Recovery of Copper froiYi its Solution in Mine Drainage. 307 



wooden grating (Q^r') was supported at about six inches from the 

 bottom of the tank ; on the top of this grating and about midway 

 between the fixed partitions (f), a movable partition (ni), sliding in 

 a groove, was run down from the top, to which it extended. The 

 gratings were covered with metals to the depth of about one 

 foot. By this disposition of the grating and the partition, the 

 course of the water is as follows : — Coming in over one of the 

 fixed partitions it spreads out over the metals, passes through 

 them and the grating into the open space below, then flowing 

 under the movable partition, it rises through the grating and 

 metals on the opposite side and flows over the fixed partition 

 into the next division in it to take a similar course. In this way, 

 the water is brought into intimate contact with a large body of 

 metals with very little agitation, and the precipitate on becoming 

 detached, accumulates in the space below the grating. These 

 tanks were filled up with broken pieces of pig-iron, which were 

 shaken up and turned over about twice a week, when the pre- 

 cipitate subsides under the grating, from which it is taken once 

 a quarter. 



This form of launder was found specially serviceable in short 

 and wide spaces underground, where several lengths of them 

 could be placed side by side, and the waters passed backwards 

 and forward through them.* 



In narrow levels, other forms of launders were used ; thus, in 

 the old headings and exploration drifts, the waters were caught 

 at the entrance as high as possible and carried forward in 

 launders (I) supported at the side of the level, and having a fall of 

 about one in fifty. (See Plate XXIII., Fig. I.) When they reached 

 the far end, the waters were discharged into the return launders(E), 

 which were placed on the other side of the level but much nearer 

 thefloor. Asalmostthe whole of the lower j)artof the level was thus 

 occupied, anoverheadtramway (R) was placed above for the convey- 

 ance of the metals to the launders and for the removal of the pre- 

 cipitate. For this, a single wire rope was stretched along the level, 

 at aboutnine inches from the roof, one end being firmly fastened, the 

 otherhaving an arrangement for tightening up by means of ascrew. 

 This rope was support edalongthelevelbyironsupports(S), hollowed 



* Thus, in oue space twelve feet square, the waters passed thi ough more than fifteen 

 Ions of pig-iron- 



