Rivers dit/ring Winter. 125 



ter to the extent of two or three feet. The cold continuing, the 

 ice soon shewed itself in the deepest parts. 



In places where the water flowed over the hare rocJcs^ Des- 

 marest saw no vestige of ice. On the contrary, it was rapidly 

 formed in great abundance, especially where there was any 

 quantity of gravel : in some parts it was two feet thick. 



According to Desmarest, " it was from the lower part which 

 touched the bottom, that the flakes of ice successively increased. 



The ice already formed was continually raised up by 



the expansive force of that which was in the act of formation. 



In watching its motion, I have seen," said he, " that 



certain flakes of ice zvere raised up five or six inches in a single 

 night. Some of them were, in consequence of the daily and to- 

 lerably equal mider-additions, believed to form, in this manner, 

 islands of ice, which appeared above the running water."*' 



No one has hitherto corroborated this mode of increase of ice 

 under water. It is to be regretted that Desmarest did not ex- 

 plain the nature of the observation which induced him to come 

 to such a singular result. Had he, for example, deposited on the 

 flakes of the ice at the bottom objects which always remained 

 visible, while, in rising, all the twenty-four hours, the flakes 

 actually approached the surface of the water, it certainly would 

 have been worth while giving an explanation. 



When, in consequence of a cloudy sky, the atmovspherical 

 temperature experiences little variation throughout the day and 

 night, the ice at the bottom of the water, according to Desmarest, 

 uniformly increases every twent}'-four hours. On the contrary, 

 when the sun shews itself, the ice does not increase during the 

 day. The difl\?rent layers which are produced during the night 

 after an interval of five or six hours of repose, form distinct 

 beds, which are easily disunited. The current then detaches 

 each layer of ice from the lower one, to which it adheres but 

 feebly, and the river begins to carry it along. 



M. Beaun, a bailiff" at Weld Wilhelmsbourg, on the Elbe, 

 published many dissertations in 1788, in which the existence of ice 

 on the bottom of a river is established, either by his own obser- 

 vations or the unanimous declarations of fishermen, procured 

 after a most anxious investigation. 



