280 Of the Propagation of Heat 



of the experiment at 106, it appears that the mass of 

 hot water (which weighed 73^ ounces) was cooled 78 de- 

 grees, or from the temperature of 184 to that of 106, 

 during the experiment. Now, as it is known that 

 one ounce of ice absorbs just as much Heat in being 

 changed to water as one ounce of water loses in being 

 cooled 140 degrees, it is evident that one ounce of wa- 

 ter which is cooled 78 degrees gives off as much Heat as 

 would be sufficient to melt -j^ of an ounce of ice ; con- 

 sequently the 73-]- ounces of hot water, which in this ex- 

 periment were cooled 78 degrees, actually gave off as 

 much Heat as would have been sufficient to have melted 



140 



But the quantity of ice actually melted was only about 

 five ounces ; and hence it appears that less than one-eighth 

 fart of the Heat lost by the water was communicated to the 

 ice, the rest being carried off by the air. 



As the same quantity of hot water was used in this 

 experiment and in that, No. 15, which immediately pre- 

 ceded it, and as this water was contained by the same ves- 

 sel (the glass jar above described), it appears that ice 

 melts more than eighty times slower at the bottom of a 

 mass of boiling-hot water than when it is suffered to 

 swim on its surface. For, as in the experiment No. 15, 

 io| oz. of ice were melted in 2 minutes and 58 seconds, 

 5 ounces at least must have been melted in I minute and 

 29 seconds; but in the experiment No. 16, 2 hours, or 

 1 20 minutes, were employed in melting 5 ounces. 



The ice however was me! fed, .though very slowly, at the 

 bottom of the hot water; and that circumstance alone, 

 would have been sufficient to have overturned my hy- 

 pothesis respecting the manner in which Heat is propagated 

 in liquids, had I not found means to account in a satis- 



