RELATIONS OF THE AIR TO OUR CLOTHING. 667 



but the few experiments known to me entirely run counter to our ac- 

 cepted ideas. 



Krieger experimented on cylinders filled with warm water, by sur- 

 rounding them tightly with single or double textures. As the loss by 

 radiation is the same in both cases, any difference must result from 

 difference of conductive power in the coverings of the cylinders; but 

 the results were, for the most part, surprisingly small. The following 

 numbers represent the proportions of loss of heat through double 

 tight-fitting coverings in comparison to single ones ; the losses through 

 the single ones being taken as 100, they were, through- 

 Double thin silk 9 ^ 



" Gutta-percha 96 



" Shirtings 95 



" Fine linen 95 



" Stoutsilk 94 



" Thick home-spun linen 91 



" Chamois-leather 88-90 



" Flannel 86 



" Summer buckskin 88 



" Winter buckskin 74-84 



" Double stuffs 69-75 



The whole question is certainly not exhausted by these experiments, 

 but one thing becomes evident by them, that it is not the substance 

 and its weight, but the texture and the volume, which are the principal 

 causes of the difference. Thin and stout silks, fine and stout linen, are 

 nearly equal in substance, and equal sizes of them are not so very 

 different in weight ; it is their different heat-conducting power which 

 causes the difference of the loss, and this is, even through two layers of 

 them, not as much as ten per cent, smaller than through a single one. 



By other experiments one can demonstrate that, by changing the 

 shape and volume of the same substance, great changes of heat-loss 

 can be produced, although the substance and its weight remain the 

 same. If you cover the tin cylinder, previously filled with warm 

 water, with common wadding, and observe the falling of the im- 

 mersed thermometer, you will be astonished to see how rapidly the 

 fall goes on, as soon as you compress the wadding firmly and diminish 

 its volume : the outward flow of the heat increases by forty per cent.. 

 The same, you know, is the case, when a wadded garment is worn out ; 

 the quantity of the wadding is the same, but its volume and its elas- 

 ticity have undergone a change, and you will find it considerably less 

 protecting. 



This observation leads to another instructive experiment, relating 

 to the influence of double layers of material. If the first layer only 

 is tightly drawn over the warm cylinder, and a free space of one-third 

 to one-half an inch between it and the second, which may be compared 

 to a comfortably-fitting garment, the second layer very considerably 

 lessens the outward flow of the heat. The amount due to conduction 



