The four abutments with their retaining walls are of first-class rock-faced masonry.  The footing courses are stepped out liberally, so as to present an unusually large bottom surface.  They rest on beds of concrete 4 feet thick.  The foundation pits are about 50 feet below the top of the bluffs, and are in a material common to the Cleveland plateau, a mixture of blue sand and clay, with some water.  The estimated load of masonry on the earth at the bottom of the concrete is one and seven tenths tons to the square foot.  Two of the large abutments were completed last season.  They show an average settlement of three eighths of an inch since the lower footing courses were laid.

The facts and figures here given regarding the viaduct were kindly furnished by the city civil engineer, C.G.  Force, who has the work in charge.—­Jour.  Asso. of Eng.  Societies.

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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.

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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.