CLOTHING AND THE ATMOSPHERE. 795 



the persistence of porosity. The fibers of wool, even when moistened, 

 lose but little of their elasticity and do not allow the pores to close, 

 while the filaments of linen, cotton, and silk become quite soft under 

 the influence of moisture, and do not resist the invasion of the water. 

 For this reason damp wool cools us much less than damp linen. A linen 

 or silken shirt is cooler than a woolen one, because it more completely 

 sponges off the sweat and exposes it to evaporation. These facts illus- 

 trate clearly the capital influence which space between the fibers exer- 

 cises on the physical properties of cloths. A cloth must evidently be 

 considered as a tissue formed of textile matter and air. The proper- 

 ties of the fibers themselves can give us only the most incomplete 

 ideas of the physical effects which their assemblage would bring about. 

 The arrangement of the fibers and the manner in which they are pre- 

 pared are most frequently the important points. There is reason to 

 believe that by looking along this road, still so little explored, we shall 

 reach results that will permit us to make a better use of some of the 

 innumerable textile materials which Nature has put at the disposition 

 of our industry. 



Hygienists, in speaking of different cloths, are generally contented 

 with classifying them vaguely in the order of conductibility, and of 

 designating by that word the greater or less facility they offer to the 

 passage of heat. It is agreed that conductibility decreases in the fol- 

 lowing order : linen or hemp cloth, cotton, silk, and wool. Cloths 

 made of linen, hemp, and cotton, are considered the coolest. They 

 are readily moistened and cool the skin by both conductibility and 

 evaporation. Linen, whether made of hemp or flax, is, says M. Bou- 

 chardat, of all substances destined for clothing, the one that most 

 favors the affections resulting from the impression of moisture on the 

 skin. But with many persons the coolness and pleasant feeling of 

 linen are very highly appreciated as advantages. 



Cotton cloth lets less heat escape, absorbs and retains a part of the 

 perspiration, and cools less rapidly by evaporation ; its use is generally 

 more advantageous than that of linen. An opinion or prejudice pre- 

 vails widely that cotton is less healthful than linen, based on the fact 

 that, being a less perfect conductor and rougher, cotton irritates the 

 skin more than linen does. Examined with the microscope, the fibers 

 of cotton appear angular and stiff, while those of linen are round and 

 supple. Cotton is not agreeable in cutaneous affections, but wool, in 

 such cases being more hairy and warmer, would be still more disagree- 

 able. This is the only condition, says M. Bouchardat, in which any 

 other substance than very fine, well-washed, and well-worn linen can 

 be worse than it. Aside from this, cotton cloth has the advantage 

 over linen of being warmer in winter, and, in summer, of not exposing 

 the body to the dangers of too rapid cooling. It should be used in 

 preference to linen by inhabitants of cold and moist countries. Wool 

 is still more irritating than cotton, on account of the stiffness of the 



