THE ARGONAUT. 123 



syphon Professor Owen continues : — " From these facts I 

 incline rather to the conclusion, that the sole function of 

 the air-chamhcrs is that of the balloon ; and that the power 

 which the animal enjoys of altering at will its specific gravity 

 must be analogous to that possessed by the freshwater tes- 

 taceous Gasteropods, and that it depends chiefly upon changes 

 in the extent of the surface which the soft parts expose to 

 the water according as they may be expanded to the utmost, 

 and spread abroad beyond the aperture of the shell, or be 

 contracted into a dense mass within its cavity. The Nauti- 

 lus may likewise possess the additional advantage of pro- 

 ducing a slight vacuum in the posterior parts of the chamber 

 of occupation, which is shut out by the horny cincture and 

 muscles of adliesion from the rest of that cavity."* 



It is scarcely a digression to introduce here some account 

 of the Paper-Nautilus or Argonauta argo, Linn. (Fig. 18), 

 with the history of which you must, to a certain extent, be 

 familiar, since it has been admitted into every work treat- 

 ing of the Wonders of creation, and some of our popular 

 poets have happily availed themselves of it. It is the 

 " little Nautilus" of Pope, who, with a certain class of 

 metaphysical inquirers, regards it as the source wdience 

 man has derived his first notions of ship-building ; it is 

 " the Ocean Mab, the fairy of the sea," of Byron ; but, of 

 cill our poets, Montgomery has the most beautifully de- 

 scribed it : — 



" Light as a flake of foam upon the wind, 

 Keel upward from the deep emerged a shell, 

 Shaped like the moon ere half her horn is fill'd ; 

 Fraught witli young life, it righted as it rose, 

 And moved at will along the yielding water. 

 The native pilot of this little bark 

 Put out a tier of oars on either side, 

 Spread to the wafting breeze a twofold sail, 

 And mounted up and glided down tlie billow 

 In happy freedom, pleased to feel the air. 

 And wander in the luxury of light." 



This description, although poetical, is in perfect accord- 

 ance with that which has been handed down to us from a 

 very early period. " But among the greatest wonders of 

 nature," says Pliny, " is that fish which of some is called 

 Nautilos, of others Pompilos. This fish, for to come aloft 



* Lcct. on the Invert. Anim. 330. M. Vrolik has proved that the 

 chambers of the shell contain only gas with a greater proportion of azote 

 than the atmospheric air, but no carbonic acid. — Ann. and Mag. N. Uist. 

 xii. 174. 



