THE SKIN. 225 



several layers of dresses, each one should be considerably 

 looser than the next one within, so that a layer of air may 

 be kept between them. In all these cases, the several strata 

 of air between the different garments, and in the meshes of 

 the loose textures of cloth, acting as non-conductors, prevent 

 the passage of heat. From this cause, the attic chamber, 

 which has nothing but the roof between it and the burning 

 sun or freezing air, is much hotter in the summer and colder 

 in the winter than the chamber below, which has the air 

 of the attic between it and the solar rays or the outer 

 atmosphere. 



540. The various materials of our garments linen, 

 cotton, silk, and woollen have different qualities, and are 

 consequently suitable for different persons and seasons. The 

 fibre of linen is round, pliable, smooth, ancf soft to the skin ; 

 it therefore makes a most agreeable garment. Yet it is a 

 good conductor, and allows the heat to pass off rapidly, and 

 therefore feels cold when it touches the skin. Moreover its 

 fibre is porous, and absorbs and retains the water of perspira- 

 tion. Water being a still better conductor than linen, those 

 who wear this cloth are chilled after sweating, even in a hot 

 day. For this reason, linen is more and more abandoned as 

 an article for under-wear in hot climates. 



541. Cotton is a worse conductor, and therefore warmer 

 than linen. It is also soft, though less so than linen, and 

 less pleasant to the touch, for its fibres are not rounded, but 

 " are flat and have sharp edges," which irritate some delicate 

 skins. But it does not absorb moisture, and for this reason 

 it is the favorite and proper under-dress of all climates. 



542. Silk is not so good a conductor, and is warmer than 

 cotton. Its fibres are round and pliable, and it makes a 

 pleasant garment for the skin. It attracts no moisture, and 

 gives a sensation >f freshness to the surface when it touches 

 it. But, " on the slightest friction, it disturbs the electricity, 

 and then becomes a source of irritation," and in very delicate 

 and irritable constitutions it sometimes produces eruptions. 



543. Wool is the worst conductor of heat, and is there- 



