NO. 14.] 



MECHANICAL COMPOSITION OF SAMPLES. 



27 



finest constituents it is impossible to distinguish the clay and the sand from 

 one another. For this reason, the part to the extreme left of the lower curve is 

 rather inaccurate; it is not drawn quite so far out as the upper one, as it 

 may be taken for granted that the mineral grains do not attain the same de- 

 gree of fineness as does the clay; but how small they can actually be, it is 

 impossible to say. 



In the following table are given the values by the aid of which the curves 

 are constructed. For the three smallest sizes — less than 001 mm., 001— 0"05 

 mm., and 005 — 0'5 mm. — the percentages are given, and the average height 

 of the curve for these sizes calculated from the percentages, by dividing by 

 6'36, 2'32, and 3'32 respectively. With regard to the larger particles, which 

 each occupy 1 unit of the scale, the height of the curve is equal to the per- 

 centage found in the preceeding table. The percentage of clayey matter in 

 the four smallest sizes is also given : particles of more than 1 mm. never con- 

 tain clay. 



Constituent Particles. 



As the samples throughout are rather varied in their mechanical com- 

 position, it is hardly possible to give any general opinion regarding the relation 

 between the forces that have aided in their deposition; they will therefore be 

 taken separately in the following pages. 



