LETTER XX. Quebec, 1808. N In giving you the striking features of the Canadian winter, I ought not to omit, that during the most severe cold in January, a great and very sudden change takes place almost every year, and continues for a day or two. From a most severe frost, when the thermometer shewed 60 degrees below the freezing point, it suddenly became so warm, that the thermometer shewed three degrees above freezing. In short, the weather this winter changed in a few hours from nearly the greatest degree of cold that ever was known here, to a complete thaw. It is a law of nature, that when fluids become solid, heat is given out to the atmosphere. On this principle, when water becomes ice, heat must be given out; and an accumulation of this heat may produce the thaw experienced in Canada, in the middle of winter. Such a great and sudden change is productive of very unpleasant sensations. The stoves, and winter clothing, are quite oppressive; and yet, it is dangerous to attempt to dispense with either, for you, every hour, look for a return of the cold weather, Fortunately, it does not in general continue many days; sometimes, however, it has been known to last ten or fourteen days; and, when this is the case, it is of very serious injury to the country in a variety of ways. It is extremely prejudicial to the health of the people. The streets are so inundated with water from the melting of the snow, that you cannot walk out; and the roads become so soft, and the rivers so full of water, that you cannot use a cariole, or travel, indeed, in any mode. But, what is a much more serious evil than all these things, the provisions which were destined to serve through the winter, become thawed, and are either destroyed altogether, or greatly injured. It is surprising, that although this circumstance has occurred frequently, and the people are subject to it every year, yet there is not much attention paid to putting the provisions in such a situation, and packing them up in such a manner, as to effectually prevent their being accessible to the warm air, during the thaw. It might be done very easily: Let them be packed in a tight box or cask, after being completely frozen, and this box or cask put into another, large enough to admit of its being surrounded with pounded ice and snow, which would act as a perfect nonconductor of heat, and preserve the contents of the inner box in their frozen state for a great length of time. The outer box should have holes in its bottom, to allow any water to run out, which might arise from the melting of the snow. This method has, I believe, been tried with success; but it is by no means in general use. During the thaw, a very extraordinary effect is produced, sometimes, on the trees. The Canadians call it a ver-glas. The tree, from the trunk to the point of the smallest branch, becomes incrusted with pure ice. There may be a small degree of frost during the night, which will freeze the moisture that covered the trees during the day; and it is probable that the external parts of the trees themselves, being cooled down below the freezing point, by the extreme cold of the previous weather, freeze the vapour, the moment it comes in contact with them; in the same way that the glass of a window in winter becomes incrusted with ice by the freezing of the moisture in the air of a room. The branches become at last so loaded with ice, that they can with difficulty support the weight of it; and if there happens to come a storm of wind, which was the case lately, the branches infallibly break off, and the destruction amongst trees of all sorts is immense. I see every day the effects of the last ver-glas. Branches of trees, from six to twelve inches in diameter, are seen every where hanging from the trees, completely broken down. I am told, that there can be nothing more curious or beautiful than one of those ice-incrusted trees when the sun shines upon it. Indeed, one can easily conceive that it must have the appearance of fairy work, or enchantment. In order that I might be able to ascertain correctly the state and changes of the atmosphere, both external and internal, I kept a thermometer suspended in a northern exposure, both on the outside and inside of the window. The thermometer on the inside was within half an inch of the glass. I observed a circumstance which marked strongly the extreme cold of the external atmosphere. It was between three and four o'clock in the afternoon; the room had been kept very warm during the whole of the morning; and, at the time, I observed that the thermometer shewed 73. though almost touching the ice on the window. withstanding of this, the inside of the window remained covered with ice, in the way you sometimes see it in England, in the morning, after a severe frost. Not This not only proves the severity of the frost, but also that glass is a very bad conductor of heat; else it would have been affected, and penetrated by the heat, in such a manner as to counteract the operation of the cold air of the atmosphere; but the cold was so intense, as to destroy and ab |