252 Account of a curious Phenomenon 



ally in depth, as long 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 temperature, the 

 phenomenon may easily be explained ; but it appears to 

 me to be inexplicable on any other supposition. 



The quiescent mass of water by which the pit remains 

 constantly 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 undoubtedly communicate some small degree 

 of heat to those particles of the fluid with which this 

 warm air comes into immediate contact; and the par- 

 ticles 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 

 communicate 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 



