THE EARTH. 211 



Water may be reduced to a fluid every vvay resembling air, by 

 heat; which, by cold, becomes water again. Everything we 

 see gives off its parts to the air, and has a little floating atmo- 

 sphere of its own round it. The rose is encompassed with a 

 sphere of its own odorous particles ; while the night-shade in- 

 fects the air with a scent of a more ungrateful nature. The 

 perfume ot musk flies off in such abundance, that the quantity 

 rpmaining becomes sensibly lighter by the loss. A thousand 

 substances that escape all our senses we know to be there ; the 

 powerfid emanations of the load-stone, the effluvia of electricity, 

 the rays of light, and the insinuations of fire. Such are the 

 various substances through which we move, and which we are 

 constantly taking in at every pore, and returning again with im- 

 peiceptible discharge ! 



This great solution, or mixture of all earthly bodies, is con- 

 tinually operating upon itself ; which, perhaps, may be the cause 

 of its unceasing motion ; but it operates still more visibly upon 

 such grosser substances as are exposed to its influence ; for 



the Htmospliere, and the resulting colour will be either orange or red, ac- 

 -ordiiig to the quantity of the least refrangible rays that have been stopt in 

 t'.ieir course. Hence the rich and brilliant hue with which nature is gilded 

 by the setting sun ; hence the glowing red which tinges the morning and 

 evening clouds ; and hence the sober purple of twilight which they assuma 

 when their ruddy glare is tempered by the reflected azure of the sky. 



We have already seen, that the redrays penetrate through the atmosphere, 

 while the blue rays, less able to surmount the resistance which they meet, are 

 reflected or absorbed in their passage. It is to this cause that we must ascribe 

 the colour of the sky, and the bright azure which tinges the mountains of 

 the distant landscape. As we ascend in the atmosphere, the deepness of 

 the blue tinge gi-adually dies away ; and to the aeronaut who has soared 

 above the denser strata, or to the traveller who has ascended the Alps or the 

 Andes, the sky appears of a deep black, while the blue rays find a ready 

 passage through the attenuated strata of the atmosphere. It is owing to the 

 same cause that the diver at the bottom of the sea, is surrounded with the 

 red light which has pierced through the superincumbent fluid, and that the 

 blue rays are reflected from the surface of tlie ocean. Were it not for tlie 

 reflecting power of the air, and of the clouds which float in the lower re- 

 gious of the atmosphere, we should be involved in total darkness by the set. 

 ting of the snn, and by every cloud that passes over his disc. It is to the 

 multiplied reflections which the light of the sun suffers in the atmosphere, 

 that we are indebted for the light of day, when the earth is enveloped with 

 impenetrable clouds. From the same cause arises the sober hue of the morn, 

 ing and evening twilight, which increases as we recede from the equaloi 

 till it blesses with perpotual day the inhabitants of the pt.«lar regions. 



