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An Account of a curious Phenomenon observed on the Glaciers of Cha- 

 mouny ; together with some occasional Observations concerning the 

 Propagation of Heat in Fluids. By Benjamin Count of Rumford, 

 V.P.R.S. Foreign Associate of the National Institute of France, 

 Sfc. 8fc. Read December 15, 1803. [Phil. Trans. 1804, ;?. 23.] 



The fact here stated is as follows : At the surface of a solid mass 

 of ice, of vast thickness and extent, viz. the Glaciers of Montanverd, 

 certain pits are frequently met with, about seven inches in diameter, 

 and more than four feet deep, perfectly cylindrical, and always quite 

 full of water : their sides are smooth, or rather polished, and their 

 bottoms hemispherical and well defined. They are always found on 

 the level parts of the ice, and only in the summer season, increasing 

 gradually in depth as long as the hot weather continues, and dis- 

 appearing at the return of winter, when they are completely frozen 

 up. 



After calling upon those who maintain that water is a conductor 

 of heat, to solve this phenomenon according to their principles, and 

 pointing out to them, that as the water in these pits, being sur- 

 rounded by ice, must continually be at the freezing point of tempe- 

 rature, it is not the general heat of the fluid that can melt the ice at 

 the bottom of the pits, our author proceeds to give the following ex- 

 planation of this singular effect. 



The warm winds, he says, which in summer blow over the surface 

 of this column of ice-cold water, must evidently 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 ; and here they come in contact with 

 the ice, and communicate to it the heat by which the depth of the 

 pit is continually increased. 



Count Rumford mentions next the singular but well-authenticated 

 fact, of the equal temperature, at all seasons, of the water at the 

 bottom of lakes ; and shows how difficult, if not impossible, it must 

 be to explain this phenomenon on a supposition of water being a 

 conductor of heat. With a view to illustrate this subject, he gives 

 us hopes that he will soon favour us with some observations, show- 

 ing why all changes of temperature in transparent liquids must ne- 

 cessarily take place at their surfaces. Some further strictures are 

 next given, and certain difficulties are pointed out, on the cause of 

 the descent of heat in liquids. And, lastly, notice is taken of the 

 observations of Mr. Thompson of Edinburgh, on the experiments our 

 author had contrived to render visible the currents into which liquids 

 are thrown on a sudden application of heat or cold. The whole of 

 this discussion rests on the accuracy of his observations, which Mr. 

 Thompson had called in question, but in which he confidently asserts 

 there was no fallacy whatever. 



