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TABLE OF CONTENTS.
CHAPTER I. GENERAL OUTLINE OF THE SYSTEM OF CARRYING ON A TRIGONOMETRICAL SURVEY
MEASUREMENT OF A BASE LINE.
Description of the different Methods that have been adopted to ensure its correct Measurement.—Combined Iron and Brass Rods used on the Ordnance Survey.-Visual Contact with reading Microscopes.-Reduction of a Base measured on any elevated Plain to its Value at the Level of the Sea.-Prolonging and verifying a Measured Base by Triangulation.
TRIANGULATION. Choice of Stations.—Method of rendering distant Stations visible-by Reflection of the Sun's Rays-Argand Burners-Drummond's Light.Method of increasing the Length of the Sides of the first Triangles directly from the Measured Base.—Secondary Triangles.-Assumed Base.—Instruments used for observing Angles on the Continent and in England.-Reduction to the Horizon.-Spherical Excess.-Reduction to the Centre.Adjustments of a Theodolite.—Method of discovering lost Stations.Laying down a Triangulation upon Paper.—Position of Trigonometrical Stations also ascertained by astronomical Observation
INTERIOR FILLING-IN OF A SURVEY, EITHER ENTIRELY OR
PARTIALLY, BY MEASUREMENT. Method of Filling-in the Detail entirely by Measurement, as practised on the Ordnance Survey.—Levelling Marks and Forms of Field-Books, &c.— Measurement of Roads by the Chain and Theodolite.-Computing the Contents of Enclosures directly from the Field-Book.--Filling-in the Interior, partly by Sketching.-Road Surveying.–Variation of the Compass.—Sketching between Trigonometrical Points and Measured Lines.Practical Methods of avoiding Obstacles and determining inaccessible Heights and Distances in the Field.-Station Pointer.-Surveys for Railways
Correction for Curvature of the Earth—for Refraction.—Average
2. By Veridional Altitudes of the Sun, or a Star whose declination is
known, involving the luction to the Meridian.
6. By Transit Observations on the Prime Vertical
IV.-TO FIND THE LOCAL TIME.
which the Time at some fixed Meridian is known.
2. By Signals.
3. By the Transmission of Chronometers between Stations.
4. By the Eclipses of Jupiter's Satellites, and the Eclipses of the Sun and
5. By Lunar Observations.
6. By the Method of Moon-culminating Stars.
7. By Occultations of fixed Stars by the Moon
VI.-TO FIND THE DIRECTION OF A MERIDIAN LINE, AND THE VARIATION
OF THE COMPASS.
1. By the Azimuth of any Celestial Object.
2. By the Amplitude of the Sun at his rising or setting.
3. By equal Altitudes ard Azimuths.
4. By a Transit Instrument when properly adjusted in the Plane of the
TABLES OF USE IN THE FOREGOING PROBLEMS.
7. Augmentation of semi-diameter of the Moon, with her increase in
9. Reduction of the Moon's equatorial horizontal parallax for any