132 FRESH WATER FISHES. 



To the same causes are also to be attributed the 

 annihilation of species, now only found in a fossil 

 state. Even the hardest rocks present the most 

 perfect forms of extinct fishes — under the name of 

 ichthyolites. Nor can it be doubted that chang- 

 es are continually going on in the constitution of 

 inorganic matter, which, while it blots wholly from 

 existence distinct tribes, will also eventuate in the 

 production of entirely new species. 



To settle down in the iron-bound notion that 

 the laws of nature are thoroughly understood, and 

 that there cannot be anything new presented un- 

 der the sun, is to confess our perfect ignorance of 

 phenomena of the most astonishing character. Like 

 the inexhaustible capacity of the human mind for 

 knowledge, are the resources of nature, yet men 

 too often complain that all the avenues to the 

 study of Natural History have been travelled, all 

 countries surveyed, and all the animal creation 

 minutely pictured and anatomised, and that noth- 

 ing remains to excite them to study, or compen- 

 sate for the labor of investigation. 



Alas ! this is only an excuse for indolence — 

 and thus thousands live, only to occupy space, 

 without interesting others, or being enlightened 

 themselves, and die at last, as they lived, without 

 contributing one valuable idea to the storehouse of 

 useful knowledge. 



