the same horizontal plane. The throw of the crank is five feet. There are
two differential plunger pumps, having upper plungers 20 inches in
diameter, and lower plungers 33 inches in diameter, with a stroke of 5
feet. These pumps are vertical, and placed beneath the engine bed-plate,
to which they are attached by strong brackets. The pump under the low
pressure cylinder is worked directly from its cross-head by an extension
of the piston rod. The other pump is worked by a trunk connection from
the opposite end of the beam. The radius of the beam is but fifty inches,
but the connections to it are made very long by links.

The lower plungers work through sleeves in diaphragms located in the
center of the pumps. In these diaphragms, the openings for the delivery
valves are made. These valves are similar in construction to those
previously described for the horizontal plunger pump. Their diameter,
however, is but 5¼ inches, instead of 6 inches, and there are 72 suction
and 72 delivery valves for each pump. It will readily be seen that the
action of these pumps is similar to that of the bucket and plunger; each
pump having one suction and two deliveries for each revolution of the
engine. The Ontario is designed to run at a maximum speed of 33
revolutions a minute; and the service required of it is to run regularly
144 hours a week, without a stop, which is performed with the utmost
regularity.

The differential pump was invented and patented, many years since, by a
party named James Ramsden, in Pennsylvania, who designed it for an
ordinary house pump. It was subsequently reinvented by the writer, who
first ascertained that he was not the original inventor upon applying for
a patent. A pump of this description was run at the Hecla mine for
several years, at a speed of 500 feet a minute; and its performance was
in every way satisfactory.