DRESSING OF ORES 



157 



with flanges 1 inch deep and tires from 2 to 3 inches wide. The turn table is of cast 

 iron. It does not rotate, but the waggon is easily directed to either line of rail by 

 means of the circular ring : the elliptical loops in advance serving to guide and 

 place the wheels on the rails. 



Lifting Apparatus. It sometimes happens that the surface is nearly level, and 

 affords very little natural fall. In such case the enrichment of ores becomes more 

 expensive from the necessity of shifting some of the various products by manual 

 labour, and of introducing lifting appliances in order to procure the requisite eleva- 

 tions for carrying out the various elaborative processes. It is, moreover, scarcely 

 practicable from the conformation of the ground to form useful reservoirs of water 

 within a reasonable distance ; neither does it commonly occur in such cases that a 

 free supply can be obtained for washing. 



The pumping engine is therefore required to furnish the requisite quantity of water. 

 This is generally conveyed over the floors by wood launders, often interfering with 

 each other and obstructing the direct circulation of 

 carts, railways, &c. Now if a stand-pipe or pressure 

 column were erected at the engine, and a main judiciously 

 laid throughout the floors, it is obvious that it would not 

 only remedy this evil, but also afford water for the several 

 washing purposes, as well as motive power for common, 

 dash, or other wheels, together with turbines, flap 

 jacks, &c. 



When an inconsiderable proportion of water has only 

 to be raised to a higher level the common shoe or chain- 

 pump will be found to render effective service ; but when 

 a larger stream is requisite it would be better to employ 

 the rotatory pump. This pump, jig. 766, has been brought 

 to great perfection by Messrs. G-wynne. A is the suction- 

 pipe, and B the discharge, the dotted lines showing the 

 discharge B, horizontal when required. 



Pumps of the following dimensions are stated to raise and discharge per minute for 

 medium lifts, say from 10 to 30 feet high : 



766 



Diameter of 

 discharge-pipe. 

 1 inch. 



3 inches. 



4 ,, 



5 



6 



7 



Diameter of 



suction-pipe. 



2 inches. 



4 



5 



6 



7 

 8 



Gallons of 



water per minute. 



25 



70 



150 



300 



500 



1400 



Stuff consisting of slimes and sand may be readily elevated by means of a Jacob's 

 ladder or the Archimedean screw. For short elevations, combined water and raff 

 wheels may be advantageously employed. 



767 



Fig. 767, A, water-wheel ; B, raff or inverted wheel ; c, axis of both raff and water 

 wheels, carrying a tooth driving wheel ; D, sizing trommel ; E, launder for inlet of 



