83, which c c are 0 and sin 0~ along and perpendicular to the meridian ZC, we see that the com **ponent** angular velocities about the lines B

The motion of two such hyperboloids, turning in contact with each other, has hitherto been classed amongst cases of rolling ~ contact; but that classification is not strictly correct, for, although the corn **ponent** velocities of a pair of points of G contact in a direction at right angles --- to the line of contact are equal, still, - F as the axes are parallel neither to each - other nor to the line of contact, the velocities of a pair of points of contact FIG have components along the line of contact which are unequal, and their difference constitutes a lateral sliding.