16 DISCOLOURED SEA. [ HAP. I. 



In the sea around Tierra del Fuego, and at no great distance 

 from the land, I have seen narrow lines of water of a bright red 

 colour, from the number of Crustacea, which somewhat resemble in 

 form large prawns. The sealers call them whale-food. Whether 

 whales feed on them I do not know ; but terns, cormorants, and 

 immense herds of great un wieldly seals derive, on some parts of 

 the coast, their chief sustenance from these swimming crabs. 

 Seamen invariably attribute the discoloration of the water to 

 spawn; but I found this to be the case only on one occasion. At 

 the distance of several leagues from the Archipelago of the Gala- 

 pagos, the ship sailed through three strips of a dark yellowish, or 

 mud-like water ; these strips were some miles long, but only a few 

 yards wide, and they were separated from the surrounding water 

 by a sinuous yet distinct margin. The colour was caused by little 

 gelatinous balls, about the fifth of an inch in diameter, in which 

 numerous minute spherical ovules were imbedded : they were of 

 two distinct kinds, one being of a reddish colour and of a different 

 shape from the other. I cannot form a conjecture as to what two 

 kinds of animals these belonged. Captain Colnett remarks, that 

 this appearance is very common among the Galapagos Islands, and 

 that the directions of the bands indicate that of the currents ; in 

 the described case, however, the line was caused by the wind. 

 The only other appearance which I have to notice, is a thin oily 

 coat on the water which displays iridescent colours. I saw a 

 considerable tract of the ocean thus covered on the coast of Brazil ; 

 the seamen attributed it to the putrefying carcass of some whale, 

 which probably was floating at no great distance. I do not here 

 mention the minute gelatinous particles, hereafter to be referred 

 to, which are frequently dispersed throughout the water, for they 

 are not sufficiently abundant to create any change of colour. 



There are two circumstances in the above accounts which appear 

 remarkable : first, how do the various bodies which form the bauds 

 with defined edges keep together ? In the case of the prawn-like 

 crabs, their movements were as co-instantaneous as in a regiment of 

 soldiers'; Jbut this cannot happen from anything like voluntary 

 action with the ovules, or the confervae, nor is it probable among the 

 infusoria. Secondly, what causes the length and narrowness of the 

 bands? The appearance so much resembles that which may be 

 seen in every torrent, where the stream uncoils into long streaks 

 the froth collected in the eddies, that I must attribute the effect to 



