Geology of Northumlerland. 267 



to view, the gangue was chiefly of spar, and contains nothing 

 metallic; but when the veins thus collected in a single Jissure 

 are followed to a great depth, ore is found in some of them." 

 This is a direct proof of the system which we have maintained, 

 M. Werner and myself, for the formation of veins; a system very 

 different from that which the author attributes to him, which 

 he certainly has not found in his works. 



Continuing the account of my travels, 1 say at p. 448, " It 

 was in t!ie side of this valley that M. Werner pointed out to me 

 the principal jjhaenomenon which had convinced him that veins 

 were fissures iilled up with substances precipitated against both 

 the sides of the space thus opened, and that phtenomenon was 

 precisely the same which had led me also to the same opinion. 

 In all veins, these new substances have on both sides been depo- 

 sited in symmetrical layers ; and the intervals between the sides 

 having i)een gradually narrowed by their accumulation, they 

 have at last united towards the middle ; where, however, there 

 remain some vacancic;, lined with small crystals. Now, in the 

 little veins ]\}^i described, M. Werner showed me a remarkable 

 circumstance, which at once proved the symmetrical accumula- 

 tion of the substances on the opposite sides of the fissur-es, and 

 the catastrophes undergone by the veins, after the formation of 

 the first gangne. These fissures have been evidently enlarged 

 by a new subsidence of the strata, which having been more con- 

 siderable on one side than on the other, has divided the first 

 gavg/ie in many places along the line of the first junction. The 

 same symmetrical iayers uniting incompletely towards tlie mid- 

 dle, have again been formed in the same manner as before. 

 This is a case which I have frequently observed in laige veins 

 where new fissures have taken place; sometimes towards the 

 middle, sometimes on one of the sides: and where the unequal 

 progress of the accumulation on the opposite sides is shown bv 

 effects on a greater scale, especially by large cavities, they are 

 always lined v\ith crystals, like that whicii I have described at 

 St. Andreuslerg in the Harlz, § 185." If the author, who 

 speaks of M. Werner's system without knowing it, had only 

 known my I'ravelsto Freyberg, published in London in 181u, he 

 would have found in it all the particulars above mentioned. 



M, Werner led me to the highest point of the mineral ground 

 of Freyberg, from which he pointed out to me the course of the 

 principal veins, crossing each other, as it happens when the 

 ground splits by dryness, or by unequal sinking. 



But the mineral region of Freyberg has a very different aspect 

 from what I had observed in other mineral countries. Had it 

 not been for the huldes or heaps of rubbish extracted from the 

 mines, and the outward machinery, it would have been impossible 



to 



