. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . SEDUCTION OF THE BAROMETRIC OBSERVATIONS. 59 made upon our line were developed into a curve ; the abscissa? representing the times of obser-vation, and the ordinates, corresponding readings, or rather fluctuations, of the barometer ; themeasured difference between the altitudes of any two ordinates being the true elevation ordepression of the mercurial column after all the known corrections had been applied. Thiscurve was found to be rem
. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . SEDUCTION OF THE BAROMETRIC OBSERVATIONS. 59 made upon our line were developed into a curve ; the abscissa? representing the times of obser-vation, and the ordinates, corresponding readings, or rather fluctuations, of the barometer ; themeasured difference between the altitudes of any two ordinates being the true elevation ordepression of the mercurial column after all the known corrections had been applied. Thiscurve was found to be remarkably regular, so long as the observations from which it was plottedwere made at the same station. But upon a change of place, the base being altered, the con-tinuity of the line was broken ; and observations made at the second station could not be com-pared with those taken a few hours before at the first, until the barometric movement for theintermediate time should be made known. This could be satisfactorily determined only byobservations upon a barometer at rest during that period. Upon inquiry, it was ascertainedthat, subsequent to our first com
Size: 1271px × 1967px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectdiscoveriesingeography, booksubjectn
