1st. _The speed of the piston is automatically slowed down at the end
of its stroke_, giving time for the column of water to come gradually
to rest, and for the valves to seat gently and quietly, avoiding all
concussion, jar, or the slightest tremor.
2d. _The speed of the engine can be adjusted and automatically
maintained as desired under any pressure._ Should it be working under
full head of steam and against a heavy pressure, and the pressure be
instantly removed the speed would continue unchanged.
3d. _The piston works to the end of its stroke under all pressures_,
avoiding the waste of steam incident to the piston falling short of its
stroke.
It will be understood that there is only a slight waste of oil caused
by the use of this apparatus—all the waste that there is, being the
small amount leaking through the stuffing boxes.
The term “Isochronal,” pump meaning equal spaces in equal times has
been applied to both these pumps and their valve gear.
The sizes, capacities, etc., of the pump described on the opposite page
are given in the following