CELLS AND MANOMETER ATTACHMENTS. 7 



FIRST PROCESS. 



The dry and pulverized clays are sifted for the purpose of removing 

 the coarsest parts. Three empty alcohol barrels, each with a spigot 

 in the bung hole, are placed one above another, each of the upper two 

 being set a little back of the one below it. The uppermost barrel is 

 nearly filled with water, and into this is stirred about 3 kilograms of the 

 sifted clay. After standing quietly for 3 minutes, the spigot is opened 

 and the contents of the upper half of the barrel are allowed to flow into 

 the barrel below. The residue is removed and the barrel is recharged 

 and again partially emptied, precisely as in the first instance. When 

 the intermediate barrel is nearly full, its contents are likewise stirred 

 and then allowed to settle for 3 minutes, after which the spigot is opened 

 to allow the contents of the upper half to flow into the lowest recep- 

 tacle. The material which collects in the lowest barrel is bolted (wet) 

 successively through Nos. 10, 14, and 16 silk bolting-cloth, having 

 respectively 11,236, 19,600, and 24,336 holes to the square inch. The 

 proportion of the clay which is thus acquired is not very large. In one 

 instance where the original and final weights were recorded, 500 pounds 

 of the fire clay yielded 180 pounds of the bolted material. In another 

 case, 200 pounds of the Edgar clay gave 75 pounds of the final product. 



SECOND PROCESS. 



A wooden trough, 6 meters in length, with flat bottom and high sides, 

 is divided into several compartments by means of transverse dams. 

 The trough is given an inclined position, and in the highest compart- 

 ment the sifted clay is stirred up with water. The water with its sus- 

 pended matter is pushed from time to time over the dam into the next 

 compartment. By repeating the operation in the successive divisions, 

 the finer constituents of the clay can be quickly and quite completely 

 separated from the coarser. The material which collects in the last 

 compartment, or is allowed to overflow from that into other receptacles, 

 is bolted in the manner described above. 



The bolted clay is allowed to subside and the nearly clear water above 

 it is drawn off by means of a siphon, but there still remains a large quan- 

 tity of water in the clay which must be removed by evaporation, or 

 filtration, or by other means. Its removal by either of the methods 

 mentioned, however, is exceedingly slow and in many ways disagreeable. 

 A much better and more rapid method is that which was suggested to 

 us by our process for removing air from the porous walls of osmotic cells, 

 i. e., the method of "electrical endosmose." A largeporous pot (usually a 

 flower pot) is placed in a larger, water-tight vessel of any suitable mate- 

 rial. The clay (generally in the form of a thick porridge) is poured 

 into the former. Two electrodes are inserted, the anode into the con- 

 tents of the porous pot, and the cathode into the water which quickly 



