46 Of the Management of Fire 



But among all the various substances of which cover- 

 ings may be formed for confining heat, none can be 

 employed with greater advantage than common atmos- 

 pheric air. It is what nature employs for that purpose ; 

 and we cannot do better than to imitate her. 



The warmth of the wool and fur of beasts, and of the 

 feathers of birds, is undoubtedly owing to the air in their 

 interstices ; which air, being strongly attracted by these 

 substances, is confined, and forms a barrier which not 

 only prevents the cold winds from approaching the body 

 of the animal, but which opposes an almost insurmount- 

 able obstacle to the escape of the heat of the animal 

 into the atmosphere. And in the same manner the air 

 in snow serves to preserve the heat of the earth in win- 

 ter. The warmth of all kinds of artificial clothing may 

 be shown to depend on the same cause ; and were this 

 circumstance more generally known, and more attended 

 to, very important improvements in the management of 

 heat could not fail to result from it. A great part of our 

 lives is spent in guarding ourselves against the extremes 

 of heat and of cold, and in operations in which the use 

 of fire is indispensable'; and yet how little progress has 

 been made in that most useful and most important of 

 the arts, the management of heat ! 



Double windows have been in use many years in most 

 of the northern parts of Europe, and their great utility, 

 in rendering the houses furnished with them warm and 

 comfortable in winter, is universally acknowledged ; but 

 I have never heard that anybody has thought of em- 

 ploying them in hot countries to keep their apartments 

 cool in summer ; yet how easy and natural is this appli- 

 cation of so simple and so useful an invention ! If a 

 double window can prevent the heat which is in a room 



