330 APPENDIX BY THE 



to sink bodily into the ice, as to maintain that the ice 

 sinks in the water. 



There is a coating of ice, however, which is found not 

 unfrequently beneath the water, and that in running 

 streams. But this is ground ice, as it is called, and has 

 been formed where it is found, adhering to the soil which 

 forms the bed of the river, and has never sunk from the 

 surface. On the contrary, once loosened from its hold, it 

 not only rises itself, but brings with it pebbles, gravel, &c. 

 The formation of this ground ice has attracted the atten- 

 tion of distinguished scientific men. The slower mo- 

 tion of water at the bottom than on the surface of a 

 stream, connected with the fact that crystals of ice form 

 naturally and very readily on pointed and rough bodies, 

 such as the stones or vegetable substances at the bottom 

 of streams, have been supposed to be the causes of this 

 ground ice. 



