PETRALOGY. 



A TREATISE ON ROCKS. 



INTRODUCTION. 



1. Illustrations of the present Arrangement. 



THE study of natural history has been divided by the most Division of 



natural 

 esteemed authors, and by the general voice, into three King- history, 



doms, the Animal, Vegetable, and Mineral. These have 

 again been subdivided into Classes, Orders, Genera, Species, 

 and Varieties. These terms may be considered as strictly pro- 

 per with regard to animals and vegetables ; but as their com- 

 mon meaning implies a vital or animated principle, their 

 application to the mineral kingdom, to which they have 

 passed rather by habitual use than after a due examination, 

 has become dubious ; and has given rise to many variations 

 and contradictions, and not a little obscurity. It is confessed 

 that human systems have but a very remote connexion with 

 the great operations of Nature, and are to be regarded as 

 mere artificial memories : hence in mineralogy some eminent Some terms 

 writers entirely reject Genera ; while others, with Dauben- 

 ton, say that there are no Species -, and Dolomieu has in vain 

 exhausted his acuteness and science to prove that real Species 

 exist in this department. With all his metaphysical prolixity 

 he has no disciples in this doctrine ; and the idea of a Species 

 remains dark, even to the most enlightened minds, because 

 it is false and unnatural, as in the other branches of natural 

 history a Species produces a similar progeny. 

 VOL. i. a 



