130 THE MOUNTAIN. 



This property, I have said, is common to all 

 bodies. But it is evident that the greater the 

 bulk of a body when compared to the surface 

 which it presents, the less heat it radiates, or, in 

 other words, the longer it takes to cool. For in- 

 stance, a spherical mass of iron will retain its heat 

 longer than the same quantity of metal would if 

 beaten out into a thin plate; so, an irregular 

 body, a cinder, for instance, taken from the fire 

 cools first at the extremities or projecting points ; 

 and again, to adduce an example, which I dare 

 say will make you smile, if you go into the open 

 air in a cold day, the parts of your face which 

 suffer most from the cold will be your nose and 

 your chin. Now, mountains are to the mass of 

 the earth what your nose and your chin are to 

 your face. They radiate the heat which they 

 have received from the sun long before the parts 

 which are nearer to the centre of the globe, and 

 become so cold that snow falling on them does not 

 thaw, but remains without diminution from year 

 to year. A thermometer suspended only a few 

 feet from the earth's surface indicates a tempera- 

 ture sensibly lower than it would if placed on the 

 ground ; because, in the latter case, it receives heat 

 from the earth by radiation in a greater degree 

 than when placed at a distance from it. 



Another exemplification of the same law is af- 

 forded by the phenomenon of Dew. Walk through 

 a meadow early in the morning in winter after a 

 clear night, and you will see every blade of grass 

 fringed with sparkling crystals of hoar-frost, while 

 the pathway is not in the least affected. Take the 

 same walk on a summer's morning, and, if the sky 

 has been cloudless during the night, every leaf, 



