The Colour of the Sea 



diatoms themselves. Water belonging to this type of colour 

 is not confined to polar latitudes; it is met with in a certain 

 class of homologous districts of the warmer ocean, in tropical 

 and even in equatorial latitudes. 



\\ 'hi 'ii \ve quit the edge of the polar ice and steer equator- 

 's, the surface water assumes a pronounced indigo colour, 

 and this persists until we pass the fortieth parallel. If we 

 from the equator and sail polewards, the colour of the 

 surface water persists as a pure and brilliant ultramarine until 

 the thirtieth parallel is passed. The passage from the ultra- 

 marine to the indigo, and vice versa, is usually very rapid, 

 and the area of mixture is restricted. No one who has once 

 sailed in the ultramarine waters of the intratropical ocean 

 and has observed, as well as seen, its colour, can ever mistake 

 any other colour for it. If he has doubt as to whether the 

 r through which he is passing is ultramarine or not, he 

 may be sure that it is not. The ultramarine and the indigo 

 are the two great colour-types to which the mass of the surface 

 r of the deep sea belongs, and, with the olive-green, they 

 make the three fundamental colour-types which are required, 

 and are sufficient for the adequate logging of the colour of the 

 -urface water of the ocean. 



water of the Mediterranean belongs to the ultramarine 

 but it always appears to me to have a harder tone than 

 the soft and brilliant ultramarine of the intratropical ocean. 

 With regard to the method of judging the colour of the 

 much unnecessary difficulty is made. The first pre- 

 ion to be observed is to take up a position where the 

 i test amount of light can reach the eye after passing through 

 and the smallest amount after beint: reflected 

 fron face. There is generally little difficult v in accom- 



thi^ <n OIK -j.lr or tin- >th r of the ship and by looking 

 --ililr v -i tie, illy into the water. 

 Dger," lik. ntln r mm of \var of her dato, was 

 fully rigged, and built for s.iilim; fcf \v< 11 as for steaming. 

 \Vh.n uii'lri ^>\\ the propcll* r -a uses a certain amount of 

 to reme<lv thi^ shr \va< tittnl with a "screw- 

 in t< \vhieh the propeller could be hoisted out of tho 



