440 GEORGE F. BECKER 
be at sensibly go° to one another and in scission as illustrated in 
Fig. 4 one of these directions will be horizontal, the other verti- 
cal. When the strain has become great the circular sections of 
the strain ellipsoid will no longer be at right angles. The angle 
between them is determinable in terms of the axes of the stress 
ellipse and (just as in pure shear) it is twice the angle whose 
Fic. 4.-—Flow distribution in scission. 
tangent is the least axis of the ellipsoid. Now since lines paral- 
lel to the axis of « undergo no change of length, one of the sets 
of circular sections must coincide with this direction throughout 
the strain so that the angle y vanishes. Hence also it one com- 
pares a scission with a pure shear in which the ultimate ellipsoids 
are equal or in which the amounts of distortion are the same, the 
range of the second set of planes of circular section is just twice 
as great in scission as it is in pure shear. In dealing with real 
solids (which always possess viscosity), and finite strains, this 
difference between pure shear and scission is of great importance ; 
but as scission alone is probably even rarer in nature than pure 
shear, it will be best to defer comment on this subject until the 
almost universal combination of pure shear and scission has been 
discussed. 
An inclined force? acting on a supported cube would produce 
among its effects a pure shear anda scission in one plane.’ It is 
*The precise direction of a force which would produce a given shear and a given 
scission is too complex a subject for this paper. 
2 When the mass is homogeneous and symmetrically placed with reference to the 
forces, the other strains produced would be a second pure shear at right angles to the 
first and a dilatation. The two pure shears would act independently of one another. 
