THE "SAILING" OF THE NAUTILUS. 



277 



probably take place, but in a somewhat different manner. 

 As the Nautilus inhabits a depth of from twenty to forty 

 fathoms, it is evident that the air within its shell would 

 be displaced by the pressure of such a column of water.* 

 Accordingly, in every instance of the capture of a Nautilus 

 the chambers of its shell have been found filled with water. 

 It is not improbable that the fluid they contain may be less 

 compressed, and exert less pressure from within outwards 



FIG. 33. SHELL OF THE PEARLY NAUTILUS (Nautilus pOlllpilius} . 



than that of the external superincumbent column of water, 

 and that by this unbalanced pressure under the same 



* "At 100 fathoms the pressure exceeds 265 Ibs. to the square inch. 

 Empty bottles, securely corked, and sunk with weights beyond 100 

 fathoms, are always crushed. If filled with liquid the cork is driven 

 in, and the liquid replaced by salt water ; and in drawing the bottle up 

 again the cork is returned to the neck of the bottle, generally in a 

 reversed position." Sir F. Beaufort, quoted by Dr. S. P. Woodward 

 in his Manual of the Mollusca. 



