204 XOVUM ORGANUM 



are grounded chiefly upon this, that the moon reflects the 

 sun s rajs, and that light does not appear capable of being 

 reflected except by solids. The instances of the cross will 

 therefore (if any) be such as to exhibit reflection by a rare 

 body, such as flame, if it be but sufficietly dense. Now, 

 certainly, one of the reasons of twilight is the reflection 63 

 of the rays of the sun by the upper part of the atmosphere. 

 We see the sun s rays also reflected on fine evenings by 

 streaks of moist clouds, with a splendor not less, but per 

 haps more bright and glorious than that reflected from the 

 body of the moon, and yet it is not clear that those clouds 

 have formed into a dense body of water. We see, also, that 

 the dark air behind the windows at night reflects the light 

 of a candle in the same manner as a dense body would do. 64 

 The experiment should also be made of causing the sun s 

 rays to fall through a hole upon some dark and bluish 

 flame. The unconfined rays of the sun, when falling on 

 faint flames, do certainly appear to deaden them, and render 

 them more like white smoke than flames. These are the 

 only instances which occur at present of the nature of those 

 of the cross, and better perhaps can be found. But it must 

 always be observed that reflection is not to be expected 

 from flame, unless it be of some depth, for otherwise it be- 



law, however, has not only established its solidity, but its density and weight. 

 A sufficient proof of the former is afforded by the attraction of the sea, and the 

 moon s motion round the earth. Ed. 



63 Rather the refraction ; the sky or air, however, reflects the blue rays 

 of light, 



64 The polished surface of the glass causes the reflection in this case, and 

 not the air; and a hat or other black surface put behind the window in the 

 daytime will enable the glass to reflect distinctly for the same reason, namely, 

 that the reflected rays are not mixed and confused with those transmitted from 

 the other side of the window. 



