222 FKAGMENTS OF SCIENCE. 



greatly augmented purity of the 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 lighthouse, in the Isle of Wight, 

 the other at Spifchead. 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 simply 

 numbered, and not till all of them had been examined, 

 and described, were the labels opened, and the locality 

 and sea-colour corresponding to the various specimens 

 ascertained. The home observations, therefore, 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 ? l A prelimi- 



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

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



