Trials of Self-Unding Reapers at Aighurth. 151 
of the expansion C is drawn. At the end of this stroke the exhaust opens, 
and the piston returns, as shown by D, expelling the products of combustion. 
The governor acts by preventing the admission of gas when the engine runs 
too fast, so that more than two, or, indeed, more than a dozen revolutions 
may be made without the admission of any gas whatever. The ' Otto and 
Langen ' gas-engine, of which Messrs. Crossley Brothers have made such 
lartre numbers, and of which they have introduced so many improvements, has 
been found eminently useful as a motor where small powers are required. 
The ' Otto and Langen,' however, is somewhat noisy, and in some cases this is 
an objection. The new ' Otto ' engine, therefore, working as it does as quietly 
as an ordinary steam-engine, opens up a still further field for the employment 
of gas motors, while apart from its silent action it possesses other advan- 
tages. Numerous testimonials speak favourably of its action in daily practice, 
and its makers claim for it the following special meritorious features : — First, 
that the principle of combustion in this gas-engine is entirely new. In it an 
explosion does not take place in the ordinary meaning of the term. A small 
part only of the charge is combustible, which on ignition serves to expand 
the remainder, thus avoiding shock and effecting vast economy. The engine 
is also alone in the peculiarity of igniting its charge at the beginning of the 
stroke, leaving the whole of the stroke for effective expansion of the gases, 
instead of merely a fraction, as in other obsolete constructions. Secondly, 
this engine unites the greatest simplicity of parts ever yet attained in a gas- 
engine, or even in many steam-engines, with an economy and durahility often 
surpassing either. It is as silent as a steam-engine, and works with the same 
smoothness and regularity, having, of course, the immense additional advan- 
tages of starting at full power at once on the gas being lit, and, by dispensing 
with the boiler, of avoiding the dangerous and pecuniary risks, annoyances, and 
expensive attendance which a boiler entails." 
Riches and Watts showed a Porcelain Roller Mill (Wegman's 
patent). It has differential speed and sell-acting pressure for 
softening Fine Middlings, or breaking down wheat in prepara- 
tion for the stones. It is manufactni-ed by A. B. Childs and 
Son, 70, Fenchurch Street, London. The price is fixed at 80?. 
The machine is only 34 inches wide, by 42 inches long, and 
comprises two sets of rollers supplied from either side of the 
hopper. The surfaces are very smooth ; and their efficiency is 
attributed to their peculiar porous nature. The principal use of 
the mill is to prepare middlings for the sieves. This is ordi- 
narily effected by the tearing action of the stones ; whereas the 
rollers operate with a squeezing action on the particles of bran 
which are thus prevented passing through the silk, and thus a 
more perfect separation is effected. The idea of using rollers is 
not new ; cast-iron or steel rollers have been employed, but the 
inventor states, not having an equal porous surface, the meal 
coming from these rollers was caked, and could not be sifted 
without a further disintegrating process, which tended to 
destroy the beneficial effect of the rolling by rubbing the 
flattened bran particles into the meal. The quality of the 
flour rolled by this mill, after being sifted, was certainly ex- 
tremely fine. 
