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.

DIRECT ACTING STEAM PUMPS.

This class of machinery deserves a prominent place, as the number in use vastly exceeds those of all other types combined.

The first consideration will be given to the Worthington, which is the pioneer of its type, having been invented by the late Henry R. Worthington, and patented in 1844.  Mr. Worthington’s first pump was designed for feeding boilers.  His first water works engine was built for the city of Savannah, Ga., and erected in 1854.  The second engine, which was the duplicate of the Savannah engine, was erected at the city of Cambridge, Mass., in the year 1856, and was guaranteed to deliver 300,000 gallons in twenty-four hours to an altitude of 100 feet.  It had a high pressure cylinder 12 inches in diameter, placed within a low pressure cylinder 25 inches in diameter; the low pressure piston being annular.  The double acting water plunger was 14 inches in diameter, and worked directly from the high pressure piston rod; the stroke of pistons and plunger being 25 inches.  This engine was tested in 1860, with the result of a duty equal to 70,463,750 foot pounds per 100 pounds of coal.  Subsequently, a test made by Mr. Frederick Graff, of Philadelphia (long prominently connected with the Philadelphia Water Department), and the late Erastus W. Smith, of New York, developed a duty of 71,278,486 foot pounds per 100 pounds of coal, which long remained the best record in the United States.  In 1863, Mr. Worthington brought out at Charleston, Mass., his crowning success, the duplex engine, which fairly deserves to be placed first among the hydraulic inventions of this century.  This engine has since been more extensively duplicated for water works purposes than any other, with the possible exception of the Cornish.

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IMPROVED GUN PRESSURE GAUGE.

The following description of the construction and mode of action is by Thomas Shaw, M.E., Philadelphia, the inventor.

[Illustration:  IMPROVED GUN PRESSURE GAUGE.]