PHYSICAL AND LITERARY. ^g 



green rays, appear almoft intirely white 

 when viewed from the earth ? May not this 

 be accounted for, in the fame manner as the 

 change of colour obfcrvable in earthly ob- 

 je6ls feen thro' a great trad: of the atmo- 

 fphere ? A mountain covered with the 

 frefheft verdure^ tit the diftance of twelve of 

 fifteen miles, looks blueifli j and at twenty- 

 or thirty, efpecially if the air be thickened,- 

 degenerates into a dim white, fo that one' 

 can hardly diftinguifh it from the clouds that 

 i(k.irt the horizon; With refped; to the pri- 

 mary planets, .it may be likeways anfwered, 

 that perhaps we fee them chiefly by light 

 refledted from the air and vapours that fur-' 

 round them. 



" QuER. XIII. Why is it fo hard to diftiii-- 

 guifh green bodies from blue by candle-' 

 light ? 



QuER. XIV. Whence proceeds the blue- 

 iiefs of the fky ? Since it is certairv that no' 

 body affumes any particular colour, but be^'' 

 eaufe it refieds one fort of rays more abun-' 

 dantly than the reft ; and fince it cannot be 

 fuppofed that the cbnftituent parts of -ptfre' 

 air are grofs enough to feparate any colours 

 of themfelves j mqft we not conclude, with 

 Vol, II. K Sir 



