A Manual of Spherical and Practical Astronomy: Embracing the General Problems of Spherical Astronomy, The Special Applications to Nautical Astronomy, and the Theory and Use of Fixed and Portable Astronomical Instruments. With an Appendix on the Method of Least Squares. By William Chauvenet. Vol. II. Theory and Use of AStronomical Instruments. Method of Least Squares. CONTENTS OF VOL. II. Theory and Use of Astronomical Instruments. CHAPTER I. The Telescope. Magnifying power measured. CHAPTER II. Of the Measurement of Angles or Arcs in General-Circles-Micrometers-Level. Graduated circles. The vernier. The reading microscope. Eccentricity of graduated circles. Periodic functions. Ellipticity of the pivot of the alidade. Errors of graduation. The filar micrometer. The level. CHAPTER III. Instruments for Measuring Time. Chronometers. Comparison of chronometers. Clocks. The electro-chronograph. CHAPTER IV. The Sextant, and Other Reflecting Instruments. Description of the sextant. Adjustment of the sextant. Method of observation. Theory of the errors of the sextant. The simple reflecting circle. The repeating reflecting circle. Theory of its errors. The prismatic reflecting circle and sextant. CHAPTER V. The Transit Instrument. Description of the transit instrument. Method of observation. General formulas. The transit instrument in the meridian. Approximate adjustment. Equations of the transit instrument in the meridian. Thread intervals. Reduction to the middle thread. Reduction to the mean of the threads. Level constant. Collimation constant. Azimuth constant. Clock correction. Determination of the right ascension of stars. Transits of the moon, sun, and planets. Effect of refraction in transit observations. Meridian mark. Personal equation. Personal scale. Probable error of a transit observation. Application of the method of least squares to the determination of the time with a portable instrument in the meridian. The transit instrument in any vertical plane. Finding the time with a portable transit instrument out of the meridian Hansen's method. Application of the method of least squares to the determination of the time with a portable transit, instrument in the vertical circle of a circumpolar star Bessel's method. Determination of the geographical latitude by a transit instrument in the prime vertical. Determination of the declinations of stars by their transits over the prime vertical.