e of city
gas upon this pipe it was found that the air pump must keep an air
pressure of 40 pounds, that the air and gas might mix properly at the
branch or fork, so we could get the best combustion and most heat from
our "blowpipe," for such it was. (Fig. 32.)

[Illustration: FIG. 31 and FIG. 32]

We were able to heat a tire so it could be moved in ten to twenty
minutes, and the machine may be said to have been satisfactory.

Gas, however, was not to be had at all places where it would be
necessary to change tires, and the item of cost was considerable.

To reach a result as good, if possible, experiments were begun with
coal oil (headlight oil). They were crude and unsatisfactory at first,
but soon success was reached.

A pipe was bent to fit the lower half of a wheel pretty closely and
then turned back under itself about the diameter of the pipe distant
from it. This under part had holes 1/10 in. diameter and 3 or 4 in.
apart drilled upon its upper side or under the upper pipe. Connected
with the upper pipe at its center was a pipe which ran to one side and
up to the can containing the kerosene. Between the can and the pipe
under the wheel was a stop cock, by which the flow of oil could be
controlled.

[Illustration: FIG. 33]

To use the device, open the cock and let a small amount of oil flow;
apply fire to the pipe under the wheel, and the oil in the upper pipe
is converted into gas, which flows out of the small holes in the lower
pipe, takes fire, and heats not only the tire, but the upper pipe,
thus converting more oil into gas. We had here a lot of blue flame
jets and the same result as with gas, but at less cost. We had also a
machine that was inexpensive and easily handled anywhere. Boxes were
placed over the upper parts of the wheels, that the heat might pass
closely to the tire. This device was extensively used by our people,
and with great satisfaction. In one way care had to be taken, viz.:
That in starting the fire it did not smoke and cover the tire with
carbon or "lampblack," which is a non-conductor of heat.

Experiments were made with air forced through gasoline, and with oil
heated in a can to form gas. There was more danger in either of these
than with our blowpipe device, and no better results were obtained,
though the cost was greater.

With the change of the wheels, the brakes had to be changed the same
amount, that is, each one set in 11/2 in. This it was thought would
either require