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accuracy accurate adjustment air column aneroid angle approximate aqueous vapor assumed atmos atmosphere backsight barome barometric formula barometric leveling base station boiling brass bubble cistern cloth coefficient of refraction computed deduced determined difference of altitude difference of elevation difference of level diurnal effect eleva eliminated ence equation equilibrium Errors due feet geodesic leveling Gilbert glass greater Guyot's Collection heat height horizontal hypsometric I—log inch increase instru instrument ivory point justment Lake Survey length of sight line of light line of sight lower station measured ment mercurial barometer meters method micrometer miles Mississippi River moisture mula Ordnance Survey perature phere Plantamour's preceding pressure reading the position scale screw servations source of error spirit level static equilibrium statical formulae stratum strument surface tables tance target telescope temperature temperature and humidity thermometer tical tion trigono trigonometrical leveling tube ture vacuum variation Williamson zenith distances
Сторінка 11 - B by means of four large screws P and the ring R ; on the ring R screws the cap S, which covers the lower parts of the cistern, and supports at the end of the adjusting screw O.
Сторінка 11 - ... up of a glass cylinder F, which allows the surface of the mercury q to be seen, and a top plate G, through the neck of which the barometer tube / passes, and to which it is fastened by a piece of kid leather, making a strong but flexible joint.
Сторінка 19 - The instrument can then be hung up and readjusted. The tube and its contents having been undisturbed, the instrument should read the same as before. If a little mercury has been lost during the operation, and there is none at hand to replace it, no serious harm has been done; but if much is lost, the open end of the tube may become exposed in inverting the instrument, in which case air may enter.