Of the relative merits of different forms of differential gear there is
little to be said. Perhaps it will not be thought I am unduly thrusting
myself forward, if I refer to a scheme of my own, in which no toothed
wheels are employed, but in which two conical surfaces are driven by a
series of balls lying in the groove between them, and jambed against
them by a recessed ring.

I have here a large wooden diagrammatic model, and a small working
model in steel, which shows that the new principle employed is correct,
namely, that a ball while jambed is free to turn, or if turning is able
to jamb. All Humbers, and most front steerers, employ differential
gearing; in some front steerers the clutch of necessity is used.

Neglecting for the present the different modes of transmitting power
from the pedals to the main wheels, it is possible now to consider the
four typical builds of tricycle. The only advantage that a rider can
find in a rear-steerer is the open front, so that in case of accident
he can more easily clear himself of his machine; as I have already
remarked, this power of instantly escaping seems to be considered by
many as of no importance.

In a rear-steerer which has not an open front, whether driven by a
clutch or by differential gear, I fail to discover any good quality.
The steering of a rear-steerer is so very uncertain, that such machines
cannot safely be driven at anything like a high speed, because any wheel
meeting with an obstruction will, by checking the machine, diminish the
weight on the steering wheel just at the time when a greater weight than
usual should be applied. It is for the corresponding reason that the
steering of a front-steerer is so excellent; the more the machine is