158 LECTURE XL 



whole surface by very numerous, deeply- impress- 

 ed, obliquely-descending furrows ; and the keel or 

 bottom is tuberculated along each side by the pro- 

 jecting tips of the furrowed part of the shell. This 

 shell, with its inhabiting animal, sailing along the 

 surface in fine weather, has from very remote 

 times attracted the admiration of mankind, and 

 has been celebrated as having given the first hint 

 for the practice of navigation, as if man, with all 

 his powers of mind, was unable to conceive the 

 possibility of swimming or sailing in a boat upon 

 the water, without first receiving a hint from the 

 inhabitant of a shell ! This is the species to which 

 the well-known lines of Pope allude, and which 

 have been so often quoted on the subject, that not- 

 withstanding their real beauty, they may be consi- 

 dered as almost vulgarized by frequent repetition* 



" Learn of the little Nautilus to sail, 



t! Spread the thin oar, and catch the rising gale.'' 



/ 



As the animal which thus sails in the shell called 



the Paper Nautilus is not fastened to the shell by 

 any connecting tendon, like the rest of the testa- 

 ceous tribe, but has the power of leaving the shell 

 at pleasure, and as its appearance is widely differ- 



