30 THE OCEAK 



with tlie greatest care.* But this transparency does not seem to 

 depend upon the intensity of light received, for in the Arctic Seas 

 floating objects can be perceived at as great depths as in the Ca- 

 ribbean Sea ; and it is indeed in polar latitudes that the eye of man 

 has been able to penetrate to the greatest depth below the surface. 

 According to Scoresby, that conscientious explorer of the polar seas, 

 the sea-bed of the pure waters in these regions is sometimes visible 

 at a depth of 70 fathoms. f It is true that, in consequence of 

 climatic differences and the organic life which depends on them, 

 the bottom of the sea is much more curious to contemplate in 

 the tropical zone than in the neighbourhood of the j^oles. There 

 is nothing more delightful than to sail over one of those seas 

 where, without fear of hidden rocks, one can watch the bed of the 

 sea reveal itself far below the prow of the vessel. Numerous algae, 

 green or rose coloured, wave gracefully below the surface like the 

 grasses of a brook ; the molluscs crawl along the bottom ; crustaceans, 

 fish, star fishes of brilliant colours, and many other animals of strange 

 form, glide slowly or dart like arrows through the blue water, glisten- 

 ing in a thousand changing hues; while the Nemertida and other 

 living ribbons softly unroll their transparent rings. One might fancy 

 oneself suspended above another earth, and floating in an aerial ship. 

 The white foam on the waves raised by the keel of the ship, and the 

 iridescent colours which sparkle in the spray, add fresh charms to 

 this wonderful picture. 



Even when the bed of the sea is not distinctly visible, it does not 

 fail to reveal itself by the peculiar tint it imparts to the water. In 

 general the colour of the sea is lighter near the coasts, and even at 

 a depth of above 100 to 150 fathoms, a paler shade of the water at 

 times makes known to the practised eye of the mariner the relative 

 proximity of the bottom. Not far from the coasts of Peru, de Tessau 

 perceived that the sea had suddenly assumed a tint of dark olive- 

 green, and when he caused a sounding to be taken, it was found 

 that the mud at the bottom was precisely of this colour. Numerous 

 navigators have afiirmed that in one part of the Lagullas bank, where 

 the mass of water is above 1 00 fathoms deep, the water passes sud- 

 denly from blue to a greenish colour. J Lastly, off" Loango, the 

 water is always brown, similar to that of the bottom, which Tuckey 

 has found to be of an intense red. Is, then, this colouring owing to 



* Cialdi, Sul moto ondoso del mare, p. 284. 



t Arctic Regiom. See also the Notice of Arago, CFAivres completes, t. ix. 



X Arago, ibid. 



