Page:Early western travels, 1748-1846 (1907 Volume 8).djvu/169

 surface of water becomes impregnated with frost, its weight presses it to the bottom, and a new supply rises to take its place. Thus, a revolution is continued, until the whole mass becomes chilled to a certain degree, and then the surface congeals. The necessary quantity of cold in the mass, to produce this effect upon the surface, is about thirty degrees. The depth of Lake Ontario is very great. Attempts to ascertain its depth have, in many places, been in vain: various parts of the centre have been sounded with a line of three hundred and fifty fathoms, without success. It must require a great degree, and a long continuance of cold, so to chill so deep a body of water, as to produce the congelation of its surface.

As to the influence of wind, it produces, as has been observed, an undulation of water, so as to prevent that regular operation of frost, which is necessary to congelation. The land on the north east of Lake Ontario, is low; and the Lake is frequently agitated by storms.

As another supposed cause of the unfrozen state of this lake in the winter season, it may be presumed that there are beds of salt at the bottom of this body of water, which neutralize, in some measure, the elements of frost, as they descend beneath the surface. There are numerous salt springs on both sides of the Lake, and in its immediate vicinity.

Further: there is reason to believe, that there are warm springs in the bed of this lake. In the vicinity of it, on the Canada side, hunters frequently meet with spots of ground, about two or three acres in extent, the surface of which is, in the winter, entirely free from snow; and yet these spots are surrounded with snow to the depth of six or eight feet. Upon these places the snow, when it falls, instantly {67} melts, both that which falls upon the ground, and upon the trees.