of Devonshire and Cornwall, 16i 



C. Of Alluvial Depositions of Ores, 



I agree with many mineralogists* in the opinion that these accu- 

 mulations of ore have been originally true veins, worn down and 

 removed by some cause or other from the place where they were 

 formed ; that they have been water-worn, and carried to a greater or 

 less distance, where they have been covered by alluvial soil. These 

 washed ores occur every where in similar situations, either in a plain, 

 or in open and very low-lying vallies, in beds or strata, which are 

 generally at a small depth below the surface of the ground, and often 



Westerwalde. This formation consists of copper pyrites, red oxide, of copper, malachite, 

 brown compact testaceous iron ore, with quartz. Nouvelle Theoric de la formation dc» 

 filons, p. 168. 



Werner endeavours to prove by this, that an analogy exists between the age of veins 

 and beds. But admitting the example just quoted (Werner does not give it as undoubted), 

 docs it follow that this formation of beds and veins in different countries is coeval ? has 

 not Werner himself told us, that veins of the same nature may be of different ages ? 

 * Klaproth's Mineralogical Observations on Cornwall, p. 11. 



Mr. Jars believes these fragments to be remains of heaps of refuse from the ancient 

 unskilful working of the mines, which by inundations have been washed down from the 

 mountains, and formed beds in the rallies. Ibidem, p 11. 



Pryce, who was a practical miner, divided the alluvial ores of tin into different 

 kinds. " The shade is disjunct, and scattered to some declined distance from its parent 

 " lode, and it is pebbly or smoothy angular of various sizes, from half an ounce to some 

 " pounds weight." Stream tin ore is the same as shade, but smaller sized, or arenaceous. 

 " It is the smaller loose particles of the mineral, detached from the bryle or back of sundry 

 " lodes, which are situated on hilly ground, and carried down from thence by the retiring 

 " waters, being collected in large bodies or heaps in the vallies. In the solid rock of the 

 " valley there is no tin ore, but immediately upon it is deposited a layer of stream tin of 

 " various thickness ; perhaps over that a layer of earth, clay, gravel, &c. upoTi that again 

 " another stratum of tin ore, and so on successively, stratum super stratum according to 

 " their gravity, and ihQ different periods of their coming thither." Pryce Mineralogia 

 " Cornubiensis. 



X 



