ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 123 



Other large tin stockworks, differing little in essential cliar- 

 acter from those just described, exist at Glover, near Burngullow; 

 at Tolldish, on Tregoss Moor ; at Patwork,* near St. Columb (in 

 well-defined tourmaline schist) ; at Wheal Whisper, inWarleggan; 

 and many other places, but never far from the granite, and often 

 directly at the contact with it, or with elvan courses. There are 

 probably many others which might be worked, but that they do 

 not unite a sufficient number of the favourable conditions indi- 

 cated above. 



2. — TIN STOCKWORKS IN KILLAS CONNECTED OR ASSOCIATED WITH 

 LODES. 



Great Wheal Fortune. This mine is on the eastern border of 

 the parish of Breage, a little to the south of Grreat Wheal Vor. 

 Two well-known east and west tin and copper lodes traverse the 

 sett and dip to the southward at angles near 45*^. One of these 

 has been worked to a depth of 80 fathoms or more with consider- 

 able advantage, but has been idle for many years. Two series of 

 nearly vertical tin veins known as the " Conqueror " and "Eliza- 

 beth" branches appear at surface at about a furlong's distance to 

 the south of the outcrop of the main lodes, and have been worked 

 upon at intervals for many years in an excavation as a stockwork. 

 These branches probably are connected with the main lode at 

 a depth of 100 fathoms or a little more. The principal 

 excavation runs nearly S.W., is about 400 feet long, 50 feet wide, 

 and 60 feet deep. It is crossed by an elvan course which plainly 

 heaves the branches to the left, and seems to enrich them. 

 The average produce of the stuff stamped during the past few 

 years has been 12 lbs. of tin to the ton. As the scale of working 

 has been small, and steam power has been necessary for pumping 

 and for hauling the stuff from below the adit, this has scarcely 

 paid expenses, although on a sufficiently large scale it would 

 certainly have been profitable, since the tin is of high quality, 

 and the ground easy. 



The great open-work on the back of the " south lode " at 

 Drakewalls, was a kind of stockwork. The killas stockwork at 

 Polberrow in St. Agnes is well-known. Another stockwork in 



*Boase, Trans. Eog. Geol. Soc, Corn., TV., p. 250; Henwood, ibid v., p. 120. 

 According to Boase miicli of the rock at Fatwork has a brecciated appearance 

 " like a lime-ash floor," yet there is no well-defined lode known there. 



