a1 Adviser in Agricultural Chemistry, University College of North Wales, Bangor.
(1) The expression of mechanical composition by means of continuous curves is discussed. It is suggested that a convenient representation will be obtained by showing summation percentage as a function of the logarithm of settling velocity.
(2) The effect of a gel coating on the settling velocity of a particle is examined and it is shown that a reduction in velocity takes place which is a simple function of the thickness of the gel coating.
(3) A method is outlined by which the mechanical composition of a soil or clay is derived from determinations of the concentration of a settling suspension for different values of depth/time.
(4) A shortened method for mechanical analysis is described which gives results in good agreement with results obtained by the present standard method.
(5) The effect of various modifications in conditions of working is discussed.
(6) The nature of the concentration gradients in a settling column of a suspension is examined. It is shown that below the first few centimetres the change in concentration with depth is very gradual.
(Received July 08 1922)