Metalliferous Veins. 165 



formation of veins." Hutton thought that elevatory forces 

 acting from beneath, originating in paroxysmal protrusions of 

 liquefied matter in the interior of the earth might have caused 

 them. It has also been supposed that the earth may have been 

 originally in a state of igneous fusion, and that as its tempera- 

 ture diminished, the external crust would crack during its cool- 

 ing. Mr Hopkins has investigated mathematically the results 

 which would obtain in a homogeneous mass acted on by an ele- 

 vatory force, and concludes that it would induce " two systems of 

 fissures with a certain general approximation, subject to certain 

 modifications to rectilinearity, and perpendicular to each other. 1 ' 1 

 Those at intermediate angles must therefore have originated at 

 different times. Were each system to have been completed at 

 one paroxysm we should have many such ; but where we 

 have, as in the metalliferous districts of this county, veins in 

 every direction, which both Mr Hopkins and Mr Fox think 

 may have opened " gradually or at intervals ;" many of them 

 many times " opened up" the elevatory forces, must have been 

 almost continually at work on one system or another. But Mr 

 Hopkins has shewn that parallel systems of fissures must ine- 

 vitably have been synchronous. Now, in many of our mining 

 districts the lodes form no inconsiderable portion of the whole 

 mass of the earth ; often, indeed, between two, the rock is not 

 very many times wider than one of them ; what would have 

 kept open these thin masses of rock, usually much inclined " and 

 of indefinite length and depth ?" The horses (in the north 

 they are called riders), replies the advocate of fissures. Why, 

 then, I reply, do we find no portion of the upper rock (killas). 

 fallen into the subjacent granite ? and why are the horses en- 

 tirely surrounded by the vein ; for until the substance of the 

 vein was deposited what supported it ? Werner, Mr Hopkins, 

 or Mr Fox replies, at first it was a mere crack or narrow fissure 

 kept open by the rubbish falling. I rejoin, if we must have a 

 crack and props to keep it open, is it more difficult to keep 

 abroad a wide than a narrow fissure ? If we must support the 

 same weight, may it not be as well kept a yard as an inch 

 apart? Mr Fox has said, " veins are often divided into 

 branches, which unite again at considerable depth, including be- 

 tween them vast portions of rock, perfectly insulated by the ore 



