164- ON THE MINERAL AND METALLIFEROUS [Ch. IX 



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 concerning 

 veins are fully equalled, if not exceeded in number, by specu- 

 lations 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 in- 

 ternal movements and convulsions which our planet has 

 periodically experienced. Notwithstanding, however, the 

 high estimation in which this subject is generally held, it is 

 astonishing how little progress has been hitherto made in this 

 department of geology : every other branch of the science 

 abounds with copious and good descriptions, which are daily 

 increasing in number and in importance ; whilst that of veins 

 scarcely possesses any plain and honest details unencumbered 

 with hypothesis. Indeed, the low state of our knowledge of 

 these curious phenomena is plainly denoted by the neglect 

 with which they have been treated in the most recent and 

 most esteemed geological publications, Thus the student 

 looks in vain for any practical information on this subject 

 in the voluminous work of Lyell on the Principles of Geology : 

 and in the Manual of De la Beche, he must rest contented 

 with some short details ; indeed, the author has apologised for 

 the brevity with which he has treated this branch of the 

 science, and adds, that his notice of it " is solely intended to 

 call the attention of the student to a few interesting circum- 

 stances." We rather suspect that the confusion of facts and 

 theory in the descriptions of veins, rendered this subject unfit 

 for the pages of his practical work. In Macculloch's System 

 of Geology, also, although the account of veins occupies a few 

 more pages, yet it does not convey an accurate notion of 



