There is a considerable variety of climate in Canada, from the northeast, chilled by the winds of the Atlantic,[156] to the southwest, five degrees lower, and approaching the center of the continent; the neighborhood of ranges of bare and rugged mountains,[157] has also a marked effect upon the temperature of different localities. However, in all parts the winters are very severe, while the heat of summer is little inferior to that of the tropics. But, on the whole, the clear blue sky, unobscured by fog or mist, and the pure elastic air, bespeak the salubrity of these provinces in all seasons. In Lower Canada the extreme severity of the winter is, in a measure, caused by the vicinity of the range of lofty and rugged mountains, as well as by its more northern position. The fall of snow commences in November, but seldom remains long on the ground till December; in that month constantly successive falls of snow rapidly cover the whole surface of the country. Toward the end of December the heavy clouds disperse, and the rude storm is followed by a perfect calm; the air becomes pure and frosty, and the skies of a clear and beautiful azure. The River St. Lawrence[158] is frozen over every winter from Montreal to the Richelieu Rapids, but from thence to Quebec only once in about five years; at other times, however, enormous fields and masses of ice drift up and down with the changing tides, increasing or diminishing with the severity or mildness of the weather; where the Island of Orleans divides the Great River into two branches, the northern channel is narrow and less acted upon by tides; here these huge frozen masses are forced together by the winds and waters, and form an enormous bridge from shore to shore. The greatest degree of cold prevails toward the end of January, for a few days occasionally so intense that the human frame can scarcely endure exposure to it for any length of time. When winter has set in nearly every bird disappears, and few wild animals are any longer to be seen; some, like the bear, remain torpid, others change their color to a snowy white, and are rarely observed. Rocks of the softer kinds are often rent asunder, as if with the explosion of gunpowder, by the irresistible expansive power of the frost.[159] Dogs become mad from the severity of the cold, and polished iron or other metal, when exposed in the air for a little time, _burns_ the hand at the touch as if it were red hot.[160] During the still nights of intense frost the woods send forth a creaking sound, like the noise of chopping with thousands of hatchets. Sometimes a brief thaw occurs in the middle of winter, when a very extraordinary effect, called by the Canadians _ver glas_, is occasionally produced upon the bare trees: they are covered with an incrustation of pure ice from the stem to the extremities of the smallest branches; the slight frost of the night freezes the moisture that covered the bark during the day; the branches become at last unable