with a naval ship of second rate in the dock, and the tide at
a stage which would give the minimum pumping necessary to
free the dock. The level of the 20th altar was considered as
the proper point, and the water was admitted through two of
the gates of the caisson until this level was reached; they
were then closed. The contents of the dock at this point is
5,963,921 gallons.

"The trial was commenced and continued to completion without
any interruption in a very satisfactory manner.

"In the separate trials had of each pump, the average
discharge per minute was taken of the whole process, and
there was a singular uniformity throughout with equal piston
speed of the engine.

"It was to be expected, and in a measure realized, that
during the first moments of the operations, when the level of
the water in the dock was above the center of the runner of
the pumps, that the discharge would be proportioned to the
work done, where no effort was necessary to maintain a free
and full flow through the suction pipes; but as the level
passed lower and farther away from the center there was no
apparent diminution of the flow, and no noticeable addition
to the load imposed on the engine. The variation in piston
speed, noted during the trial, was probably due to the
variation of the boiler pressure, as it was difficult to
preserve an equal pressure, as it rose in spite of great
care, owing to the powerful draught and easy steaming
qualities of the boilers.