Elements of theoretical and descriptive astronomy, for the use of colleges and academies (1901)
White, Charles J · New York: J. Wiley & sons · leaf 37
o 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 coincide.Practically, these conditions are rarely fulfilled; but they can, byrepeated experiments, be very nearly fulfilled, and the… … THE MERIDIAN CIRCLE.
Astronomy
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