On the formation of Ice. 181 
water up, by which almost exclusively the water was cool- 
ed, before it arrived at 40°, being in a great measure pre- 
vented, after the first film of ice is formed on the sushiies 
Mankind are littke aware how much they are indebted to 
such apparently trivial laws for their comfort, and indeed 
for their very existence ; for it is undeniable, that had the 
creator omitted to endue water with this unparalleled pe- 
culiarity of contraction, and had ice been as good a a 
ductor of heat as the metals, the polar seas would, even 
the early ages, have been frozen to the bottom; all I other 
waters, not excepting the oceans within the tropics, would 
have been successively converted into a solid as enduring 
as granite; vegetable and animal life would have become 
extinct ;—the very atmosphere might have congealed, and 
in the language of Dr. Black, all Piety would have be- 
come a silent, lifeless, and isis 
n the case of congelation which bits cheited these Peleg, 
there was another circumstance worthy of observation. _ 
~The layers of ice were much more transparent ii in at di- 
rection of their length than in the opposite ; this arose from 
the distorted refraction of light occasioned by innumerable 
air bubbles, from the size of duck shot to that of a small - 
pin’s head, which were, in every aie, to be observed 
at the junction of the layers, and at the top of each par- 
ticular layer, excepting that on the surface, where there 
were none. If we mistake not, these peculiarities can be 
satisfactorily explained. It is well known that all natu 
waters contain air in solution, and that itis. expelled by i- 
ing, by the air pump, and by freezing. Say 
On the surface of the water, wa the first i ito ice 
° after the first ier) r of ice was produced, the 
air bubbles that were extricated by tl the jjling of the wa- 
ter next —— boa of whe aa eae ‘i and ice, and 
Had 
