rves? The
nitric acid will dissolve metals, and this solution will go on more
quickly if heat be applied; but surely the nitric acid is the
solvent, the heat being only an aiding cause.

But though the human body has been so wisely constructed, as to bear,
without inconvenience, a considerable variation of temperature; yet
this latitude has its limits, which depend upon the capability of
extricating heat from the atmosphere. There must be a limit below
which the diminution of heat takes place faster than its production.
If this be continued, or increased, the heat of the animal must
diminish, the functions lose their energy, and an insuperable
inclination to sleep is felt, in which if the sufferer indulge, he
will be sure to wake no more.

This is confirmed by what happened to Sir Joseph Banks and his party
on the heights of Terra del Fuego. Dr. Solander, who had more than
once crossed the mountains which divide Sweden from Norway, well knew
that extreme cold produces an irresistible torpor and sleepiness, he
therefore conjured the company to keep always in motion, whatever
exertion it might require, and however great might be their
inclination to rest. Whoever sits down, says 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
rocks, the cold was so intense, as to produce the effects which had
been so much dreaded. Dr. Solander himself was the first who found
the inclination against which he had warned others, irresistible; and
insisted on being suffered to lie down. Sir Joseph entreated and
remonstrated in vain; he lay down upon the ground, though it was
covered with snow; and it was with great difficulty that his friend
kept him from sleeping. One of his black servants also began to
linger, having suffered from the cold in the same manner as the
Doctor. Partly by persuasion, and partly by force, they were got
forwards; soon however they both declared that they would go no
further. Sir Joseph had recourse again to entreaty and expostulation,
but these produced no effect: when the black was told, that if he did
not go on, he would shortly be frozen to death; he answered, that he
desired nothing so much as to lie down and die. The Doctor did not so
explicitly renounce his life, but said, he would go on, if they would
first allow him to take some sleep, though he had before told them,
that to sleep was to perish. They b