46 



* 



description of some of the characters ; but an at- 

 tempt at definition must be reserved for the va- 

 rieties, and, even in these, it sometimes becomes 

 a description rather than a definition. 



Under each subdivision are placed those rocks 

 which belong* to it, or which, collectively taken, 

 form the family ; the individuals all bearing the 

 same geological relation to the general order, or 

 to the structure of the earth. To facilitate the 

 investigation of these, they are arranged, when 

 numerous, according to certain obvious peculi- 

 arities of composition or structure ; by means of 

 which the family is subdivided into portions, each 

 designated by one particular character. In this 

 part of the arrangement also, the same want of lo- 

 gical precision occurs ; and, if the classification of 

 the organized departments of nature is to be made 

 the test of what is right, it must necessarily ap- 

 pear defective. In some cases, the characters of 

 these rocks are of such a nature, that they might 

 be considered as species ; in others, they present 

 slight, and, sometimes, very transient variations. 

 But distinctions of this nature are, in fact, inap- 



