DESCRIPTION OF THE OPERATIONS AT DOLCOATH MINE. 195 



situations, and where the tin stuff to be operated on is of similar 

 quality, requiring little or no selection. 



The particles of tin being generally small, it is necessary to 

 reduce the stuff to a very fine powder before the worthless parts 

 can be separated from it. For this purpose two steam stamps are 

 employed, one of them of 120 heads and the other 60, besides 

 20 heads worked by water power in the winter months. In 

 ordinary working each of these heads of 6 cwt. is lifted 10 

 inches high 70 times per minute, and each head will stamp 

 about one ton of hard stuff in 24 hours, and proportionately more 

 according to the softness of the stuff. Much of the stuff is 

 stamped fine enough to pass through a grating containing 150 

 holes to a square inch ; but when the particles of tin are larger, 

 rougher grates are used. 



Our dressing operations * are all performed by the aid of the 

 "■ buddle " and the " kieve " ; trunks and frames of all kinds, which 

 were so extensively used a few years since, being entirely dispensed 

 with. The form of buddle we have adopted is that generally 

 known as the " centre cone buddle," its extreme diameter being 

 from 16 to 22 feet, and the diameter of the cone or centre from 

 5 to 8 feet, according to the nature of the stuff to be dressed. 

 On the top of the centre is a funnel with an iron plate attached 

 for distributing the stuff equally over the centre, and also three or 

 four arms for brooms or sweeps, which, together with the plate and 

 funnel, are made to revolve by machiq^ery driven by a water-wheel, 

 whilst around the buddle is a trench filled with water, into 

 which, whilst the buddle is being worked, the tails or worthless 

 parts of the stuff are thrown to be washed away after being 

 separated from the tin in huddling. The " stirring " and " packing " 

 in the kieves are also performed by water power. 



As arsenic is either mixed or combined with most of our tin 

 ores, it is necessary to calcine the ore in order to separate the tin. 

 This is effected by three of Brunton's Calciners, which need not be 

 particularly described, as they are in general use throughout the 

 county. The arsenic being driven off in fumes, is deposited in 

 flues above, and the tin stuff left behind is again dressed in 

 huddles and kieves, to free it from the remaining waste. When 



* Moissenet, Annales des Mines, Fifth Series, XIV, pp. 77 — 276. Mining 

 and Smelting Magazine, I, p. 16. Pearce, ihid, IV, p. 79. 



H 



