24 Count Rumford's Account of a curious Phenomenon 
as the hot weather continues ; but that they are frozen up, and 
disappear, on the return of winter. 
I would ask those who maintain that water is a conductor of 
heat, how these pits are formed ? On a supposition that there is 
no direct communication of heat between neighbouring particles 
of that fluid, which happen to be at different degrees of tem- 
perature, the phenomenon may easily be explained ; but it ap- 
pears to me to be inexplicable on any other supposition. 
The quiescent mass of water, by which the pit remains con- 
stantly filled, must necessarily be at the temperature of freezing ; 
for it is surrounded on every. side by ice: but the pit goes on to 
increase in depth, during the whole summer. From whence comes 
the heat that melts the ice continually at the bottom of the pit ? 
and how does it happen, that this heat acts on the bottom of the 
pit only, and not on its sides ? 
These curious phenomena may, I think, be explained in the 
following manner. The warm winds which, in summer, blow 
over the surface of this column of ice-cold water, must undoubt- 
edly communicate some small degree of heat to those particles 
of the fluid with which this warm air comes into immediate 
contact ; and the particles of the water at the surface so heated, 
being rendered specifically heavier than they were before, by 
this small increase of temperature, sink slowly to the bottom of 
the pit ; where they come into contact with the ice, and commu- 
nicate to it the heat by which the depth of the pit is continually 
increased. 
This operation is exactly similar to that which took place in 
one of my experiments, (See my Essay on the Propagation of 
heat in Fluids, Experiment 17,) the results of which, no person, 
to my knowledge, has yet explained. 
