnet was excited by a constant current of 20 

 amperes. 



Table I. 



The principal result shown by these experiments is the continued 

 diminution of the magnetic power of the iron, from the lowest to the 

 highest temperature to w r hich the bar was subjected. 



As it was of importance to determine whether iron entirely loses 

 its magnetic power by heating, the temperature of one of the bars was 

 raised to incipient fusion ; but when the bar was carefully balanced 

 there still remained in it a measurable amount of magnetic force 

 when the electro-magnet was brought into action. 



