VOL. LXXVir.] PHILOSOPHICAL TRANSACTIONS. 26\ 



divisions being = g ^ ; 3^ part of a mark, consequently 1000 of these parts 

 make about 52^ grains troy. It seems that those bodies which are the most 

 easily wet, or which receive water, in its unelastic form, with the greatest ease, 

 are not those which in all cases attract the watery vapour dissolved in the air with 

 the greatest force. Perhaps the apparent dampness of linen, to the touch, 

 arises more from the ease with which that substance parts with the water it con- 

 tains, than from the quantity of water it actually holds : in the same manner as 

 a body appears hot to the touch, in consequence of its parting freely with its 

 heat, while another body, which is actually at the same temperature, but which 

 withholds its heat with greater obstinacy, affects the sense of feeling much less 

 violently. 



It is well-known, that woollen-clothes, such as flannels, &c. worn next the 

 skin, greatly promote insensible perspiration. May not this arise principally 

 from the strong attraction which subsists between wool and the watery vapour 

 which is continually issuing from the human body ? That it does not depend 

 entirely on the warmth of that covering, is clear ; for the same degree of 

 warmth, produced by wearing more clothing of a different kind, does not pro- 

 duce the same effect. The perspiration of the human body being absorbed by a 

 covering of flannel, it is immediately distributed through the whole thickness of 

 that substance, and by that means exposed by a very large surface to be carried 

 off by the atmosphere ; and the loss of this watery vapour, which the flannel 

 sustains on the one side, by evaporation, being immediately restored from the 

 other, in consequence of the strong attraction between the flannel and this 

 vapour, the pores of the skin are disencumbered, and they are continually sur^ 

 rounded by a dry, warm, and salubrious atmosphere. 



I am astonished, that the custom of wearing flannel next the skin should not 

 have prevailed more universally. I am confident it would prevent a m.ultitude of 

 diseases ; and I know of no greater luxury than the comfortable sensation which 

 arises from wearing it, especially after one is a little accustomed to it. It is a 

 mistaken notion, that it is too warm a clothing for summer. I have worn it in 

 the hottest climates, and in all seasons of the year, and never found the least 

 inconvenience from it. It is the warm bath of a perspiration confined by a linen 

 shirt, wet with sweat, which renders the summer heats of southern climates so 

 insupportable ; but flannel promotes perspiration, and favours its evaporation ; 

 and evaporation, as is well known, produces positive cold. I first began to wear 

 flannel, not from any knowledge which I had of its properties, but merely on 

 the recommendation of a very able physician, Sir Richard Jebb ; and when I 

 began the experiments of which I have here given an account, I little thought 

 of discovering the physical cause of the good effects which I had experienced 

 from it ; nor had I the most distant idea of mentioning the circumstance. 



