PRODUCED BY ELECTRO-CHEMICAL ACTION. 101 



charged with vapours, the air no longer retains its morning transpa- 

 rency, and the setting of the sun is attended by a fiery tint which 

 greatly mars the tranquil beauty of the spectacle. It is to those vapours 

 that we are to attribute the inflamed appearance of the sky, because 

 they possess the power of transmitting the tints of the first order, and 

 these are of that fiery cast. Were it not for this circumstance the set- 

 ting of the sun might justly vie with its rising. 



Philosophers had long since settled their opinions as to the co- 

 lours of the sky. These they explained by assigning to the air the 

 propertj' of reflecting the higher colours of the spectrum (violet, indigo, 

 &c.), and that of transmitting the lower, (red, orange, &c.). The ex- 

 planation was correct so far as it went, but to make it complete the 

 exact quality of the tints should be determined by indicating the order 

 to which they belong. It was necessary also to ascertain how light is 

 affected bj^ the presence of vapours. The considerations which we have 

 just stated will perhaps supply both these deficiencies. 



TJdrd and Fourth Rings. — From No. 29 to 38, and from 39 to 44). 



These two rings comprise (if I may use the expression) the richest 

 tints. The tints of the first ring are distinguished by their fiery and 

 metallic appearance ; those of the second by their transparency and 

 vividness ; those of the third and fourth by their intensity, and by the 

 presence of green, which is wanting in the first and second orders. The 

 first appearance of green is in the third order at No. 32: it appears 

 again in the fourth order at No. 41. These two greens differ but little 

 from one another, and are both beautiful in a very high degree : they 

 have a strong resemblance to the green of the emerald. The tints of 

 the third ring do not differ much from those of the fourth : their most 

 marked difference consists in the diminution of transparency observable 

 in passing from the third to the fourth order. 



The colours contained in these two series abound in the three king- 

 doms of nature ; the vegetable kingdom however seems to present them 

 in the greatest proportion. 



The predominant colours in these two parts of the scale are the red, 

 the green, and the yellow-green. There is here, properly speaking, no 

 species of blue, but its absence is counterbalanced by the presence of 

 the green, which is not to be found in the first two rings. It would 

 seem as if the blue belonged peculiarly to the spacious vault of lieaven, 

 and the green to the surface of the earth. They are two dominant 

 colours in nature, but their domains are separated, and the separation 

 seems to me not to be accidental. It was necessary, I suppose, that the 

 atmosphere should be composed of the most subtile particles, in order 

 that they might remain suspended in space ; the earth did not require 

 to be of so delicate a texture. Hence we have two very distinct orders 



