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Knight's Mechanical Encyclopedia (ed. Knight) 2 0 Browse Search
Thomas Wentworth Higginson, Letters and Journals of Thomas Wentworth Higginson 2 0 Browse Search
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Browsing named entities in Knight's Mechanical Encyclopedia (ed. Knight). You can also browse the collection for Porteous or search for Porteous in all documents.

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Knight's Mechanical Encyclopedia (ed. Knight), W. (search)
elongated brass cup, and passes out between the upper and lower cups. Whistles. A (Fig. 7206) is Johnston's selfact-ing alarm-whistle. The rod a is adjustable in the tubular stem b of the ball, to suit the desired low-water level in the boiler. When the water falls below the fixed point, the descent of the ball opens a valve connected with the rod a, allowing steam to escape and sound the whistle. B shows the device attached to a Cornish boiler. See also low-water alarm. Porteous's whistle, for a railway or marine signal, consists of a single mouthpiece and a number of whistles of different tones arranged in the barrel. By the introduction of one discordant note, an extremely shrill vibra- tion is produced, its peculiar dissonance rendering it distinctly audible over other sounds. (See also Calliope.) The whistle, patent No. 46,910, March 21, 1865, gives also a variable sound. Wood's railway-whistle (English patent, May 22, 1841) is attached to the blast-pipe