96 FRAGMENTS OF SCIENCE 



halted at facts, however practically useful, and neglected 

 the laws which accompany and rule the phenomena. Let 

 us endeavor then to extract from the experiment of Frank- 

 lin all that it can yield, calling to our aid the knowledge 

 which our predecessors have already stored. Let us im- 

 agine two pieces of cloth of the same texture, the one black 

 and the other white, placed upon sunned snow. Fixing 

 our attention on the white piece, let us inquire whether 

 there is any reason to expect that it will sink in the snow 

 at all. There is knowledge at hand which enables us to 

 reply at once in the negative. There is, on the contrary, 

 reason to expect that, after a sufficient exposure, the bit 

 of cloth will be found on an eminence instead of in a hol- 

 low; that, instead of a depression, we shall have a relative 

 elevation of the bit of cloth. For, as regards the luminous 

 rays of the sun, the cloth and the snow are alike power- 

 less; the one cannot be warmed, nor the other melted, by 

 such rays. The cloth is white and the snow is white, be- 

 cause their confusedly mingled fibres and particles are 

 incompetent to absorb the luminous rays. Whether, then, 

 the cloth will sink or not depends entirely upon the dark 

 rays of the sun. Now, the substance which absorbs these 

 dark rays with the greatest avidity is ice or snow, which 

 is merely ice in powder. Hence, a less amount of heat 

 will be lodged in the cloth than in the surrounding snow. 

 The cloth must therefore act as a shield to the snow on 

 which it rests; and, in consequence of the more rapid 

 fusion of the exposed snow, its shield must, in due time, 

 be left behind, perched upon an eminence like a glacier- 

 table. 



But though the snow transcends the cloth, both as a 

 radiator and absorber, it does not much transcend it. 



