s
character, the advantage being, in addition to its necessity for the
work of turning the eccentric ahead or back, that the liability of the
engine to run away, as very often happens from the breaking of the
governor belt or a similar cause, was not possible.

The cut off valve has a travel considerably beyond the edge of the
steam passage after the valve is closed, and this has one advantage,
that the valve is less liable to leak, and to this must be added the
loss from the friction of this moving valve, and moving too in
opposition to the main valve. In our perfect valve, as we outlined it,
the valve does not move after the port is closed. The exhausting
functions of the valve are very good, giving a quick opening and a
full opening, because this opening occurs when the eccentric is moving
its fastest. The engine also possesses a distinct advantage in having
remarkably small clearance spaces. The length of the steam passage is
very small in comparison with any form of engine, and having but two
ports instead of four, as in the Corliss and four valve type.

In these there must be included in the clearance, that to the exhaust
port as well as the steam port, adding a considerable amount where the
piston comes close to the head. As the engines leave the maker's hand
the engines are provided with a considerable amount of lap to give
plenty of compression, but are, of course, capable of having more
added to increase compression, or some planed off to decrease it.

One of the peculiar things about this engine is the failure to realize
anywhere near boiler pressure, noticeable in every case that has come
under my notice. The considerable lead gives it for an instant, but it
soon falls away, indicating the steam chest pressure only by a peak at
the junction of the admission and steam lines. This is probably due to
the fact that the cut off valve commences closing the steam passage so
soon after steam is admitted, and in this particular does not satisfy
the requirements of a perfect valve. There is this about the engine,
that above all others of this type there has come under my notice
fewer engines of this type with a maladjustment of valves from
tampering by incompetent engineers.

* * * * *

FIRING POINTS OF VARIOUS EXPLOSIVES.

An apparatus, devised by Horsley, was used, which consisted of an iron
stand with a ring support holding a hemispherical iron vessel, in
which paraffin