ing upon the absorption of their summer fat. In these animals, the temperature falls during hybernation, to obviate the effect of which, they ensconce themselves under shelter, and many of them accumulate materials around them, to exclude the cold. It is singular that exposure to intense cold wakens a hybernating animal. Cold as a mortal agent, destroys by producing "sleep that knows no waking." The hybernating animal wakened by cold, sinks under its influence into a new sleep, and dies.

In Captain Cook's first voyage, the effects of cold inducing this sleep are strikingly instanced. The scene occurred in the island of Terra-del-Fuego.Dr. Solander, Mr. Banks, and several other gentlemen, had ascended the mountains of that cold region for the purpose of botanizing and exploring the country. "Dr. Solander, who had more than once crossed the mountains which divide Sweden from Norway, well knew that extreme cold, especially when joined with fatigue, produces a torpor and sleepiness that are almost irresistible. He, therefore, conjured the company to keep moving, whatever pain it might cost them, and whatever relief they might be promised by an inclination to rest. "Whoever sits down,' said he, will sleep; and whoever sleeps, will wake no more. Thus at once admonished and alarmed, they set forward; but while they were still upon the naked rock, and before they had got among the bushes, the cold became suddenly so intense, as to produce the effects that had been most dreaded. Dr. Solander

himself was the first who felt the inclination, against which he had warned others, irresistible; and insisted upon being suffered to lie down. Mr. Banks entreated and remonstrated in vain; down he lay upon the ground, although it was covered with snow, and it was with great difficulty that his friend kept him from sleeping. Richmond, also, one of the black servants, began to linger, having suffered from the cold in the same manner as the doctor. Mr. Banks, therefore, sent five of the company, among whom was Mr. Buchan, forward, to get a fire ready at the first convenient place they could find; and himself, with four others, remained with the doctor and Richmond, whom, partly by persuasion and entreaty, and partly by force, they brought on; but when they had got through the greatest part of the birch and swamp, they both declared they could go no further. Mr. Banks again had recourse to entreaty and expostulation, but they produced no effect. When Richmond was told that if he did not go on he would in a short time be frozen to death, he answered that he desired nothing but to lie down and die. The doctor did not so explicitly renounce his life; he said that he was willing to go on, but that he must first take some sleep, though he had before told the company to sleep was to perish. Mr. Banks and the rest found it impossible to carry them; and there being no remedy, they were both suffered to sit down, being partly supported by the bushes; and in a few minutes they fell into a profound sleep. Soon after, some of the people who had

been sent forward returned, with the welcome news that a fire was kindled about a quarter of a mile further on the way. Mr. Banks then endeavoured to awake Dr. Solander, and happily succeeded. But though he had not slept five minutes, he had almost lost the use of his limbs, and the muscles were so shrunk, that the shoes fell from his feet: he consented to go forward with such assistance as could be given him, but no attempts to relieve poor Richmond were successful."

The following remarks by Dr. Macnish, in relation to this subject, are extremely interesting. The practical rule is excellent, and the fact explains how animals may hybernate in snow.

"If a person is unfortunate enough to be overtaken in a snow-storm, and has no immediate prospect of extrication, he should, if the cold is very great, and the snow deep, sink his body as much as possible in the latter, leaving only room for respiration. By this plan, the heat of the body is much better preserved than when exposed to the influence of the atmosphere, and life has a greater chance of being saved; for the temperature of the snow is not lower than that of the surrounding air, while its power of absorbing caloric is much less. It is on this principle that sheep live for such a length of time enveloped in snow-wreaths, while, had they been openly exposed, for a much less period, to a similar degree of cold, death would inevitably have ensued."

Dr. Darwin mentions that a person placed upon a

mill-stone, revolving rapidly, is thrown into sleep. I cannot find the facts upon which this statement is grounded. But I conclude that pressure upon the brain, and stupor, would be the natural physical and physiological consequences of such an experiment.— Dr. Macnish observes, "By lying flat upon a millstone while performing its revolutions, sleep is soon produced, and death without pain would be the result, if the experiment were greatly protracted." Sir John Sinclair says, “The celebrated engineer, Brindley, often saw the experiment tried, of a man extending himself across the large stone of a corn-mill, and gradually falling asleep by the stone whirling round, before the stone had gained its full velocity."

A hearty meal produces somnolency. The effect probably ensues from the temporary exhaustion of the brain, caused by the determination of the blood and nervous energy to the stomach. The sleep, which follows, is heavy and disturbed. It should not be indulged in. It carries no refreshment with it. The labouring digestion requires the stimulus of waking to help it. A hearty meal should therefore never be taken late at night;-then, in addition to the reasons against it, which have been stated, the system is already exhausted by the day it has toiled through. A good meal at night, however, may be taken with another view. Suppose you have to watch, and not to sleep it is certain that food is, to a certain extent, a substitute for sleep, and in that case, may be used as such. This means, however, can be resorted to by

those only whose digestion is strong. I have already described (p. 56,) the extraordinary quantity of food which Captain Barclay consumed in his match of one thousand miles in a thousand hours. It was the strength of his stomach (after his courage and endurance) which carried him through that match. The food he chymified was a substitute for sleep.

It has been remarked that those who eat heartily, and have strong digestive powers, usually sleep much. Those who do so, try their constitutions severely, and fall into dangerous plethora. The habit becomes gross and overloaded, and exposed to a troop of illnesses. One mode of relief is occasionally present in such cases in the shape of profuse perspiration. But this, as it is highly relaxing, lowers the tone of the system, and weakens the person who so indulges in body and in mind.

Preparation for Sleep.-A sleeping-apartment should be well ventilated: it is therefore desirable in winter to have a fire in a bed-room, or in a dressingroom opening into it. The bed had better stand detached from the wall for the same purpose. The curtains should not be drawn close; the quantity of covering should be regulated by the temperature of the weather. Dr. Rush observes, "Warm bed-clothes are especially proper to preserve or increase the heat of old people. From the neglect of this observance, they are often found dead in their beds in the morning, after a cold night, in all cold countries. The