. The railroad and engineering journal . the column of mercury will stand just 30 in. high in thetube. As we rise above the sea-level the pressure of theair grows less, and the column of mercury falls. In roundnumbers the mercury falls i in. for each 1,000 ft. we rise;so that, knowing this, we can tell approximately how high pends upon the diameterof the circle. In a 5-in. barome-ter the needle is 3 in, long, and the diameter of the circleis the same. In this case, the length which correspondsto I in. of the mercurial barometer is about \]i in. Thatis, the point of the needle will swing Over i
. The railroad and engineering journal . the column of mercury will stand just 30 in. high in thetube. As we rise above the sea-level the pressure of theair grows less, and the column of mercury falls. In roundnumbers the mercury falls i in. for each 1,000 ft. we rise;so that, knowing this, we can tell approximately how high pends upon the diameterof the circle. In a 5-in. barome-ter the needle is 3 in, long, and the diameter of the circleis the same. In this case, the length which correspondsto I in. of the mercurial barometer is about \]i in. Thatis, the point of the needle will swing Over i . in. of arc LXI. No. ENGINEERING JOURNAL. 550 for the same change of atmospheric pressure that wouldmove the mercury up or down i in. in the mercurial ba-rometer; and this corresponds 10 about ft. changein elevation of the instrument. Thus this Ii in on the diviied circle, which is called aninch, corresponds in round numbers to a dilTerence of ele-vation of 1,000 ft. This inch is divided into 10 equal parts, each repre-senting 1
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectrailroa, bookyear1887
