engine in commencing at half stroke.

The Lenoir igniting arrangement was complicated and troublesome. I have it
upon the table; the mixture was ignited at the proper time by the electric
spark produced from a primary battery and Ruhmkorff coil.

The Hugon engine was an advance in this respect, using a flame ignited,
and securing greater certainty of action in a comparatively simple manner.

It is really a modification of Barnett's lighting cock described in his
patent of 1838.

Other difficulties were found in using these engines; the pistons became
exceedingly hot. In the case of the Lenoir larger engines, it sometimes
became red hot, and caused complete ruin of the cylinder by scoring and
cutting up. Hugon to prevent this injected some water.

In the all important question of economy, these engines were found
grievously wanting, Lenoir consuming 95 cubic feet per I.H.P. per hour;
Hugon consuming 85 cubic feet per I.H.P. per hour.

The surviving engines of this type are only used for very small powers,
from one to four man power, or 1/8 to 1/2 horse, the most widely known of
this kind being the "Bischoff," which is very largely used; its
consumption of gas is even greater than the Lenoir, being 110 cubic feet
per horse power per hour, as tested with a half-horse engine at a late
exhibition of gas apparatus at Stockport.

So large a consumption of gas prevented these engines coming into extended
use for engines of moderate power, and led inventors to work to obtain
better results. The force generated by the explosion of a mixture of gas
and air is very short lived, and if it is to be fully utilized must be
used quickly; a high pressure is produced, but it very quickly disappears.

The quicker the piston moves after the maximum pressure is reached, the
less will be the loss of heat to the sides of the cylinder. The flame
which fills the cylinder and causes the increase of pressure rapidly loses
heat, and the pressure falls.

The idea of using a free piston was proposed as a remedy; it was thought
that a piston connected to a crank in the ordinary manner could not move
fast enough to utilize the pressure before it was lost. Many inventors
proposed to perform work upon a piston free from any direct connection
with the crank or shaft of the engine; the explosion after attaining its
maximum pressure expends its force in giving velocity to a piston; the
velocity so acquired carries it on against atmospheric pressure