390 EAMBLES OP A NATUEALIST. [Oh. XXII. 



as such, in sufficient quantities, absorbs the red and yellow 

 with their compounds, rejecting the blue and violet for the 

 benefit of our eyes. 



Father Secchi of Eome, in examining the water of the sea, 

 found that the spectrum of its colour lost its red. rays first, 

 and at a slight depth ; after which, as the depth increased, 

 the yellow and green rays successively disappeared to a 

 great extent, and the water assumed its violet-blue tint. 

 And in some researches which he has lately been making 

 upon the colour of light transmitted through masses of ice, 

 he finds that the red rays are very faiat, being mostly ab- 

 sorbed, while the richest blue was transmitted, so that in a 

 grotto of ice the fleSh-tints of the human face assumed 

 that ghastly appearance which is seen when a homogeneous 

 blue light is burniug ; and he comes to the conclusion that 

 the true colour of water is blue, mixed with violet. 



