RELATIONS OF THE AIR TO OUR CLOTHING. 669 



the velocity of the surrounding air. We need not be anxious to make 

 our clothes prevent the access of air to our skin ; they have only to 

 regulate and moderate it to such a degree that our nerves may not 

 feel the air as something in motion. This degree is far from immo- 

 bility. When in the open air we believe it to be quite calm, there is 

 still a velocity in it of at least one foot and a half per second, or about 

 one mile per hour, as you heard before. 



Our clothing not only renders the air still around us, but it also 

 regulates its temperature by the heat which leaves our body ; we 

 heat our garments, and they continually heat the air passing through 

 the meshes and pores of the texture. We may compare our clothing 

 to a calorifer or stove, warmed by the heat emanating from our body's 

 engine for the purpose of warming the air round our surface. 



We do not feel the loss of heat which our clothing undergoes as 

 we should if the air were to strike our surface without having been 

 previously prepared by our dress ; the differences of temperature bal- 

 ance themselves within the material we are clothed in, and of which 

 the ends of our cutaneous nerves form no part. Inside our dress we 

 carry the air of the South wherever we may be. Its temperature 

 averages about 75 to 94 Fahr. We live in our dress like an unclothed 

 tribe in a paradisian country, where the air is constantly calm and 

 the temperature 75 to 94. It will be easily understood now why 

 rough, loose textures keep us so warm, while newly-carded cotton- 

 wool does so more than when old and compi-essed ; why tissues of fine 

 tibres and threads make the best material. Fur, of which you know 

 so well the properties, consists of hair and skin. Chemically speak- 

 ing, there is not much difference between skin and hair. In fur the 

 weight or body of the skin is much greater than that of the hair, and 

 still it is essentially the light hair to which the fur owes its warming 

 properties. 



There are some interesting experiments on this point. Krieger 

 observed the flow of heat after covering his cylinders with unshorn 

 and shorn fur. Putting down the loss of heat through the entire fur 

 as 100, he found that it rose to 190 when the same piece of fur was 

 used shorn. A dried skin, you know, is always somewhat porous. 

 When he altered this by giving it a coat of linseed-oil varnish, the 

 loss of heat rose to 258 ; and, when he took a solution of gum-arabic 

 instead, it rose even to 296. 



It has been proved that the living organism, in parting with its 

 heat by radiation and conduction, behaves just like a tin cylinder filled 

 with warm water. It is a yet older observation that furred animals, 

 such as dogs, rabbits, etc., cannot live when they are shorn and their 

 skin varnished or oiled. One used to explain their death by the sup- 

 pression of the evaporation from their skin, but it can be proved that 

 even in a comfortably-warm room these animals literally freeze to 

 death. Krieger sheared a rabbit, after having noted its temperature 



