Appertaining to this matter, I have used a machine with the same sizes of wheels as those found in the Kangaroo, but in which the power devices were very close together, and I have found it comparatively free from slip; and I am also informed by riders of the machine called the Facile, in which the pedals are closer together, that it is remarkably free from the same difficulty. But these facts cannot be taken as a proof of the theory under consideration, for the reason that _ab_ the application of the formula _R_ = _W_ ———— to the two machines _ac_ just spoken of, at best, still gives, as a result, a large amount of side pressure, which in actual practice does not exist. What difference it may make in the Facile or other treadle machines that the point of application of power is in the rear of the driving axle, I cannot say, or what difference a lever motion would show as compared with the simple crank is also not apparent; in fact, there is very little of established data from which to draw a conclusion, and a good reason which would now deter any cautious man from offering much experience or any theory in the matter will be readily surmised after reading the following extracts from the _Cyclist_ on the subject. “SIDE-SLIPPING ON SAFETIES. “One of the principal causes of the falling out of favor of the ‘Kangaroo’ type of Safety was the great proneness it had to side-slipping upon greasy roads, and it was confidently and freely asserted when the rear-driver was introduced that this defect was, in its construction, overcome. That this is not the case every one who has had any extensive experience with this class of machine will admit; indeed, the side-slipping of the Safety is its one great fault. As our readers know, the forks of a Safety of this type are considerably sloped,—some more so than others. It matters not whether the forks are straight or curved, so far as the point we are dealing with now is concerned. The sloping of the fork places the wheel, unless travelling in an absolutely straight line, more or less on its side. The result is manifest. There is a strong force behind pushing it forward. So long as the ground gives enough frictional resistance to the wheel, well and good; but so soon as the surface is lubricated, as it is, by the slippery mud, then the tendency is at once to push the machine over. This tendency is increased, as with the side-slipping upon other forms of machines, by a sloping road surface, the side of a rut, or the cant of the machine in turning a corner; and, moreover, the harder the rider pushes the more chance there is of the machine slipping. Having, then, pointed out the cause of side-slipping, it remains for those who devote their time and talents to invention to overcome it. So far as we can see, a vertical steering-fork should do that which is