In carrying out the process thirty grams of sifted soil (two millimeters mesh sieve) are boiled with water for an hour and after cooling the soil and water are washed into the separating cylinder. The cylinder is then filled with water with constant shaking. After standing for ten minutes the stop-cock is opened and the water with its suspended matter allowed to flow into a porcelain dish. The cylinder is then again filled with water and the process is continued until the water drawn off is practically clear. The fine particles having been separated in this way the next coarser grade of particles is separated by repeating the process at intervals of five minutes. By these two operations it is considered that the clay is entirely removed. The residue remaining in the cylinder is dried and weighed. The relative proportions of clay and residue in the sample are thus determined. The residue is then separated into two portions by sieves of one millimeter and 0.5 millimeter mesh. The soil is thus separated into the following parts: 1. By the first sifting coarse quartz larger than two millimeters diameter. 2. Fine quartz two millimeters, to one millimeter diameter. 3. Coarse sand one millimeter, to 0.5 millimeter diameter. 4. Fine sand finer than 0.5 millimeter diameter. 5. Silt, clay, humus, etc., separated by the water. =200. Knop’s Silt Cylinder.=—The cylinder recommended by Knop[135] is essentially that of Kühn being furnished with four lateral tubes instead of one (Fig. 25). [Illustration: FIGURE 25. KNOP’S SILT CYLINDER. ] The sample of soil, twenty-five to thirty grams, after passing a two millimeters mesh sieve, and long boiling, is washed through a series of sieves of the following diameters of mesh respectively; _viz._, one millimeter, 0.5 millimeter, 0.25 millimeter, and 0.1 millimeter. The part which passes the finest sieve is placed in a Knop’s cylinder, the cylinder filled with water one decimeter above upper tube and well shaken. The cylinder is allowed to rest for five minutes when the upper cock is opened and the water drawn off. After five minutes more the next tube is opened and so on with equal intervals for the three upper tubes. The operation is repeated with fresh water until the water drawn off is clear. Finally the lowest tube is opened and all the water poured off of the sandy residue. The space between each tube is one decimeter. The dust remaining is dried and weighed and the weight of material carried over as silt determined by difference. =201. Siphon Silt Cylinder.=—Instead of the tubulated cylinder one furnished with a siphon can be employed[136] (Fig. 26). It should be about forty centimeters high and six centimeters internal diameter. The cylinder first receives twenty-five to thirty grams of the well boiled fine earth and then water until there is but a small space between it and the stopper when the latter is inserted.