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distinguish between the effects of those simultaneous operations, and 

 of ascertaining their relative intensities. A hot body, A for instance, 

 heats a neighbouring colder body B, by its calorific radiations ; but 

 B emits at the same tune frigorific radiations, which contribute to 

 lower the temperature of A ; nor is it clear that both these bodies, 

 especially if, they have polished surfaces, will not reciprocally, and 

 perhaps repeatedly, reflect those incident rays, and that those rays 

 will not be refracted by the media through which they pass, and be 

 concentrated or expanded by the shapes of the reflecting surfaces, 

 and thus create a combination of effects, which it will require much 

 labour and ingenuity to unravel. 



As it is impossible for us within our narrow limits to do justice to 

 the connected series of observations and arguments here adduced, we 

 shall refer those who wish for more ample information on the subject 

 to the paper itself; and this the rather, that we may dwell more 

 largely upon the practical uses that may be derived from a knowledge 

 of the facts which the author now considers as fully established. 



In all cases where it is intended to preserve the heat of any sub- 

 stance which is confined in a metallic vessel, it will greatly contribute 

 to that end if the external surface of that vessel be kept very clean 

 and bright; but if the object be to cool anything quickly in such a 

 vessel, its external surface should be painted, or coloured with some 

 of those substances which have been found to emit calorific radiations 

 in abundance. Hence the sides of kitchen utensils should be kept 

 bright, in order to confine the heat ; while their bottoms should be 

 blackened, in order that their contents may be made to boil sooner, 

 and with a less expense of fuel. 



Brewers, it seems, are mistaken when they employ broad shallow 

 vessels, or flats, as they call them, of metal for cooling their wort. 

 Wooden flats, it appears, ought in every respect to have the pre- 

 ference. 



In all cases when metallic tubes, filled with steam, are used for 

 warming rooms or hot-houses, the external surface of those tubes 

 should be painted, or covered with some substance which facilitates 

 the emission of calorific rays. Where, on the other hand, tubes are 

 intended to convey hot steam from one place to another, they should 

 be kept very clean and bright. This applies also to the cylinders of 

 steam-engines, and the principal tubes used in that machine. 



Gardeners should advert to the circumstance, that if walls painted 

 black acquire heat faster when exposed to the sun's direct rays, they 

 likewise cool much faster during the night, and in the shade when 

 the weather is cold. 



Black cloths are known to be very w r arm in the sun ; but they are 

 far from being so in the shade, especially in cold weather, when the 

 temperature of the air is below that of the surface of the skin. 



It having been shown that the warmth of clothing depends much 

 on the polish of the surface of the substance of which it is made, we 

 may conclude that in choosing the colour of our winter garments, 

 those dyes should be avoided which tend most to destroy that polish. 



