Dress, with reference to heat : being a lecture written for, and published by the Australian Health Society / by Walter Balls-Headley.

Balls-Headley, Walter.

Date:: 1876

Credit: Dress, with reference to heat : being a lecture written for, and published by the Australian Health Society / by Walter Balls-Headley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

13/44 (page 11)

$What has happened ? Tlie perspiration has been sui^plied to the surface of the skin ; the lieat of the body has evaporated H ; and tlie cold air without has removed so much of the heat, that the vapour is unable longer to maintain that form, and returns to tlie form of water ; which in our breath, under similar circumstances, we find deposited in drops on the moustache or muffler. With regard to the quantity of heat so removed, it is a matter of great importance, whether the outer air be dry or moist; that is, whether it already contains a considerable quantity of vapour or not; for, if saturated, it can receive no more, and evaporation ceases. This condition is well known to laundresses, since, when the air is thus satvu-ated, though it be hot and rapidly circulating^ as in a wind, wet clothes on a line will not dry; that is, their moisture will not evaporate. So on a hot-wind day, when the air is full of moisture the perspiration cannot evaporate, and we sit in wet clothes, and are greatly oppressed by want of removal of our superfluous heat. On the other hand, so long as heat be perfectly dry, we are able to sustain an enormously high temperature. Thus iron founders have, in the ordinary coux\se of work, entered a furnace at a temperature of 350 deg., of which the floor was red-hot; and Chabert, the Salamander, at a temperature of from 400 deg. to 600 deg.; it being remembered that water boils at 2] 2 deg. The safeguard in all these cases was the dryness of the air, and consequent capacity for evaporation from the body. The condition of rest or motion of the surrounding air much influences our sensations and capacity of endurance. Thus, if the air be still, we can endure a temperature much below what otherwise would aflect us greatly to our inconvenience. Thus, in Norway I was able in winter to sleigh with comfort in a temperature 45 deg. below the freezing point, so long as the air was still: but if there were wind, even above this heat one lost sensation in one's extremities, though clothed in furs. So if suitably dressed, we are warm in a still, open air temperature 20 or 30 deg. below that of the room we have just left; })ut are$