74 EOYAL SOCIETY OF CANADA ' 



Mr. Knight, the celehrated hotanist, has related an observation in 

 the 106th volume of the Philosophical Transactions, which is the more 

 valuable^ as it seems in some respects to afford a clue to the secret of 

 the formation of ice on the bottom of rivers. 



" In a morning which succeeded an intensely cold night, the stones 

 in the rocky bed of the river appeared to be covered with frozen mat- 

 ter, which reflected a kind of silvery whiteness, and which, upon 

 examination, I found to consist of numerous frozen spicula crossing 

 each other in every direction, as in snow, but not having anywhere, 

 except very near the shore, assumed the state of Arm compact ice. The 

 river was not at this time frozen over in any part; but the temper- 

 ature of the water was obviously at the freezing point, for small pieces 

 of ice had everywhere formed upon it in its more stagnant parts near 

 the shores; and upon a mill-pond, just above the shallow streams (in 

 the bottom of which I had observed the ice), I noticed millions of 

 little frozen spicula floating upon the water. At the end of this mill- 

 pond the water fell over a low weir and entered a narrow channel, 

 where its course was obstructed by points of rock and large stones. By 

 these, numerous eddies and gyrations were occasioned, which apparently 

 drew the floating spicula under water; and I found the frozen matter 

 to accumulate much more abundantly upon such parts of the stones 

 as stood opposed to the current, where that was not very rapid below 

 the little falls or very rapid parts of the river. I have reason to 

 believe that it would have accumulated in very large quantities if the 

 weather had continued sufficiently cold; for I had been informed on 

 good evidence, that, some years before, the whole bed of the river 

 in the part above mentioned had been covered over with a thick coat 

 of ice. 



" On some large stones near the shore, of which parts were out 

 of the water, and upon pieces of native rock, under similar circum- 

 stances, the ice beneath the water had acquired a firmer texture, but 

 appeared from its whiteness to have been first formed of congregated 

 spicula, and to have subsequently frozen into a firm mass, owing to 

 the lower extremity of the stone or rock. Ice of this kind extended 

 in a few places eighteen inches from the shore, and lay three or four 

 inches below the level of the surface of the water, and did not dis- 

 solve so rapidly as that which was deposited upon stones more distant 

 from the shores." 



In the 11th of February, 1816, the engineers of bridges and roads 

 residing at Strasbnrg, saw above the bridge of Kelil that many parts 

 of the channel of the Ehine were covered with ice. About ten o'clock 

 a.m. this ice became loose, rose to the surface, and floated. 



