VEIN. 



and carbonate of lead, and has formerly been worked for 

 the lead and copper, and more recently for the cobalt. 

 Mr. Williams, in his " Natural Hillorvof the Mineral King- 

 dom," defcribes a lingular itratum of ftone near Loffymouth, 

 in the (hire of Moray, of about eight feet thick, which is 

 compofed of feveral fpecies of hard and fine ilones of various 

 beautiful colours. " This ftratum is a kind of pudding-ftone, 

 in the compofition of which there is blended about an eighth 

 part of good blue lead-ore or galena. 



" This curious bed of (tone is nearly horizontal, but dips 

 away with an eafy (lope towards the north of the Moray 

 Frith. The lead is found in larger and fmaller grains and 

 flowers, blended through the whole body and compofition 

 of the ftone, in the fame manner as the fmall maffes of 

 agates and coloured cryftals, and other fpecies of ftone, are 

 found blended through the whole body of the ftratum." 



Where metallic ore is thus intermixed with fragments of 

 rock forming a conglomerate or breccia, it may probably be 

 referred to the fame kind of metallic repofitory as ftream- 

 ■works, (fee STREAM-fVoris,) in which particles and mafles 

 of ore are intermixed with loofe pebbles and fand, forming 

 beds at the bottom of valleys, or on the fea-(hore, the me- 

 tallic matter, as well as the pebbles, being derived from the 

 difintegration of rocks containing metallic veins ; but in the 

 inftance cited by Mr. Williams, the parts have become united, 

 forming a folid ftratum. 



The manner in which metallic veins were filled with ore 

 has greatly divided the opinions of geologifts. George 

 Agricola, a Saxon, who died in i ^jy, appears to have been 

 the firft writer who had any diftinft knowledge of the ftruc- 

 ture of metallic veins, which he pablifhed in a vrork entitled 

 " De Re Metallica," and another work entitled " Berman- 

 nus." His theory of veins is in fome refpecls ilmilar to that 

 of Werner, which has lately excited much attention. Accord- 

 ing to Agricola, the rents or fiffures which are filled with 

 metallic matter were partly formed at the fame time with 

 the rocks themfelves, and partly afterwards, by the waters 

 penetrating the fofter parts ; fo that where there has been a 

 larger quantity of water, or where the fubftance of the rock 

 has been much foftened, there the largeft fiffures occur. 

 With refpedl to the earths and ftones found in veins, he con- 

 ceives the former to ha^ve been detached from the rocks and 

 carried into the veins by water ; the latter he confiders as 

 ariung from the earthy matter, hardened partly by change 

 of temperature and partly by a lapidific juice. Minerals and 

 metals he regards as being depofited from a folution in water, 

 containing the earthy parts intimately mixed and combined 

 with it in certain proportions. The folution of thefe mi- 

 neral fubftances he conceives to have been greatly promoted 

 by heat, on the abftraftion of which they aifumed their pre- 

 fent folid form ; the precious metals being the refult of a 

 more pure and perfett folution. 



Becher, in his " Phyfica-Subterranea," publiiked in 1669, 

 afcribes the formation of metals and minerals to certain fub- 

 terranean vapours which arife from the bowels of the earth, 

 and penetrating the fubftance of veins, produce a peculiar 

 change in the earthy or ftony matter they meet with. He 

 regards the earth as a hollow body, filled with clay, water, 

 fulphureous and bituminous fubllances, from which arife 

 certain exhalations that form the metals. The celebrated 

 German phyfician Stahl, confiders veins, as well as the fub- 

 ftances they contain, to have been formed at the fame time 

 ■with the earth ilfelf, and of couri'e as being contemporaneous 

 with the rocks they iuterfeft ; but he is difpofed to attri- 

 bute fome elfeft to the a&ion of air and other caufes. 



