394 TUIL BOTTOM OF THE SEA. 



digious growth results in the formation of submarine 

 prairies, which serve as a retreat for thousands of 

 animals. 



The tangled roots of the algaj serve to bind together 

 and strengthen the loose bottom of the sea, and in 

 some cases near the coast favour the extension of 

 the land into the sea — thus tliemselves assisting 

 to diminish the extent of the domain they inhabit. 



In the middle of oceans, more particularly in the 

 Atlantic, enormous quantities of seaweed are met 

 with, which have no hold on the bottom of the sea, 

 in these parts of great depth. The quantities of 

 these plants are so enormous, that the first sailors 

 who met with them mistook the appearance they 

 presented for dry land, and were terrified to find 

 their vessels becoming more and more entangled in 

 the weeds which thus hindered their progress. It is 

 now known that these immense accumulations of 

 seaweed are due to a species of circular current in 

 the vast basin of the sea, towards the centre of which 

 all the loose floating debris detached from the coasts 

 tends to converge. 



A tree, the RJiizojpJiora mangle (mangrove), has a 

 remarkable influence on the extension of the coasts 

 of Guiana, uniting its action with that of the equa- 

 torial current, which, as we have already seen, 

 transports the delta of the Amazon, fragment by 



