154 



DRESSING OF ORES 



a copper bottom sieve, or else submitted to the action of a tye, or other suitable 

 apparatus. 



757 



758 



IB 



ftwrniWi'TVZvww'&Win/ii 



, 



Machine Dotty Tub. This tub, Jiff. 759, is packed by machinery represented in the 

 accompanying woodcut, in which A is a small water-wheel, working a vertical shaft 

 B, and driving another shaft o. At the bottom of this is fixed a notched wheel D, which 

 presses outwardly the hammers E E ; these are mounted upon iron bars F F', and 

 violently driven upon the side of the kieve by means of springs G o'. 



The degree to which ore can be concentrated by dollying must evidently depend 

 upon several conditions : 1st. The initial percentage of the ore. 2nd. The con- 

 dition to which it is reduced. 3rd. The matrix with which it is associated. 4th. 

 The proportion of water employed. And lastly, if the rotation and packing have been 

 judiciously performed. An experiment upon some sand slime load ore, much inter- 

 mixed with fine carbonate of iron, gave the following results : 

 Introduced into dolly tub, 17 cwts., assayed, 48 per cent 



Time required to introduce stuff .... 6 minutes. 



Dolly rotated 6 



Dolly withdrawn 



Tub packed 5 



Running off water . 6 



Skimming and cleaning out tub 20 



Total 



. 42 



