554 Remarks on Dr. Boase's Primary Geology. 



" 9. It occasionally happens that where these granite-veins occur, 

 the slate is intersected by numerous small quartz-veins : some of 

 these are traversed by the former ; others, on the contrary, traverse 

 and heave both the granite-veins and the other quartz-veins." 



The 9th Chapter is devoted to a minute description of the 

 mineral and metalliferous veins in primary rocks, and the 

 author thus commences it : 



" Before concluding this sketch of the primary rocks, it is re- 

 quisite, in order to complete their description, to make a few obser- 

 vations on the mineral and metalliferous veins by which these rocks 

 are traversed. The details on this subject will be almost entirely 

 drawn from Cornwall, where the phenomena of veins have been 

 more extensively and more minutely investigated than in any other 

 country ; and, indeed, as far as works on this subject in our 

 language are concerned, Cornwall has been the principal source of 

 information. The metalliferous veins contained in the secondary 

 rocks are not unimportant, either in an economical or scientific 

 point of view ; but to enter on their examination, at present, would 

 be departing from the plan of this work, and would, if they were 

 fully treated of, require an entire volume. Besides, it is desirable 

 that the subject of veins should be carefully described under distinct 

 heads, according as the rocks with which they are associated vary 

 in their nature : and when a large body of facts has, by these means, 

 been collected, then our generalisations may be placed on a more 

 permanent basis ; but, at present, the facts which we possess con- 

 cerning veins are fully equalled, if not exceeded in number, by 

 speculations on their nature and origin. 



The vast importance of an accurate knowledge of veins to our 

 commercial welfare and prosperity, is generally admitted ; and 

 Geologists, also, have always regarded veins, not only as a curious 

 and interesting feature in the structure of the earth, but also as 

 affording valuable evidence concerning the internal movements and 

 convulsions which our planet has periodically experienced. Not- 

 withstanding, however, the high estimation in which this subject is 

 generally held, it is astonishing how little progress has been hither- 

 to made in this department of geology : every other branch of the 



