16 INTRODUCTION. 



by tlieir great beauty, that He issues, so to speak, a new law 

 of nature. Looking at land-plants, we would say that it is 

 a law of nature (that is, the appointment of God) that the 

 full light of the sun is necessary to bring forth their beau- 

 tiful tints. Shut out almost all the light of the sun from a 

 rose-bud coming into flower, and, if it expand at all, how 

 pale and sickly does it look, — 



" Like saddest portrait, painted after death." 



Exclude altogether the enlivening sunbeams from plants of 

 the sweetest verdure, and they become quite blanched, as 

 if white robes were with them, as among some nations, the 

 weeds of woe. How difi'erent is the case with marine 

 plants ! Humboldt mentions a Fnciis of a fine grass-green 

 colour, brought up from the great depth of 192 feet, where 

 it had vegetated, though the light that reached it at that 

 depth could have been equal only to half the light of an 

 ordinary candle; and according to his own experiments, 

 common garden-cresses exposed during vegetation to the 

 brilliant light of two Argand lamps, acquired only a slight 

 tint of green. Sea-plants of a red colour, it is well known, 

 acquire their richest red in the deepest water ; and at depths 

 to which, it is known, the rays of the sun do not reach, 

 there are many species of Alga? of different hues, as fully 



