The Colour of the Sea 127 



Beyond this depth it became indistinct, and became invisible 

 at about 27 fathoms, but this was due mainly to its smallness 

 and to its want of steadiness, being attached to the boat, 

 which rose and fell with the swell. At 25 fathoms the plate 

 had a pale ultramarine colour, and its edges were sharply 

 denned. These separated the column of water, into which 

 I looked through the water-glass, into a central column of 

 rectangular section having a depth of 25 fathoms, and into 

 a column, surrounding and contiguous with it, which had 

 a depth many times greater. These columns, being juxtaposed, 

 placed in the way most favourable for the comparison 

 of their colours. The colour of the central column, 25 fathoms 

 in length, was a pure but pale ultramarine ; that of the external 

 and uninterrupted column through which the whole unabsorbed 

 and undissipated part of the sunlight which had penetrated 

 into the water returned to the surface was of the same tone, 

 but of many times greater intensity. Assuming the intensitv 

 of the colour to be proportional to the length of the column 

 of water traversed by the light, it is to be concluded that the 

 length of the uninterrupted column which transmitted the 

 more intense colour was many times greater than 25 fathoms. 

 It must be noted that the glass plate forming the bottom 

 of the small tub, which is called a "water-glass," was during 

 the observation completely protected from direct sky-light 



iv head and the brim of the panama hat whit h, at that 

 time. I alwav- wore when exposed to the sun. 



It has already been said that water of as pin- 



iat of the Antarctic occurs in other and warmer districts 



of the ocean. My attention was first directed to this during 



rise of the "Dada," which, although it occupied no 



than three week-, marks an epoch in deep-sea research. 



iort account of it is given in a paper by me "On Oc< 

 discovered in s.s. "Dacia" in October, 1883" and 

 (tcdings of the Royal Society of Edinburgh, 

 1885, xiii. j>. 748. Perhaps the most remarkable of these 



ils was the one which was named the "Coral Patch," 



n 57' \V., t U h. 



.th th.it <>f the tid.il curn-nt- in the open ocean (Proc. 