Hcnkel, in his " Pyrilologia," lias given an ingenious theory 

 of the fonnation of metallic veins, whicli has been adopted, 

 7 



with certain modifications, by fome later geologifts : he attri- 

 butes the formation of ores to a peculiar exhalation pro- 

 duced and engendered by fermentation, fuppofed by him to 

 take place in the interior of rocks. The bafis of each ore 

 and mineral he fuppofes to exift in the fubftance of the 

 rock, and by a peculiar procefs of nature it is matured and 

 converted into the metal. He does not venture to afcertain 

 the nature of thefe bafes, but in one paffage he treats of 

 fubtle earths, in another of mercurial, arfenical, and ful- 

 phureous parts. Thefe three laft he probably confidered as 

 conftituent parts, and the metals as compounds. Air, 

 water, and fire, are fubftances, according to this mineralogift, 

 of which Nature avails herfelf in the formation of metals. 

 He alfo fuppofes certain kinds of earths and ftones to exift, 

 which ferve as the matrix for others, and which are indif- 

 penfably neceffary in the formation of minerals. 



Zimmerman, the pupil of Henkel, is the firft mineralogiit 

 who confiders veins to have been formed by a transformation 

 of the fubftance of the rock. Minerals, he fays, are un- 

 doubtedly formed in the rock ; but daily experience (hews 

 that the rock is not of itfelf capable of forming a metal, for 

 were the minerahzing principle capable of converting it into 

 a metal, we (hould find whole mountains which had under- 

 gone tbis change. But this change is only met with in 

 certain directions, where the part of a rock, being thus trans- 

 formed, conftitutes veins. Thefe veins, when they have not 

 fuffered an entire change, or when they do not contain perfett 

 metals, are ftill of a different nature from the reft of the 

 rock. An attentive examination will (hew that they are of 

 a decompofed and friable nature, appearing to have a ten- 

 dency to return to this natural earthy ftate, from which we 

 may conclude that thefe veins were originally the fame a^ 

 the rock, but that their texture had been altered and de- 

 compofed by fome particular faline fubftance, which pene- 

 trated the rents and fiffures, and had rendered them fit to 

 be transformed into minerals. 



Before noticing the theory of Von Oppel, which has fince 

 been adopted by Werner, we (hall ftate the opinions of thofe 

 geologifts who, with Henkel and Zimmerman, fuppofe that 

 veins have been filled by local caufes which may ftill continue 

 to operate ; whereas Von Oppel and Werner conceive that 

 they were formed by a general caufe, the operation of which 

 ceafed before the prefent ftate of the globe. Lehman, in his 

 treatife on the matrices of metals, publifhed in 1753, fays, 

 " the veins which we find in mines appear to be only the 

 branches and Ihoots of an immenfe trunk, which is placed at 

 a prodigious depth in the bowels of the earth, but in confe- 

 quence of its great depth we have not been able to reach the 

 trunk. The large veins are its principal branches, and the 

 inferior ones the twigs. What I have faid," he adds, " will 

 not appear incredible, when we confider that the bowels of 

 the earth are, according to every obfervation, the workhcuie 

 where Nature carries on the manufafture of the metals ; that, 

 from the beginning of the world, ibe has been working at, 

 and elaborating their primitive particles ; that thefe particles 

 iffue forth, in the form of vapours and exhalations, to the fur- 

 face of the globe through rents, in the fame manner as the 

 fap rifes and circulates thi-ough vegetables by means of the 

 veflels and fibres of which they are compofed." 



The latter part of the theory of Lehman, which fuppofes 

 that changes are now taking place in the interior of the globe, 

 by which metallic ores are ftill forming, has been fupported 

 by many geologifts, who have had opportunities of extenfive 

 obfervation. Mr. Von Trebra, fub-direftor of mines in 

 Saxony, in his work entitled " Obfervations on the In- 

 terior of Mountains," advances a theory nearly fimilar to 

 that of Zimmerman, and agreeing in part with Lehman. 



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