68 Proceedings of Philosophical Societies. [July, 



veins of Cornwall run east and west. They have frequently 

 been followed for two miles ; but in no instance traced to a 

 termination, either in length or depth, being always relinquished 

 when no longer worth working. The deepest mine in Cornwall, 

 Dolcoath, is 228 fathoms below the surface. They vary in 

 thickness, from one foot to three ; though there are instances of 

 veins 24 or even 30 feet wide. The veins are distinguished by 

 names, according to the nature of the veinstones. The following 

 are the principal: — 1. Gossany, when the veinstone is clay, 

 mixed with silica, and oxide of iron. Its colour varies from 

 light yellow to deep brown. This is the most common vein- 

 stone, and is considered as promising both for copper and tin. 



2. Sparry, when quartz predominates. It is rather unpromising. 



3. Mun dicky, when iron pyrites abounds. It is considered as 

 rather promising. 4. Peachy, when the veinstone is chlorite. 

 It is more promising for tin than for copper. 5. Flookany, 

 whea one or both of its sides is lined with bluish white clay. 

 6. Caply, when the veinstone is a hard substance of a greenish 

 or brownish substance, chiefly a mixture of chlorite and quartz. 

 Tin is found in it ; but seldom copper. 7- P r y an yi when the 

 ore is found in detached lumps. 8. When a vein abounds in 

 blende it is called a Hack jack lode ; when it contains granite it 

 is called a growan lode. 



On Friday, Dec. 18, Mr. Philips's paper on the veins of 

 Cornwall was continued. The contents of a vein are divided 

 i.ito those which are valuable, and those which are not so. The 

 latter are called deads, and are left as much as possible in the 

 vein. Sometimes large wedge-shaped fragments of rock occur 

 in veins called by the miners horses, partially cutting off the 

 contents of the vein, though seldom entirely obstructing it. 

 Veins of copper ore are liable to total obstructions without any 

 obvious cause. In proportion as the rock becomes harder, the 

 vein always becomes narrower. 



Copper mines were formerly considered as peculiar to slate ; 

 but of late they have been found to pass freely from slate to 

 granite, and back again, without deterioration. 



The metalliferous, or east and west veins, are crossed by 

 others, the direction of which is nearly north and south. These 

 are called cross courses, and rarely produce any metallic sub- 

 stance. There is another species of vein, called a con t re or 

 counter, the direction of which is for the most part north-east 

 and south-west. They are usually metalliferous, and often very 

 rich. 



On Jan. 1, 1813, Mr. Philips's paper on the veins of Corn- 

 wall was concluded. The remainder of this very valuable paper 

 consisted of accounts of particular Cornish veins, not very 

 susceptible of abridgment. 



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