182 FRAGMENTS OF SCIENCE 



Portsmoutli : the other carrisd out in the laboratory of the 

 Royal 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 re- 

 garding 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-color corresponding to 

 the various specimens ascertained. The home observa* 

 tions, therefore, must have been perfectly unbiased, and 

 they clearly establish the association of the green color with 

 fine suspended matter, and of the ultramarine color, 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 preliminary re- 

 mark or two will clear our way toward an explanation. 

 Color resides in white light, appearing when any constit- 

 uent of the white light is withdrawn. The hue of a pur- 

 ple liquid, for example, is immediately accounted for by 

 its action on a spectrum. It cuts out the yellow and 

 green, and allows the red and blue to pass through. The 

 blending of these two colors produces the purple. But 

 while such a liquid attacks with special energy the yellow 

 and green, it enfeebles the whole spectrum. By increas- 



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

 tains the following reference to this point: **! have never seen the Lake of 

 Cteneva, but I thought of the brilliant dazzling dark blue of the mid- Atlantic 

 under the sunlight, and its black-blue under cloud, both so solid that one might 

 leap off the sponson on to it without fear; this was to me the most wonderful 

 thing whicli I saw on my voyages to and from the West Indies." 



