observed on the Glaciers of Chamouny, &c. 27 
being so, it is not even a proof that it is from the fluid that the 
thermometer receives the heat which it acquires ; for it is possible, 
for aught we know to the contrary, that it may be occasioned 
by the radiation of the hot body placed at the surface of the fluid. 
In the experiments of which I have given an account, in my 
Essay on the Propagation of Heat in Fluids, great masses, many 
pounds in weight, of boiling hot water, were made to repose for 
a long time (three hours) on a cake of ice, without melting but 
a very small portion of it ; and, on repeating the experiment 
with an equal quantity of very cold water, (namely, at the 
temperature of 41 0 Fahrenheit,) nearly twice as much ice was 
melted in the same time. In these experiments, the causes of 
uncertainty above mentioned did not exist : and the results of 
them were certainly most striking. 
The conclusions which naturally flow from those results, 
have always appeared to me to be so perfectly evident and in- 
disputable, as to stand in no need, either of elucidation, or of 
farther proof. 
If water be a conductor of heat, how did it happen that the 
heat in the boiling water did not, in three hours, find its way 
downwards to the cake of ice, on which it reposed, and from 
which it was separated only by a stratum of cold water, half an 
inch in thickness ? 
I wish that gentlemen who refuse their assent to the opinions 
I have advanced respecting the causes of this curious pheno- 
menon, would give a better explanation of it than that which I 
have ventured to offer. I could likewise wish that they would 
inform us how it happens, that the water at the bottoms of all 
deep lakes remains constantly at the same temperature : and, 
above all, how the cylindrical pits, above described, are formed 
E 2 
