and clays on the basis of their position relative to (i.e. above or below) Casagrande's
'A'Iine - see later. Since some pure clay minerals plot below the A-line (see Dumbleton
and West (1966), for example) and some silts plot above the A-line (Clayton 1983)
this approach is not considered reasonable. Silts are fine-grained non-cohesive soils -
as such they have relatively good effective strength, compressibility and drainage
properties, from an engineering point of view. The separate identification of silts and
clays can therefore most easily be made on the basis of dry strength. Silts have very
low to low dry strengths, whilst clays have medium to very high dry strengths (see, for
example, ASTM D2488).