mitted diagonally in the direction through the side walls, fracture occurs in jagged lines in directions perpendicular to , the wave-path. The fissures at the end , therefore, commencing at top, very near the internal angles of the quoins, run down in the direction , making an angle with the plumb line of the wall (before disturbance) = the angle of emergence.
The portions of the side walls detached with the ends grow wider as they approach the base. They therefore make the end wall too rigid, to turn round upon or near its base, as in the former case (Fig. 21), to admit of the fissure opening; hence a cross fracture occurs somewhere below one-third the height of the wall , as at , which frees the mass and admits of its movement. This cross fracture may take any direction downwards from towards , dependent upon the nature of the masonry, &c., and the mass chiefly turns over, to the extent of opening of the fissure, round the joint at , or may partly slip upon
