* And sob, their blue eyes. l. 184. The bath at Buxton being of 82 degrees of heat is called a warm bath, and is so compared with common spring-water which possesses but 48 degrees of heat, but is nevertheless a cold bath compared to the heat of the body which is 98. On going into this bath there is therefore always a chill perceived at the first immersion, but after having been in it a minute the chill ceases and a sensation of warmth succeeds though the body continues to be immersed in the water. The cause of this curious phenomenon is to be looked for in the laws of animal sensation and not from any properties of heat. When a person goes from clear day-light into an obscure room for a while it appears gloomy, which gloom however in a little time ceases, and the de∣ficiency of light becomes no longer perceived. This is not solely owing to the enlarge∣ment of the iris of the eye, since that is performed in an instant, but to this law of sen∣sation, that when a less stimulus is applied (within certain bounds) the sensibility increases. Thus at going into a bath as much colder than the body as that of Buxton, the diminu∣tion of heat on the skin is at first perceived, but in about a minute the sensibility to heat increases and the nerves of the skin are equally excited by the lessened stimulus. The sensation of warmth at emerging from a cold-bath, and the pain called the hot-ach, after the hands have been immersed in snow, depend on the same principle, viz. the increased sensibility of the skin after having been previously exposed to a stimulus less than usual.
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