128 Inquiry concerning the Nature of Heat, 



bright. The expense of this covering would, I am con- 

 fident, be amply repaid by the saving of heat and fuel 

 which would result from it. 



If garden walls painted black acquire heat faster when 

 exposed to the sun's direct rays than when they are not 

 so painted, they will likewise cool faster during the 

 night ; and gardeners must be best able to determine 

 whether these rapid changes of temperature are, or are 

 not, favourable to fruit-trees. 



Black clothes are well known to be very warm in the 

 sun ; but they are far from being so in the shade, and 

 especially in cold weather. No coloured clothing is so 

 cold as black when the temperature of the air is below 

 that of the surface of the skin, and when the body is 

 not exposed to the action of calorific rays from other 

 substances. 



It has been shown that the warmth of clothing de- 

 pends much on the polish of the surface of the substance 

 of which it is made; and hence we may conclude that, 

 in choosing the colour of our winter garments, those 

 dyes should be avoided which tend most to destroy that 

 polish ; and, as a white surface reflects more light than 

 an equal surface, equally polished, of any other colour, 

 there is much reason to think that white garments are 

 warmer than any other in cold weather. They are uni- 

 versally considered as the coolest that can be worn in 

 very hot weather, and especially when a person is ex- 

 posed to the direct rays of the sun ; and if they are well 

 calculated to reflect calorific rays in summer, they must 

 be equally well calculated to reflect those frigorific rays 

 by which we are cooled and annoyed in winter. 



I have found, by direct and decisive experiments (of 

 which an account will hereafter be given to this Soci- 



