283 



Of the Propagation of Heat 



placed in a mixture of pounded ice and pure water, 

 where it was suffered to remain four hours, in order that 

 the cake of ice in the jar might be brought to the tem- 

 perature of 32. 



The jar still standing in a shallow dish in the pounded 

 ice and water, the surface of which cold mixture was just 

 on a level with the surface of the ice in the jar, I covered 

 the top of the cake of ice with a circular piece of strong 

 paper, and poured gently into the jar 73 -J- oz., Troy, of 

 boiling-hot water, which filled it to the height of eight 

 inches above the surface of the ice. (See Plate II.) 



I then removed very gently the circular piece of paper 

 which covered the surface of the ice, and after leaving 

 the hot water in contact with the ice a certain number of 

 minutes, I poured it off, and, weighing immediately the 

 jar and the unmelted ice which remained in it, I ascer- 

 tained the quantity of ice which had been melted by the hot 

 water during the time it had been suffered to remain in 

 the jar. 



This experiment I repeated four times the same day 

 (i6th March, 1797), varying at each repetition of it the 

 time the water was permitted to remain on the ice. The 

 results of these experiments were as follows : 



From the results of these experiments it was plain that 

 a very considerable portion of the ice which was melted, 



