iQl^ BuUi'izn of Lahoratoiics of DcnisoJi Ufitvcrsity. [Voi. xn 



that time all the washing done was by hand. The form of 

 washer used was a revolving-cylinder perforated with holes, and 

 fed inside by a constant stream of water. The ore was put into 

 the cylinder through a door, the door closed and the cylinder 

 revolved by hand until the ore was freed by running water 

 from the clay, when the ore was removed through the same 

 opening. The capacity of the washer was very limited, and 

 it could be used only on a small scale. Much of the smaller 

 ore was lost, but the larger fragments were thoroughl}' 

 cleansed. 



Later, a form of log-washer, similar to that used for cleans- 

 ing the brown iron-ores, was introduced, and is the form of washer 

 at present in use. Briefly, the log-washer consists of a long anci 

 stoutl)'-built box, of sufficient length and depth to contain the 

 log. The box, or trough, is elevated at one end. A log or 

 central shaft, 25 to 40 ft. long, carrying heavy iron-flanges, 

 spirally arranged the length of the log, revolves lengthwise in 

 the box or trough. The ore is fed at the upper end of tlie box, 

 and is gradually forced by the revolving log to the lower end, 

 where it passes out. A constant stream of water plays on the 

 ore in the box. The constant agitation and beating of the ore 

 by the log and the washing by water frees it from the adhering 

 clay. Steam is the motive power. 



