Descripción
Broadside, 14 x 10 3/4 inches, including four engraved illustrations. Old folds. Four small tears at right margin (no loss of text), some wear and light staining. Contemporary inscriptions in ink and pencil on verso, ink has bled through to recto. Good. An apparently unrecorded marketing broadside for W.W. Dunn's newly enhanced patent for "Valve, Piston and Cylinder Heads," which promise to potentially double the pressure, and thus the power, of new and existing steam engines. The broadside has a prominent header framing engravings of the new valve, piston, and cylinder. Dunn explains10:46:16 AM "The pressure on the top of the Valve is counterbalanced by a corresponding pressure from the underside of the same in the Steam Chamber, completely freeing the action of the valve so that one-fourth of an inch wire will work the Valve of an Engine of 20 Horse Power; the pressure thus obtained can be increased or decreased (at the option of the Engineer) from 25 to 50, 75 or even 100 per cent. or more.It is hardly possible to calculate with precision or great exactitude the amount of power gained by this important discovery, but it certainly will not be less than 100 per cent., and will probably reach beyond 150 per cent." Although Dunn is the patent holder, the bottom of the sheet instructs that "for further particulars inquire of W.H. Patten, Custom House Block, Sansome St.; or at C.P. Kimball's Book Store, No. 122 Commercial Street, San Francisco." We could not find much biographical information about William Wallace Dunn, though it appears he was designing engines as early as 1858, as the REPORT OF THE FIRST INDUSTRIAL EXHIBITION OF THE MECHANICS' INSTITUTE OF THE CITY OF SAN FRANCISCO. notes Dunn's submission of "Two Models of Steam Engines, a Cylinder, a Valve, and a Hydrostatic Machine." There are also a variety of related patents secured by Dunn over the years, including an "Improvement to Type-Casting Machines" in 1871 and a "Rock Drilling Machine" in 1877. N° de ref. del artículo WRCAM57578
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