6 THIRD REPORT 1833. 



combated strenuously against the theory which considers veins 

 to have been rents that were afterwards filled up by different 

 mineral substances. 



This is the theory, however, which, from the time of Agricola 

 to the present day, has been most generally received, namely, 

 that veins were fissures which have been since filled tip by de- 

 grees with mineral matters. 



The causes of such fissures, and the mode of their contents 

 being deposited, have been variously stated, and have given rise 

 to much conjecture; and allowing for these differences, the main 

 proposition has been supported by many writers. Among these 

 I would name Agricola ; Balthazar Rosier, an eminent miner of 

 Freyberg, who died in 1673; Hoffman, a commissioner of mines 

 at the same place, in 1746; Von Oppel, before mentioned, who, 

 though he had indulged in other speculations, distinctly lays 

 down in his Introduction to Subterranean Geometry, (Dres- 

 den, 1749,) that veins were formerly fissures, open in their su- 

 perior part, and that they traverse and intersect the strata. 



Bergman entertained opinions very similar, which were also 

 supported by Delius, an author on mining, of considerable ce- 

 lebrity, who wrote about 1770. 



Gerhard, in his Essay on the History of the Mineral Kifig- 

 do7n, (Berlin, 1781,) gives a collection of interesting facts con- 

 cerning veins, and considers them to have originally been rents, 

 which wei'e afterwards filled up with mineral substances. 



To this list may be added Lasius, in his Observations on the 

 Mountains of the Hartx, in 1787; and Linnaeus is stated "to have 

 wondered at the nature of that force which split the rocks into 

 those cracks ; and adds, that probably the cause is very familiar, 

 — that they were formed moist, and cracked in drying*." 



In England we have testimony to the same opinion from 

 Dr. Pryce, who wrote his Mineralogia Cornubiensis in 1778. 

 He says, "When solid bodies were separated from fluid, certain 

 cracks, chinks and fissures in various directions were formed, 

 and as the matter of each stratum became more compact and 

 dense by the desertion of moisture, each stratum within itself 

 had its fissures likewise, which, for the most part, being in- 

 fluenced by peculiar distinct laws, were either perpendicular, 

 oblique," &c. 



He afterwards adds, that those very fissures are the wombs 

 or receptacles of all metals, and most minerals. He assigns the 

 derangements of veins to the effect of fracture by violence, and 

 quotes subsidence as one of the probable causes of such dislo- 

 cations. He says there can be no doubt that many alterations 



» Hill. 



