95 



OHAP. vi. 



VIEW OF THE EXTERNAL AND INTERNAL GENE- 

 RAL CHARACTERS BY WHICH ROCKS ARE DIS- 

 TINGUISHED. 



ROCKS, like the simple minerals of which they 

 are formed, are, independently of their composi- 

 tion, possessed of various characters more or less 

 obvious, by which they are capable of being dis- 

 criminated with a greater or less degree of cer- 

 tainty. Neither technical nor common language 

 however, are always sufficiently copious or precise 

 to serve the purpose of conveying ideas of some 

 of the minuter differences, which are still suffi- 

 ciently palpable to the eye. This defect is pro- 

 bably irremediable ; but it will nevertheless be of 

 use to enumerate the different circumstances to 

 which mineralogists have applied discriminating 

 terms ; as, in a great number of instances at least. 



