Abstract

A new method of mechanical analysis of sands employing settling velocities has been developed especially for use aboard ship in geologic work connected with the ocean. Since coarse grains fall faster in water than fine ones, a mechanical analysis of a sample of sediment can be made by allowing the material to settle through a long column of water and observing the amounts of material which reach the bottom of the column during successive experimentally determined time intervals. A complete analysis requires about five minutes for most sands. Among the advantages over sieving, other than saving in time and labor, are: (1) The results obtained are more closely related to conditions of deposition, since actual deposition of sand in water depends upon settling velocities rather than on mere size of grains. This is illustrated by a comparison of sieve and tube analyses of the same samples of sand. (2) Data can be taken for a continuous frequency curve by which a more complete picture of the degree of sorting can be found.

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