USE OF THE TAILS OF FISH. 211 



nated cetacea, which require to rise frequently to 

 the surface of the water for the purpose of respi- 

 ration, have tails lying horizontally with the water 

 and not perpendicularly in it. This wise provision 

 of nature is to enable them to rise and sink in the 

 water with greater facility. They have only to 

 strike their flat tails against the waters in the 

 depth of ocean, and straightway they are sent 

 many fathoms upwards ; a contrary caudal action 

 will send them down into the deeps again. If the 

 whale were not provided with the flat or horizontal 

 tail it would die of suffocation, as it would then be 

 unable to lift into vital air his huge carcase from 

 the dark unfathomed caves in which he cannot long 

 rest for want of ventilation. The dorsal, pectoral, 

 and ventral fins of salmon are the agents by which 

 they rise and sink in the water. By the agency, 

 in great part, of the caudal fin or tail, they are 

 enabled to propel themselves in any horizontal 

 direction. 



A salmon cannot spring far out of the water 

 unless it be deep, but I do not think it need be 

 very deep. In making its spring it first sinks 

 rapidly by upward action of the fins, and then 

 suddenly reversing their action, and finding a 

 point cVappui in the volume of water under it 

 and bringing the saltant powers of its muscles 



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