1040 Proceedings of Royal Society of Edinburgh. [sess. 
the axes are parallel to edges of the cubic arrangement, and the 
other direction of zero transverse force is parallel to the face 
diagonal. In fig. 6 the vertical axis is parallel to a face diagonal, 
the horizontal axis is parallel to an edge, and the other direction 
of zero transverse force is parallel to a body diagonal of the cubic 
arrangement. 
Now, Wallerant’s expressions for the components of induc- 
tion (§5) lead to precisely the above results as expressions for 
the transverse component of induction, taken as" positive in the 
direction of increasing 6 , provided that we write B = - 2&R. 
This gives no crucial test, so far as the sign of the effect is 
concerned, between his expressions for the components of induc- 
tion and those deducible from the theory here developed ; for 
B is positive while k is negative. Therefore the transverse 
component of induction when the force is nearly coincident with 
a quaternary axis should, on his view, be directed from that axis 
— so that the induction is inclined at a greater angle to the 
quaternary axis than the external force is ; and the same' result 
follows from the present theory. For a component of the outside 
field is required to balance the component of internal force 
