LECTURE II. 103 



extended scale, solicitously enquiring into 

 all those particulars which adapt these 

 animals to the peculiar situation they 

 occupy in the scale of existence. The 

 horizontal direction of the tail, so different 

 from that of fish, and the cause of the pe- 

 culiar strength of the flexor muscles, ana- 

 logous, as he says, to the lumbar muscles 

 of anitnals, is shewn to be calculated to 

 raise the most prominent part of the ani- 

 mal, where the blow-hole is placed, above 

 the surface of the water for respiration ; 

 whilst the horizontal motions of the tail 

 are equally adapted to depress it to the 

 depths of the ocean in search of food. 

 The motions of the tail cause these animals 

 to move up and down in a curvilinear di- 

 rection, which makes them appear hump- 

 backed, and thus the dolphin is generally 

 represented. We see this in porpoises when 

 they swim slowly and near shore, alternately 

 respiring and grubbing along the bottom. 

 Yet these creatures can, with their powerful 

 tails, scull themselves forwards in a strait 

 direction with surprising speed, passing a 

 ship whilst she is going at the rate of ten 



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