Abstract
As usually known, clay suspension becomes less turbid with the elapse of time for settling. The change of this turbidity was traced by the transmittance of monochromatic light (610 mμ of length), expecting the change might reveal somewhat the nature of clay particle. Clay suspension, of proper concentration, was introduced into the glass cell (1 cm × 1 cm × 3.8 cm) equipped to electric photometer and a downward movement of suspension, through the slit 5 mm in height, was traced by reading the transmittance every 30 min. for 3 hours. At the beginning the suspension was so suitably kept that its upper margin reached the upper surface of the slit, and it was allowed to begin to settle. Consequently, a clear supernatant liquid could occupy the slit the more widely in height the more the time for settling passed. Of seven soils from genetic horizons of both Brown forest soil and Reddish brown soil (acid mineral soil), the transmittance of above means was determined, results of which were shown in Plate 1 and 2 (refer to Table 1). From Plate 1 and 2,it is obvious that the curves of soils from B_1 of Kokubunji (T51) and also from B_2 of Mizunami (M 3) were particularly of wave-like feature. The causes of wave-like feature may be explained in several ways. But, one of the causes may be the following fact : in the above horizons, soil particles are of comparatively heterogeneous nature and are inclined to settle somewhat in various manners. Of the causes, more experiments will be made.
