. Manual for railroad engineers and engineering students : containing the rules and tables needed for the location, construction, and equipment of railroads as built in the United States . meter, and themethod of using it for the measurement of elevations, with examples fromactual practice, the reader is referred to Professor Guvots tables in theSmithsonian Miscellaneous Collections; to the Manual of the Mercurial andAneroid Barometers, by J. H. Belville, of the Greenwich Observatory; and toan excellent pamphlet upon the Barometer, Thermometer, &c, by Commo-dore Thornton A. Jenkins, Chief of t
. Manual for railroad engineers and engineering students : containing the rules and tables needed for the location, construction, and equipment of railroads as built in the United States . meter, and themethod of using it for the measurement of elevations, with examples fromactual practice, the reader is referred to Professor Guvots tables in theSmithsonian Miscellaneous Collections; to the Manual of the Mercurial andAneroid Barometers, by J. H. Belville, of the Greenwich Observatory; and toan excellent pamphlet upon the Barometer, Thermometer, &c, by Commo-dore Thornton A. Jenkins, Chief of the Bureau of Navigation, U. S. NavyDepartment. \6 MANUAL FOR RAILROAD ENGINEERS. sure increases, this corrugated top is forced inwards or down-wards. When, on the other hand, the atmospheric pressure de-creases, the elasticity of the metal, aided by a spring or by acounterweight, tends to move it in the opposite direction. Thismovement of the top of the box is conveyed by a series of multi-plying levers to an index moving over a circular scale graduatedto correspond with the standard barometer. The several partsof this instrument are shown in Fig. 6. A A is the metallic box, wn. Fig. 6. with corrugated top, exhausted of air, and fixed to the bottom ofa brass case enclosing the mechanism of the whole is a small column, connecting the top of the box with the prin-cipal lever E D, the latter moving upon the fulcrum C. Themovement of the small end of the lever is carried by the rod Fto the short end of the bent lever G II, to the upper end of whichis attached the watch chain I I. This chain passes round a smalldrum upon ihe arbor carrying the needle N N at its upper small hair spring upon the arbor regulates the motion of theneedle. S is a spiral spring, which, by its tension, raises theprincipal lever D K, when the pressure upon the top of the boxis in any way lessened. The circular scale, seen in sectionat M, is graduated by comparing its indications under diff
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherbosto, bookyear1883
