PlCTURESaUE CHARACTERS OF ROCKS. 53 



that the observer, thus qualified, should have been 

 long practised in the investigation of rocks in the 

 large masses in which they occur in nature, in different 

 countries, and under every variety of form and dis- 

 tribution ; and that he should, further, have studied 

 for himself the picturesque forms with which they are 

 usually associated. Neither descriptions nor drawings 

 can convey this instruction; and the advantages to be 

 derived from these circumstances are therefore such 

 as to be nearly limited to those who will pro- 

 bably have little occasion for them. To the geological 

 student, this knowledge cannot be communicated ; and 

 it is of the very essence of his imperfect attainments 

 in the science, to be unable to turn this delicate and 

 precarious species of information to use. 



I need not anticipate the difficulties and the uncer- 

 tainties in this class of observations, which render a 

 reliance on it objectionable in a general view; but 

 am at the same time willing to concede, that in the 

 hands of an expert and practised geologist, it may 

 often be rendered a useful accessary; furnishing va- 

 luable hints respecting circumstances which it is unable 

 to determine, but which may often direct the steps 

 and shorten the labour of the observer. But to 

 render this proceeding really useful, and at the same 

 time safe, these observations must not be extended 

 beyond particular countries, aad must often be limited 

 to very narrow districts. Although any particular 

 rockmaybe found to present various picturesque aspects 

 in different countries or distant tracts, it is occasionally 

 sufficiently consistent, in one place, to enable the geo- 

 logist to extend, by his eye or his telescope, those ob- 

 servations which he has elsewhere made by his ham- 

 mer mid his hand. Yet he will, in the following 



