THE MOUNTAIN. 



boy, however, gave it as his opinion that we had 

 heard the distant note of the nobler bird; and 

 presently, to my great gratification, a pair of these 

 lords of the feathered creation rose from behind a 

 mountain-peak, at the distance of about a quarter 

 of a mile from us. They soared about for a long 

 time, occasionally uttering their short and very 

 peculiar cry, and alighting among the rocks, but 

 never came near enough to allow us to have a good 

 view of them. 



The summits of lofty mountains are covered 

 with snow all the year round. In all elevated 

 lands, also, the temperature is much beneath that 

 of the adjoining low countries. This difference is 

 partly owing to the constant exposure of the 

 former to cold winds, from which the plains are 

 more or less protected ; but chiefly to what is 

 called the " radiation of heat." I ought, perhaps, 

 to explain what I mean by these words. 



All bodies, whatever their temperature may be, 

 that is to say, whether we should call them 

 warm or cold, have a natural tendency to part 

 with their heat, which, in conformity with this 

 law, is constantly proceeding from all parts of their 

 surface, and in all directions, in straight lines. 

 For example, if we were to suspend a mass of hot 

 iron in the centre of a room, it would gradually 

 cool ; that is, it would radiate its heat in all direc- 

 tions, until the floor, the ceiling, and the sides of 

 the room had all attained the same temperature 

 with itself. The various parts of the room would 

 also radiate heat at the same time, though in so 

 small a proportion to that received from the iron 

 that it would be scarcely perceptible. 



