Published online by Cambridge University Press: 27 March 2009
(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.
page 306 note 1 Int. Mitt. Bodenkunde, 1915, 5, 257–311Google Scholar; Koll. Zeit. 1916, 18, 33–48Google Scholar; Trans. Faraday Soc. 1922, 17, 327–348Google Scholar; Nefedof, , J. Exp. Landw. 1902, 3, 421–449Google Scholar, outlines a method similar in principle to that of Odén, but apparently purely empirical.
page 306 note 1 Landw. Versuchs Stat. 1918, 91, 41.Google Scholar
page 307 note 1 Koll. Zeit. 1920, 26, 100–121Google Scholar; ibid. 1920, 26, 121–138. J. Landw. 1921, 69, 6–32.Google Scholar
page 307 note 2 As for instance in the method of reading the height of the water column.
page 307 note 3 i.e. percentages of material of a given particle size or Smaller.
page 307 note 4 Cf. Whittles, , J. Agric. Sci. 1922, 12, 166–181.CrossRefGoogle Scholar
page 309 note 1 For the effect of temperature on the viscosity coefficient of water, see Hosking, , Phil. Mag. 1907, 17, 509Google Scholar; ibid. 1909, 18, 260.
page 309 note 2 Int. Mitt. Bodenkunde, 1915, 5, 276.Google Scholar
page 310 note 1 Or ΣA + organic matter = C, in the case of ordinary soils.
page 319 note 1 Cf. Joseph, and Martin, , J. Agric. Sci. 1921, 11, 293–303.CrossRefGoogle Scholar
page 320 note 1 A considerable number of clays have, in fact, been followed by this method as far as log , which appears to be near the lower limit.