ng. Societies._

* * * * *

For sticking paper to zinc, use starch paste with which a little
Venice turpentine has been incorporated, or else use a dilute solution
of white gelatine or isinglass.

* * * * *

CENTRIFUGAL PUMPS AT MARE ISLAND NAVY YARD, CALIFORNIA.[1]

[Footnote 1: Built by the Southwark Foundry and Machine Company,
of Philadelphia.]

By H.R. CORNELIUS.

In December, 1883, bids were asked for by the United States government
on pumping machinery, to remove the water from a dry dock for vessels
of large size.

The dimensions of the dock, which is situated on San Pablo Bay,
directly opposite the city of Vallejo, are as follows:

Five hundred and twenty-nine feet wide at its widest part, 36 feet
deep, with a capacity at mean tide of 9,000,000 gallons.

After receiving the contract, several different sizes of pumps were
considered, but the following dimensions were finally chosen: Two 42
inch centrifugal pumps, with runner 66 inches in diameter and
discharge pipes 42 inches, each driven direct by a vertical engine
with 28 inch diameter cylinder and 24 inch stroke.

These were completed and shipped in June, 1885, on nine cars,
constituting a special train, which arrived safely at its destination
in the short space of two weeks, and the pumps were there erected on
foundations prepared by the government.

From the "Report of the Chief of Bureau of Yards and Docks" I quote
the following account of the official tests:

"The board appointed to make the test resolved to fill the
dock to about the level that would attain in actual service
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 expect