The futility of an effort to slip the machine sideways by a force upon the crank might be illustrated in this manner: Suppose the drive-wheel of an Ordinary is made rigidly fast to the front fork. Now, it would be impossible for the rider to slip the tire on the road-bed by pressure on the crank, as he can when the wheel is free to revolve in its bearings, no matter how long the crank may be; if the rider leans out over it, the machine could be rolled forward, but not slipped on the surface. Loosen the wheel so that it can revolve as usual, then it can be slipped, as every good rider well knows. Suppose now that the drive-wheel is rigidly fixed in the frame of the bicycle so far as any lateral motion is concerned, and the wheel cannot revolve within the system about any horizontal line at right angles to the axle of the wheel, as it would have to do in order to make it slip in the manner it would in the other case, then it is easy to see that the machine and rider might be rolled over sideways by throwing the weight on one crank; but it cannot be slipped: the only slipping that can occur is when the machine is allowed to get out of perpendicular, but the angle at which it would begin to slip would be the same regardless of width of tread. If the wide tread does affect the slipping, it is the result of other forces than those generally supposed. I do not believe that the extra weight on the drive-wheel will relieve the trouble. I have a Rover pattern machine in which the weight is almost entirely in the rear, and I can conscientiously aver that it is the worst slipper I was ever on. Now, this is in spite of the fact that there was every reason to believe, and to desire, that it should not slip at all. One of the _Cyclist_ correspondents mentions the American Star, and justly says that it does not slip; yet that fact could be explained by our formula, since it is a tall machine with narrow tread. I cannot see, after all, that any theory of wide or narrow tread could be applied to the Rover type, even if it were found to be valid in other cases, because there seems to be complaint, and I have found it so in practice, that the machine will slip more than the old Ordinary, even when not pushing on the cranks at all. It seems to slip worse than any other in making a curve or in descending hills and upon cobble-stones, whether there is any pressure on the crank or not. This will apply against the _Cyclist_ idea that the slanting fork breeds the mischief, since, if it slips in running a straight line, the slant of the fork could not possibly have anything to do with it.