Height of column Velocity in the elutriating Corresponding diameter of in piezometer. cylinder of 4.489 silt particles. _d_ = _h_ centimeters diameter. _v_ v(⁷⁄₁₁)0.0314 millimeters. centimeters. Observed, Calculated, millimeters. millimeters. millimeters. 1.5 0.222 0.220 0.0120 1.6 0.257* 0.252 0.0131 1.7 0.284 0.281 0.0140 1.8 0.306* 0.307 0.0148 1.9 0.323 0.332 0.0155 2.0 0.346 0.355 0.0162 2.5 0.427 0.451 0.0185 3.0 0.531 0.530 0.0210 3.5 0.577 0.599 0.0227 4.0 0.650 0.660 0.0236 4.5 0.694 0.717 0.0254 5.0 0.751 0.769 0.0265 6.0 0.850 0.864 0.0286 7.0 0.942 0.950 0.0304 8.0 1.050 1.028 0.0320 9.0 1.120 1.101 0.0334 10.0 1.170 1.169 0.0347 15.0 1.490 1.460 0.0400 20.0 1.730 1.710 0.0441 25.0 1.940 1.920 0.0476 30.0 2.100 2.110 0.0506 35.0 2.310 2.290 0.0532 40.0 2.460 2.450 0.0556 45.0 2.610 2.610 0.0578 50.0 2.770 2.750 0.0598 60.0 3.030 3.020 0.0635 70.0 3.290 3.270 0.0667 80.0 3.490* 3.500 0.0697 90.0 3.710 3.710 0.0724 100.0 3.870* 3.920 0.0749 Suppose the problem is by means of the apparatus tested above, to separate into a number of groups a mixture of silt particles, whose hydraulic values are found between the following diameters: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 millimeters. The table will show at once under what pressure of water the piezometer must be placed in order to give the values; _viz._, 1.4, 2.8, 7.0, 15.0, 29.0, 53.0, and 83.0 centimeters respectively.