the heap A. If we crush the stuff in B until this heap contains approximately the same number of stones as A did—which means, crushing every stone in B into about twenty pieces—B will become the counterpart of A. Selecting in the same manner 5 per cent. of B, there is got a third heap, C. This alternate reduction and pulverising must be carried on until a sample of suitable size is obtained. This may be expressed very clearly thus:—

A  =  1000 tons of rocks and lumpy ore.
B  =    50      "   "    rough stones,  1/20th of A.
C  =    2.5    "    "    small stones,  1/20th of B.
D  =    0.125  "    "    coarse powder, 1/20th of C.