ON THE UNIVERSAL DELUGE. 425 



testaceous animals growing equally well in salt water 9 

 and in water nearly fresh ; and, again, fresh water ani- 

 mals living in salt water *. By artificial means the inha- 

 bitants of the sea may be changed into inhabitants of 

 fresh water ; as fresh- water animals are, in their turn, 

 converted into marine animals, so that, to decide con- 

 cerning the proper element of each individual species is 

 often matter of difficulty. Therefore, other circum- 

 stances besides that of containing salt must be taken into 

 account. The occasional plenty, scarcity, or absolute 

 want of food ; the soil being sometimes sandy, slimy, or 

 rocky ; the depth, extent, agitation or tranquillity of the 

 water ; and, finally, the quality of the air contained in it, 

 may be as instrumental in determining the habitation of 

 these animals, as the materials which the water holds in 

 solution. An excellent observer has indeed very lately 

 shewn in a treatise, which supports the idea of fresh-water 

 formations, that we possess no unerring character for dis- 

 tinguishing sea shell-fish from those of fresh water ; but 

 admitted, notwithstanding the transition above stated, we 

 can draw a line of distinction between them, we must not 

 forget that this investigation is neither regarding sea shell- 

 fish now existing, nor of our present waters. We indeed 

 draw our conclusion, and not without reason, from similar 

 conformation, similar modes of existence. But one of two 

 things must be ; either that the shell-fish, whose remains 

 are found in beds of rocks, lived in the water out of 

 which these beds were precipitated, or the water in which 

 they lived, was dislodged by other water containing the 



* In the salt lakes of Westphalia, we find Lymnaea and fresh water 

 plants in abundance. 



