_Outflow Tube and Piezometer._—The outflow tube and piezometer, H, J, K, L, is constructed as shown in Fig. 32. It should be made of barometer tubing having an internal diameter of about three millimeters. The tube is bent at J at an angle of forty to forty-five degrees. The knee J must be as acute as possible not to interfere with the inner diameter. The form and especially the magnitude of the outlet are of great importance. It must be circular and nearly 1.5 millimeter in diameter. It must not be larger than 1.67 millimeter nor smaller than 1.5 millimeter. The opening should be so made as to direct the stream of outflowing liquid in the direction shown by the arrow. [Illustration: FIGURE 32. SCHÖNE’S ELUTRIATOR, OUTFLOW TUBE. ] The piezometer L, K is parallel to the arm H, J, of the delivery tube. Its graduation has its zero point in the center of the outlet K. It commences with the one centimeter mark. From one to five centimeters it is divided into millimeters, from five to ten centimeters into one-fourth centimeter, from ten to fifty centimeters into one-half centimeter, and from fifty to 100 centimeters into centimeters. The dimensions given are those required for ordinary soils and for velocities ranging from two-tenths millimeter to four millimeters per second. For greater velocities, a delivery tube with a larger outlet must be used and the piezometer must be of greater internal diameter than indicated. [Illustration: FIGURE 33. SCHÖNE’S ELUTRIATOR, ARRANGEMENT OF APPARATUS. ] _Arrangement of the Apparatus._—The apparatus is conveniently mounted as shown in Fig. 33, giving front and side views of all parts of apparatus in position ready for use. When numerous analyses are to be made much time is saved by having a number of apparatus arranged _en batterie_. _The Sieve._—The soil, before being subjected to elutriation, should be passed through a sieve of which the meshes are 0.2 millimeter square. _The Process._—To measure the diameter of the cylinder, two marks are made with a diamond upon the glass which are distant from each other a certain space, for instance, _h_ centimeters. The space between these two marks is filled with water exactly measured. Suppose that a cubic centimeters were used, then the diameter is determined by the formula: D = √(4_a_)/(π_h_) centimeters. In order to determine that the elutriating cylinder is strictly comparable in all its parts this measurement should be made upon several parts thereof.