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DRESSING OF ORES 



THE STRAKE, TYE, AND STRIP. 



These appliances may bo considered modifications of each other. Instead of effecting 

 a separation by relying upon subsidence according to the specific gravity of the sub- 

 stances, they are mechanically impelled against a volume of water so regulated as to 

 carry off the lighter particles. 



Fig. 715 represents the ground plan ofastrake employed in the lead-mines of Wales. 



715 



Its extreme length is about 18 feet, width 3 feet. The top increases from 18 inches 

 to 2 feet 9 inches wide. It is constructed of wood, the bottom being covered with 

 sheet-iron. 



The tye is usually 20 feet long, 2 feet wide, and is often employed for cleaning 

 hutchwork. In some instances when the ore or dradge is very rich, it is crushed, and 

 then tyed into heads, middles, and tails, the first portion going to pile, the middles 

 re-tyed, and the tails treated as refuse or washed in the buddle. 



Fig. 716, A, inflow of water ; B, head of tye ; c, partition board. The stuff is intro- 



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duced into the cistern D, flows, over the inclined front E, and is broomed at F. Between 

 E and G are the heads, from G to H middles, H to i tails. At K is an outlet launder, 

 regulated with a shute. An outline plan of the tye is shown, fig. 717. 



717 



The strip also consists of a wooden box, with its bottom inclined at a greater or less 

 angle, in order to suit the character of the stuff to be operated upon. The object of 

 this apparatus is somewhat analogous to that of the separating box, viz. to deprive tho 

 ore of the fine particles with which it may bo associated, and thereby to enrich it for 

 subsequent treatment. A rather strong stream of water is employed, against which 

 the mixed mineral is violently projected by means of a shovel. When ores are strong 

 and clean in their grain, but little loss can occur from this process, provided proper 

 care be exercised in conducting it ; but if their structure be delicate, and tho consti- 

 tuents intimately mixed, tho wastage must necessarily by great. 



Tho illustration, fig. 718, shows a strip, coffer, and settling cistern, with filtering 

 apparatus contrived for lead ore. A, vertical launder 6 inches square, delivering water 

 into tho box B, 9 inches long by 26 inches wide at tho point c ; D, bottom of strip 

 covered with sheet iron, 6 feet long and 16 inches wido at K. At this point a ledge 

 of wood is sometimes introduced for tho purpose of modifying the velocity of tho 

 water and forming a kind of shallow reservoir, so as to allow the workman to stir tho 

 stuff. At the end of the strip a coffer, F, is fixed, 11 inches deep, 30 inches square ; 

 H, settling box, 6 feet long and 30 inches deep ; K, outlet for wasto water. At o is in- 

 serted a filtering launder. 13 inches deep, extending across tho cistern. At j a similar 



