BOOK IV. 



APPLICATIONS OF THE PHENOMENA ANt) THE 

 LAWS OF HEAT. 



CHAPTER I. 



THE ART OF WARMING. 



1. ANCIENT METHODS OF WARMING. 



OF all the varying conditions which are hurtful to our health, or 

 restrict us, to a certain degree, in the full use of our physical and 

 intellectual faculties, sudden changes of temperature and the ex- 

 tremes of heat and cold are among those which affect us the most, 

 and against which it is the most necessary for us to be on our guard. 

 The regions of the earth, where reigns, as the old phrase runs, a per- 

 petual spring, are few, and but little inhabited. Even in the temperate 

 zones there is a wide interval between the summer's heat and the 

 winter's cold. In proportion, too, as civilisation embraces larger and 

 larger areas both in the New and the Old World, so voyages multiply, 

 fresh countries are colonised, and man is forced to live in places 

 where the extremes of temperature, unless their effects are overcome, 

 would render his acclimatisation difficult, or at all events dangerous 

 to his health. Hence the need of combating these effects, whether 

 dangerous or simply disagreeable, by appropriate methods, and 

 of regulating the use of the latter by the laws of physics and 

 hygiene. 



These methods are of various kinds. They may have reference 

 to our houses, our clothes, or even to our meat and drink ; and it is 



