14 
BULLETIN C2, HAWAII EXPERIMENT STATION 
Since there is no agreement on the part of various investigators 
as to the limit in size of the various separates, it is thought best to 
express the figures obtained in a mechanical analysis as summation 
percentages as Robinson (30, p. 307) suggests, and to plot the differ- 
ent points obtained, connecting them by a curve. In this manner 
100 
0.002 
Figure 7. — Mechanical analysis. 
0.02 
0.005 0.01 
D/AMETERfMM.) 
Summation curves of the fine fraction of six 
Hawaii soils 
any intermediate point may be obtained by interpolation. The term 
" equivalent diameter " is used instead of " diameter " for obvious 
reasons, and the logarithm of the equivalent diameter is plotted in- 
stead of the equivalent diameter itself to avoid crowding the points. 
Figure 7 shows graphically these summation curves for six soils. In 
this manner smooth curves are obtained, making interpolation easy, 
