170 FRAGMENTS OF SCIENCE. 



water. A second specimen of water, taken from the 

 Bay of Biscay, held in suspension fine particles of a 

 peculiar kind; the size of them was such as to render 

 the water richly iridescent. It showed itself green, 

 blue, or salmon-coloured, according to the direction of 

 the line of vision. Finally, we come to our last two 

 bottles, the one taken opposite St. Catherine's light- 

 house, in the Isle of Wight, the other at Spithead. The 

 sea at both these places was green, and both specimens, 

 as might be expected, were pronounced by the home 

 examination to be thick with suspended matter. 



Two distinct series of observations are here referred 

 to the one consisting of direct observations of the 

 colour of the sea, conducted during the voyage from 

 Gibraltar to Portsmouth: the other carried out in the 

 laboratory of the Eoyal Institution. And here it is to 

 be noted that in the home examination I never knew 

 what water was placed in my hands. The labels, with 

 the names of the localities written upon them, had 

 been tied up, all information regarding the source of 

 the water being thus held back. The bottles were sim- 

 ply numbered, and not till all of them had been ex- 

 amined, and described, were the labels opened, and the 

 locality and sea-colour corresponding to the various 

 specimens ascertained. The home observations, there- 

 fore, must have been perfectly unbiassed, and they 

 clearly establish the association of the green colour 

 with fine suspended matter, and of the ultramarine 

 colour, and more especially of the black-indigo hue of 

 the Atlantic, with the comparative absence of such 

 matter. 



So much for mere observation; but what is the 

 cause of the dark hue of the deep ocean? * A prelimi- 



* A note, written to me on October 22, by my friend Canon 

 Kingsley, contains the following reference to this point : ' I have 



