180 ON THE MINERAL AND METALLIFEROUS [Ch. IX. 



almost solely of rock, full of irregular veins and bunches of 

 quartz of various forms and dimensions. And in veins 

 abounding in the substance of the rock, the metallic minerals 

 are not confined to the quartzose part, but are also dissemi- 

 nated throughout the included pieces of rock in grains, 

 nodules, and even in small veins : and in this case the ore has 

 all the appearance of being contemporaneous with the rock in 

 which it is enclosed. 



Extreme examples of this kind of veins, if viewed for the 

 first time, and without a knowledge of the intermediate links 

 by which they are connected with regular quartz- veins, would 

 not, perhaps, be regarded by geologists as veins ; indeed, they 

 pass at last insensibly into a regular layer of rock, and if the 

 ores still continue in numerous minute veins, we have such a 

 metalliferous rock as has been denominated a stock-work by 

 the Germans, an example of which occurs in Cornwall, at the 

 open mine of Carclaze. 



Another example of veins, which is not unfrequent in Corn- 

 wall, is when a layer of rock, differing from that adjacent 

 either in the degree of hardness, colour, or of an entirely 

 different nature, as an elvan or porphyry, contains so much 

 ore in bunches or veins as to be worked as a lode. In these 

 cases, also, the geologist would not recognise such deposits as 

 veins ; and yet they differ in no respect either in the manner 

 or distribution of the ores, in their mode of connection with 

 the adjoining rocks, in their course, dip, or in the usual phe- 

 nomena of intersections, when they meet with veins of ordi- 

 nary descriptions. Indeed, what is still more to the purpose, 

 such deposits have been laid down as lodes in the sections 

 descriptive of the phenomena of veins, without their having 

 been distinguished in the miners' reports from lodes of the 

 ordinary character. 



It has been already stated, that the veins in the cliffs, and 

 and on the sea-shore, are not straight in their course, but run 

 in an undulating line, the curves of which are various and 

 irregular : and, along their whole length, they continually 



