On the Formation of Bottom Ice. 405 



labouring, and the early nebulous condition of cosmical 

 matter, so necessary for almost all geological reasoning, proved 

 to demonstration by the labours of our excellent observer, 

 whose results we have detailed in this article. 



ON THE FORMATION OF BOTTOM ICE EST SALT 

 AND FRESH WATER. 



Translated from the Swedish, of E. Edlund, 

 BY "AN OLD BUSHMAN." 



As is well known to all, fresh water has its greatest solidity 

 and, consequently, its greatest weight, at a temperature of 

 4° Cent.,* and it is principally on this account that fresh- 

 water lakes, with still water, freeze up at the approach of 

 winter. When the upper layer of water on the surface of 

 such a lake becomes chilled on account of its contact with the 

 cold air, it sinks to the bottom, and water of a higher degree of 

 temperature rises from the depths of the lake, and takes its 

 place on the surface. This becomes chilled in its turn, sinks 

 down, and leaves a place for a new layer of water, which rises 

 from the bottom, and so on. After the whole mass of water 

 has in this manner become chilled to a temperature of 

 4° Cent., this circulation ceases, and the cooling process 

 goes on in another form. When the surface water has 

 attained a temperature lower than 4° Cent., it remains 

 on the surface, because it is then lighter than the water which 

 lies below it. On this account the uppermost layer of water 

 can be at freezing-point, and become ice, whilst the temperature 

 of that below it is considerably above freezing point. 



If we follow the old opinion, that the formation of ice can 

 only take place on the free surface of the water, bottom ice 

 must be regarded only as a fable. This phenomenon, however, 

 like many others in the science of natural history, shows the 

 folly of denying the existence of any fact in nature which we 

 are unable to explain by any received theory ; for it is now 

 plainly shown that the formation of bottom ice is a certainty 

 which cannot be denied. 



This bottom ice in general consists of a loose, spongy matter, 

 in appearance somewhat resembling wet, half-thawed snow, 

 and generally assuming the shape of round plates, of diiferent 

 sizes and thickness. It often forms around stones, etc., which 

 lie on the bottom. When the first ice formation takes place, 



* In the Centigrade scale 4° corresponds with 39 '2 Fahrenheit's scale. 



