in a relative sense, signifies the sensation produced by the abstraction of heat from the body.
The nature of cold, and the methods of producing it artificially, have been treated of under the article CHEMISTRY, to which we refer the reader.
Great degrees of cold occur naturally in many parts of the globe in the winter-time. In the winter of 1780, Mr Wilton of Glasgow observed, that a thermometer laid on the snow sunk to 25° below 0; but this was only for a short time; and in general our atmosphere does not admit of very great degrees of cold for any length of time. In 1732, the thermometer at Petersburg stood at 28° below 0; and in 1737, when the French academicians wintered at the north polar circle, or near it, the thermometer sunk to 33° below 0; and in the Asiatic and American continent, still greater degrees of cold are very common.
The effects of these extreme degrees of cold are very surprising. Trees are burst, rocks rent, and rivers and lakes frozen several feet deep; metallic substances blister the skin like red-hot iron; the air, when drawn in by respiration, hurts the lungs, and excites a cough; even the effects of fire in a great measure seem to cease; and it is observed, that though metals are kept for a considerable time before a strong fire, they will still freeze water when thrown upon them.
When the French mathematicians wintered at Torneo in Lapland, the external air, when suddenly admitted into their rooms, converted the moisture of the air into whirls of snow; their breasts seemed to be rent when they breathed it, and the contact of it was intolerable to their bodies; and the alcohol, which had not been highly rectified, burst some of their thermometers by the congelation of the aqueous part.
Extreme cold very often proves fatal to animals in those countries where the winters are very severe; and thus 7000 Swedes perished at once in attempting to pass the mountains which divide Norway from Sweden. It is not necessary indeed, that the cold, in order to prove fatal to the human life, should be so very intense as has been just mentioned. There is only requisite a degree somewhat below 32° of Fahrenheit, accompanied with snow or hail, from which shelter cannot be obtained. The snow which falls upon the clothes, or the uncovered parts of the body, then melts, and by a continual evaporation carries off the animal heat to such a degree, that a sufficient quantity is not left for the support of life. In such cases, the person first feels himself extremely chill and uneasy; he begins to turn listless, unwilling to walk or use exercise to keep himself warm; and at last turns drowsy, sits down to refresh himself with sleep, but wakes no more. An instance of this was seen not many years ago at Terra del Fuego, when Dr Solander, with some others, having taken an excursion up the country, the cold was so intense, that one of their number died. The Doctor himself, though he had warned his companions of the the danger of sleeping in that situation, yet could not be prevented from making that dangerous experiment himself; and though he was awakened with all possible expedition, his body was so much shrunk in bulk, that his shoes fell off his feet, and it was with the utmost difficulty that he was recovered.
In those parts of the world where vast masses of ice are produced, the accumulation of it, by absorbing the heat of the atmosphere, occasions an absolute sterility in the adjacent countries, as is particularly the case with the island of Iceland, where the vast collections of ice floating out from the northern ocean, and stopping on that coast, are sometimes several years in thawing. Indeed, where great quantities of ice are collected, it would seem to have a power like fire, both augmenting its own cold and that of the adjacent bodies. An instance of this is related under the article EVAPORATION, in Mr Wedgewood's experiment, where the true cause of this phenomenon is also pointed out.
in Medicine. See MEDICINE Index.