On the Cracks of Clay

Abstract

As seen in Pl. 10, a mass of clay plastered on a wooden board was cracked with the gradual dehydration.
On examining these, it is found:-
I. A linear relation between thickness of the clay plaster and size of the block produced as the result of cracking. The author took the distance between two neighbouring eracks along the contour line of the plaster (the line of equal thickness) to represent the size of the block.
II. Various forms of the cracks as to be classified as follows:
1. T-type. (Right-angled.) The most ordinary type.
2. H-type. Fig. 4.
3. L-type. Fig. 5.
4. ξ-type. Fig. 6 shows how the erack of this type grows.
5. Echelon cracks. Only seen on the surface of clay in its early stage of dehydration. (Fig. 7, left.)
6. Three-ray type.
(a) Fig. 8, a
(b) Fig. 8, b.
Three-ray cracks making angle of 120 degrees with each other were absent in the present experiments.