RADIATION OF HEAT. 79 



A remarkable change takes place in the character of 

 heat in being reflected from material substances. In 

 nature we often see this fact curiously illustrated. Snow 

 which lies near the trunks of trees or wooden poles 

 melts much quicker than that which is at a distance 

 from them, the sun shining equally on both the lique- 

 faction commencing on the side facing the sun, and 

 gradually extending. We see, therefore, that the direct 

 rays of solar heat produce less effect upon the snow than 

 those which are radiated from coloured surfaces. By 

 numerous experiments, it has been shown that these se- 

 condary radiations are more abundantly absorbed by snow 

 or white bodies than the direct solar rays themselves. 

 Here is one of the many very curious evidences, which 

 science lays open to us, of the intimate connection be- 

 tween the most ethereal and the grosser forms of matter. 

 Heat, by touching the earth, becomes more earth-like. 

 The subtile principle which, like the spirit of supersti- 

 tion, has the power of passing, unfelt, through the 

 crystal mass, is robbed of its might by embracing the 

 things of earth ; and although it still retains the evidences 

 of its refined origin, its movements are shackled as by a 

 clog of clay, and its wings are heavy with the dust of 

 this rolling ball. It has, however, acquired new pro- 

 perties, which fit it for the requirements of creation, and 

 by which its great tasks are facilitated. Matter and 

 heat unite in a common bond, and, harmoniously pur- 

 suing the necessities of some universal law, the result 

 is the extension of beautiful forms in every kingdom of 

 nature. 



An easy experiment pleasingly illustrates this remark- 

 able change. If a blackened card is placed upon snow 

 or ice in the sunshiue, the frozen mass underneath it will 

 be gradually thawed, and the card sink into it, while 

 that by which it is surrounded, although exposed to the 

 full power of solar heat, is but Little disturbed. If, how- 



