800 ' NEW YORK STATE MUSEUM 



tains an axis with, iron arms, tlieir revolution serving to break np 

 tlie clay, whicli is charged through, a hopper at the top. A cur- 

 rent of water passes through the cylinder and carries the fine clay 

 particles with it, while the coarse ones are left behind in the 

 machine. The speed of the current has to be regulated by experi- 

 ment, for if too much water is used coarse material will be washed 

 out of the cylinder, and conversely if the current is too slow the 

 clay will not yield a sufficient percentage of washed product. One 

 objection to this apparatus is that it lias to be stopped from time 

 to time to remove the coarse sand from the machine. 



The method most commonly used at the present day for washing 

 kaolin is in its general detail as follows : 



As the kaolin comes from the mine it is generally discharged 

 into a log washer, a semicylindric trough, in which revolves a 

 horizontal axis, bearing short arms. The action of the arms breaks 

 up the kaolin more or less thoroughly, according tO' its density, 

 and facilitates the subsequent washing. The stream of water 

 directed into the log washer, sweeps the kaolin and most of the 

 sand into the washing trough, which is about 15 inches wide and 

 12 inches deep, but should be wider and deeper if the kaolin is 

 very sandy. The troughing is about YOO feet long, and to utilize 

 the space thoroughly it is broken up into sections (50 feet each 

 is a good length) these being arranged parallel, and connecting at 

 the ends, so that the water, with suspended clay, follows a zigzag 

 course. 



The troughing has a slight pitch, commonly about one inch 

 in 20 feet, but the amount depends on the kaolin, and whether the 

 contained sand is fine or coarse. If the kaolin is very fine, and 

 settles slowly, the pitch need not be so great, and vice versa. A 

 large quantity of very coarse sand in the kaolin is a nuisance, as 

 it clogs up the log washer and the upper end of the trough more 

 quickly, causing much labor to keep them clean. As it is, con- 

 siderable sand settles there, and, to keep the trough clear, sand 

 wheels are used. The wheels are wooden, bearing a number o£ 



