360 ON THE APPARENT DISLOCATIONS [Ch. XV 



which have been worked ; and these are few compared with 

 those that have not been examined, and still more so with 

 those veins that are not metalliferous. Now these parallel 

 veins are supposed to be of the same age, and, being indefi- 

 nite, they, of course, reach as far as Mount's Bay, a distance 

 of seven miles ; conceive, therefore, the comparatively narrow 

 peninsula of the Land's End district, intersected by thousands 

 of open fissures, inclined at a great angle, and yet the severed 

 parts not falling together according to the known laws of 

 gravity. But, perhaps, it may be argued that, although these 

 veins belong to the same epoch, they were not absolutely co- 

 existent as fissures, having been successively formed at various 

 intervals during this period. Then we must fancy that con- 

 vulsions followed each other for a certain space in one direc- 

 tion, and afterwards operated in other lines, in order to 

 explain the position of the different series of parallel veins, 

 described by Mr. Carne : but we will shortly endeavour to 

 show, that the intricate interference of veins with each other 

 cannot be easily reconciled with this notion. 



We must not, however, leave this topic of fissures without 

 noticing the nature of the union which subsists between veins 

 and the containing rock, both as regards their respective 

 structures and composition. It has been stated, in the ninth 

 chapter, that large or true veins are often so situated as to 

 occupy, as it were, spaces parallel with the joints or seams of 

 the traversed rock ; that is, they are parallel with one or 

 other of the extended surfaces, resulting from the aggregation 

 of similar concretions. We will not, however, from these 

 facts venture on any generalisation, but repeat what we have 

 already stated before the British Association, that the subject 

 is worthy of careful consideration, in order to ascertain to 

 what extent, and under what particular circumstances, this 

 arrangement obtains. 



The same condition is of very common occurrence on the 

 small scale ; for though the line of contact between veins and 

 the rock, as between different kinds of rock, granite and 



