Since the finest grain-sizes above those classed as “clay” do not tend to “lighten” soils, but even to render them more intractable (“putty soils”), while coarser ones gradually change the dense clay-texture into the “loamy,” it is clear that in between there must be a neutral point, some grain sizes which by themselves do not influence soil texture either way. Discussion of numerous physical analyses, and some direct experiments, have led the writer to conclude that this theoretically neutral grain-size lies at or near the diameter of .025 mm., or .5 mm. hydraulic value. In correlating the results of analysis with the tilling qualities of the soil as to “heaviness and lightness,” therefore, that grain-size may usually be left out of consideration. PHYSICAL ANALYSES OF SOILS AND SUBSOILS. (A) = 238 White Pipe Clay. Tishomingo Co. (Z) = Hygroscopic Moisture (+7 = to +21°C) ===========+==============+================+======= | Diameter | Velocity | |(Millimeters) | (Hydr. V.) | Designation| | | of +--------------+----------------+------- Materials. | | | | | Millimeters | (A) | | per sec. | -----------+--------------+----------------+------- Grit | 1-3 | | | | | { | .5-1 | | { | .50 | 64 |} Sand { | .30 | 32 |} 0.06 { | .16 | 16 |} { | .12 | 8 | 0.08 | | | { | .072 | 4 | 0.02 { | .047 | 2 | 0.04 Silt { | .036 | 1 | 0.08 { | .025 | 0.5 | 0.08 { | .016 | 0.25 | 2.00 { | .010 | <0.25 | 21.15 | | | Clay | ? | <0.0023 | 74.65 +------- | 98.16 | (Z) | 9.09 Ferric Oxid | 0.13 -------------------------------------------+-------