be seen that when the horse is drawing the vehicle, the friction of
this large wheel against the ground being greater than that of the
concentric one within it, the latter will revolve until the center of
gravity of the whole is situated anew in a line vertical to the point
at which it bears on the ground. The result of such an arrangement is
that the driver rolls on the large wheel just as he would do on the
surface of an endless rail. As may be conceived, the tractive stress
is, as a consequence, considerably diminished.

There are two side wheels which are connected by a flexible axle to
the seat of the carriage, but these have no other purpose than that of
preventing the affair from turning to one side or the other.

The "swallow," for so it is named, is made entirely of steel and
wrought iron. It is very easily kept clean; the horse can be harnessed
to it in three minutes; and, aside from its uses for pleasure, it is
capable of being utilized in numerous ways.--_La Nature_.

[Our excellent contemporary, _La Nature_, is mistaken in its account
of the above vehicle. It is an American invention and was first
published, with engraving, in the SCIENTIFIC AMERICAN, December 16,
1882.]

* * * * *




BORING AN OIL WELL.