. Elements of theoretical and descriptive astronomy, for the use of colleges and academies. connecting the central points of the pivots. The axis of collimation is an imaginary line drawn from theoptical centre of the object-glass, perpendicular to the axis ofrotation. The line of sight is an imaginary line drawn from the opticalcentre of the object-glass to the middle wire. The transit instrument is accurately adjusted in the plane ofthe meridian, when the line of sight of the telescope lies in that plane, as the telescope revolves. Three things,then, are readily seen to be neces
. Elements of theoretical and descriptive astronomy, for the use of colleges and academies. connecting the central points of the pivots. The axis of collimation is an imaginary line drawn from theoptical centre of the object-glass, perpendicular to the axis ofrotation. The line of sight is an imaginary line drawn from the opticalcentre of the object-glass to the middle wire. The transit instrument is accurately adjusted in the plane ofthe meridian, when the line of sight of the telescope lies in that plane, as the telescope revolves. Three things,then, are readily seen to be necessary: the axis of rotation mustbe exactly horizontal; it must lie exactly east and west; and theline of sight and the axis of collimation must exactly , these conditions are rarely fulfilled; but they can, byrepeated experiments, be very nearly fulfilled, and the errorswhich the failure rigorously to adjust the instrument causes inthe observations will be constant and small, and can be accu-rately principal application of the transit. THE MERIDIAN CIRCLE.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectastrono, bookyear1901
