528 Miscellaneous Implements Hxhibited at Wanoiclc. 
ing of the firms exhibiting, is not only an indication of the 
demand for such engines, but points to the direction in which 
such demand arises. 
The gas engine is no longer an engine useful merely for in- 
termittent work of small power. On the contrary, it is establish- 
ing itself in regular running factories as a rival of the steam 
engine — one firm having in hand at the moment six engines of 
100 horse-power; and where used in conjunction with its own 
Dowson gas-producing plant, it gives highly economical results. 
Although most of the gas engines exhibited were similar 
in principle, in their details there was just so much difference 
as would arise either with the view of further simplification of 
some parts, or of avoiding the use of some detail of another maker 
which happened to be inconveniently protected by a patent. 
The Otto Cycle, described in the report on Messrs. Crossley’s 
engine in Vol. XIV. (2nd Series) of the Society’s Journal, is that 
generally used. The Campbell and the Trent Gas Engine 
Companies, however, adopt a different system, described in the 
notice of their exhibits. 
The one important improvement in gas engines generally 
is the substitution of the ignition tube for firing the charge, 
instead of the original slide valve and flame. The slide valve, 
especially where gas was at all foul, was a source of trouble, and 
the flame firing direct was affected very much more by draughts 
than the system now adopted. 
Taking the exhibits in their catalogue order, the first were 
those of Messrs. Roheij & Co., of Lincoln (Stand 249), who 
exhibited two gas engines, one of 5 and the other of 12^ 
horse-power. They are designed under Messrs. Richardson and 
Norris’s patent, and work on the Otto Cycle. They are similar 
in arrangement to the oil engines exhibited by the same firm, 
which will be found described later, with the e.'iception that the 
firing of the gas is done by an ignition tube. 
Messrs. Wells Brothers, Sandiacre, 13erby (Stand 252). A small 
gas engine of ^ horse-power was exhibited as a “ new implement.” 
In its arrangement it is a distinct departure from all the 
other gas engines, — the novelty consisting in a rotary valve 
placed at the back of the cylinder through which the mixture of 
gas and air is admitted, and which also controls the exhaust. 
The valve is actuated by a ratchet wheel and pawl worked by a 
rod from the prolongation of the crank-pin of the engine. 
While the engine is running at its normal speed, one tooth 
of the ratchet is engaged by the pawl at each revolution of the 
engine. If the speed increases, the pawl acts as an inertia 
governor, and slips over the ratchet wheel without engaging in 
