Upwards, are washed on plain sieve plates, but for finer-grained duff the sieve is covered with a bed of broken felspar lumps about 3 in.
As the sieve plate grows these non-cellulose regions swell and gradually become converted into the same kind of mucous substance as that contained in the tube; the two cells are thus placed in open communication.
Let us imagine unit mass of solution of volume V confined in a cylinder ABC between a fixed vapour sieve B and a solid piston A A B C FIG.
They are crushed to egg-size in a rock-breaker, and pulverized to pass a 40-mesh sieve in a California stamp-mill, which treats in 24 hours about 3 tons per stamp. A 10-stamp mill is fed by one rock-breaker, and discharges the liquid pulp into 10-15 wooden settling tanks, 9 by 5 by 8 ft., the settled contents of which are shovelled out and charged into the pans.
The companion cells are cut off from the same cells as those which unite to form the sieve tube.
Incomplete fusion occurs in sieve tubes.
Sieve Tubes.The sieve tubes consist of partially fused rows of cells, the transverse cr lateral walls being perforated by minute openings, through which the contents of the cells are connected with each other, and which after a certain time become closed by,the formation of callus on the sieve plates.
At an early period Wallsend was famous for its coal, but the name has now a general application to coal that does not go through a sieve with meshes five-eighths of an inch in size.
The space below the sieve thus formed is connected by means of an outlet tap with a closed tank, and this again communicates with a vacuum pump. By this means the filtration is quickened by the atmospheric pressure, and goes on very rapidly, as also does the subsequent washing.
The quick-lime is then slaked with the requisite quantity of water; the product is passed through a fine-meshed wire sieve and is spread in layers of 2 or 3 in.