544 Remarks on Dr. Boase's Primary Geology. 



" If a rock be designated according to its geological relations, its 

 name must be liable to change, because the principles of the science 

 are not as yet permanently established ; besides, on this plan, in the 

 examination of countries previously unexplored, too much depends 

 on the correct judgment of the observer : but when a rock acquires 

 a name from the nature of its composition, whether purely minera- 

 logical, or blended with organic remains, then this part of the 

 science becomes perfectly descriptive, like the other branches of 

 Natural History; and much curious and accurate information may 

 then be expected from travellers who are not accomplished Geologists, 

 and Dr. Macculloch, although he has so strongly advocated the geo- 

 logical method of description, admits in his directions for conducting 

 geological observations, (' System of Geology,' Vol. II. page 473,) that 

 a correct description of its mineral character is necessary, as the 

 varieties of this rock are highly interesting, especially under its 

 passages into trap." 



If then it is generally admitted, that a particular mineralo- 

 gical character caused by one mineral, i. e. the superabun- 

 dance of hornblende, is interesting and worthy of notice, 

 why should not the same be allowed, and attended to, with 

 regard to other minerals ; Dr. Boase having shewn in Corn- 

 wall (and the same also occur in India) that the changes in 

 the primary rocks are highly interesting, and afford an oppor- 

 tunity for the most intricate researches. 



Dr. Boase thus unfolds the plan and object of his work : 



" In conducting the proposed enquiry, there are two objects which 

 demand attention : first, the description of the primary rocks both of 

 Cornwall and of other countries, in order to ascertain in what res- 

 pects they are analogous to each other ; and in the next place, an 

 examination whether the phenomena exhibited by these rocks are 

 in accordance with the principles of the prevailing theory. On this 

 plan the following pages will be nearly equally divided between a 

 narration of facts and hypothetical speculations ; and the former part 

 will lead to such lengthened preliminary details, as to constitute an 

 essay on primary geology : which so far from detracting from the in- 

 terest of the work, may perhaps impart to it a more permanent value 



