DIY History | Transcribe | Scholarship at Iowa | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903 | Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 18

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Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no.26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903

Theory of the astronomical transit instrument applied to the portable transit instrument Wuerdemann no. 26: a compilation from various authorities, with original observations by Harry Edward Burton, 1903, Page 18

and again read the scale. The first readings are [?called] direct and the second [?] If this adjustment is perfect the difference of the two east (or west) and readings will be [?] for a [?] numbered in both directions from the middle. If the adjustment is not perfect, one half the difference of the two east (or west) readings must be corrected by raising or lowering one end of the tube. Repeat the process until the adjustment is satisfactory. The [V's?] of the level should rest only on the pivots. Rock the level slightly to see that the {V's?] don't touch the Y's at any point. 
Second the vertical plane passed thru the axis must be parallel to that passed thru the tube. Let the level be rocked back and forth on the pivots of the axis. If the reading changed in consequence of this motion, the adjustment is not perfect. The direction in which the side adjusting [?] must be moved will appear from the motion of the bubble. The first adjustment should afterwards be examined as it may have been disturbed by this operation.

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and again read the scale. The first readings are [?called] direct and the second [?] If this adjustment is perfect the difference of the two east (or west) and readings will be [?] for a [?] numbered in both directions from the middle. If the adjustment is not perfect, one half the difference of the two east (or west) readings must be corrected by raising or lowering one end of the tube. Repeat the process until the adjustment is satisfactory. The [V's?] of the level should rest only on the pivots. Rock the level slightly to see that the {V's?] don't touch the Y's at any point. Second the vertical plane passed thru the axis must be parallel to that passed thru the tube. Let the level be rocked back and forth on the pivots of the axis. If the reading changed in consequence of this motion, the adjustment is not perfect. The direction in which the side adjusting [?] must be moved will appear from the motion of the bubble. The first adjustment should afterwards be examined as it may have been disturbed by this operation.