304 



Of the Propagation of Heat 



the boiling-hot water, taking the mean of five experi- 

 ments (those No. 45, 46, 47, 48, and 49), was no more 

 than 399! grains. But the results of the four following 

 experiments are, if possible, still more surprising. 



These experiments were made with water at the tem- 

 perature of 61°, the temperature of the air of the room 

 being at the same time 61° ; in the two first of these ex- 

 periments the jar was kept plunged to its brim in a mix- 

 ture of snow and water ; in the two last its lower part 

 only, namely, as high as the level of the surface of the 

 ice, was surrounded by this cold mixture, its upper part 

 being naked, and surrounded by the air of the room. 



In each of the experiments (as in those which preceded 

 them), before the water was poured into the jar the sur- 

 face of the ice was covered to the height of 0.956 of an 

 inch with ice-cold water, in order more effectually to de- 

 fend it against the effects of the temporary motions into 

 which the water employed to melt the ice was unavoid- 

 ably thrown in the performance of this operation ; and 

 the same quantity of water was always used, namely, 731 

 ounces, Troy, or as much as was sufficient to fill the jar 

 to the height of 8 inches. 



These experiments are remarkable, not only on ac- 

 count of the very small difference in the quantities of ice 



