HEAT. 47 



conventionally marked as 32. It may be said, how is this 

 reconcile able with the dynamical doctrine, for, according to 

 that, the solid should take from the mercury of the ther- 

 mometer more repulsive power than the liquid ; conse- 

 quently, the ice should contract the mercury more than the 

 water? 



My answer is, that in the proposition as thus stated, the 

 quantities of the water, ice, and mercury are not taken into 

 consideration, and hence a necessary dynamical element is 

 neglected : if the element of quantity be included, this objec- 

 tion will not apply. Let the thermometer, for instance, con- 

 tain 13 oz. of mercury, and stand at 100 ; if placed in con- 

 tact with an unlimited quantity of ice at 32, the mercury 

 will sink to 32. If the same thermometer be immersed in 

 an unlimited quantity of water at 32, the mercury sinks also 

 to 32 ; not absolutely, perhaps, because, however great the 

 quantity of water or ice, it will be somewhat raised in tem- 

 perature by the warmer mercury. This elevation of tempera- 

 ture above 32 will be smaller in proportion as the quantity 

 of water or ice is larger than the quantity of mercury ; and, 

 as we know of no intermediate state between ice and water, 

 the contact of a thermometer at a temperature above the 

 freezing point with any quantity of ice exactly at the freezing 

 point would, theoretically speaking, liquefy the whole, pro- 

 vided it had sufficient time ; for as every portion of that ice 

 would in time have its temperature raised by the contact of 

 the warmer body, and as any elevation of temperature above 

 the freezing point liquefies ice, every portion should be lique- 

 fied. Practically speaking, however, in both cases, that of 

 the water and of the ice, when the quantity is indefinitely 

 great the thermometer falls to 32, 



Now place the same thermometer at 100, successively 

 in one oz. of water at 32, and in one of ice at 32 ; we shall 

 find in the former case it will be lowered only to 54, and in 

 the latter to 32 ; apply to this the doctrine of repulsive force, 

 and we get a satisfactory explanation. 



