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TABLE OF CONTENTS.
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
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
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
Particular objects of a Reconnaissance under different circumstances.—
Method of commencing Military Sketch.-Portable Instruments best
adapted for sketching Ground.-Methods of delineating the fea-
tures of Ground with a Pen or Pencil.-Vertical System.-Horizontal.—
German Methods of producing a Mathematical Representation of the
Slopes of Ground by a "Scale of Shade," and also by a combination of
Vertical and Horizontal Lines-Horizontal Contours-Geological Features.
"Clinometer" for Measuring the Angles of Slopes.-Topographical
Sketches.-Judgment of Distances.-Military Reconnaissance of an
Correction for Curvature of the Earth-for Refraction.-Average
Amount of these Corrections.-Reciprocal Angles of Depression and
Elevation for determining the Amount of Refraction at any particular
period.-Method of taking Sections of Ground with a Theodolite.-Cross
Sections. Trial Sections.-Check Levels.-Spirit Level and its Adjust-
ments. French Water Level.-Boning Rods.-Reflecting Level.-Method
of taking Sections with the Spirit Level, or other Instrument adapted for
tracing Horizontal Lines.-Plotting Sections. Sectio-planography. —
Sections for Railways.-Method of Tracing Contour Lines.-System of
Contouring practised on the Ordnance Surveys.—Data afforded by Contour
Plans for determining the most available directions for Roads, Railways,
Lines of Drainage, &c.-Construction of Models.—Problems determined by
Method of ascertaining Altitudes with the Mountain Barometer.—
Aneroid.-Substitute for the Barometer.-Determination of Altitudes by
SHADING AND ENGRAVING TOPOGRAPHICAL PLANS.
Vertical Disposition of Light-Oblique Light.-Objections to this
Method. Conventional System, partaking of both.-Anaglyptograph
Difference between the Objects in view in the Survey of a Cultivated
and that of a new Unsettled Country.-First Operations.-Preliminary Ex-
ploration.-Objects to be principally considered.-Sites of Townships.—
Main Lines of Communication.-Guides for marking on the Ground the
Divisions of Properties.—Size of these Divisions.-Precautions to be ob-
served to secure to the Public Rights of Road, &c.-Necessity for Extensive
Surveys on the First Settlement of a New Colony.-Deviations from Gene-
ral Rules in laying out Sections.—Frontages on, and Access to Rivers and
Main Roads.-Sectional Roads.-Monopoly of Water to be guarded against.
-Sections laid out in Broken Irregular Ground.—Statistical and other In-
formation to be fully afforded to Settlers.-Marking Boundaries of Sec-
tions and Roads.-Reservation of Rights of Road.-Natural Features of
Ground.-Geological and Mineralogical Specimens, and Meteorological
Register, &c.-Usual Method of marking Regular Figures upon the Ground,
--Necessity for a Triangulation to conduct these Operations with any degree
of accuracy when upon an extended Scale.—Advantage of Carrying it on
rather in advance of the Sectional Surveys.-Other Uses of the Triangula-
tion.-District Surveyors.-Surveying by Contract.-Rate of Progress and
Cost per Acre of the Sectional Survey and Marking out Roads.-Cost of
the Triangulation.-Method of Survey pursued in the Canterbury Settle-
ment, New Zealand.-Temporary Division of Land for pastoral Purposes.
-Territorial Division of Counties, Hundreds, &c.—Remarks on Exploring
Expeditions. Method of Proceeding.-Objects in View, and collateral In-
Figure of the Earth.-Measurement of an Arc of the Meridian.—Of a
Parallel.-French Standard of weights and measures obtained from the
measurement of an Arc of the Meridian between Dunkirk and Barcelona.
-Popular Account of the method of conducting these Measurements.—
Correct determination of distance between two points whose latitude and
longitude are known.-Convergence of Meridians.—Radius of Curvature.—
Calculation of Azimuths as practised on the recent Survey of the North
American Boundary.-Latitude and Longitude of Stations with reference
to those of places already determined. Variation of the Compass, and
marking out a Meridian Line.-Projections of the Sphere.-Projection
Sextant and Repeating Circle, &c.-Definition of Terms.-Division of
Time.-Solar and Sidereal Day.-Observations of the Sun and Stars .
1. By Observations of a circumpolar Star at the time of its Upper and
2. By Meridional Altitudes of the Sun, or a Star whose declination is
3. By the Altitude of the Pole Star at any time of the day.
4. By an Altitude of the Sun, or a Star, out of the Meridian, the correct
time of Observation being known.
5. By two observed Altitudes of the Sun or a Star, and the interval of time
between them; or the difference, or sum of their Azimuths.
6. By Transit Observations on the Prime Vertical
IV.—TO FIND THE LOCAL TIME.
1. From single, or absolute, Altitudes of the Sun, or a Star whose declina-
tion, as also the latitude of the place of observation, are known.
2. By equal Altitudes of a Star, or the Sun, and the Interval of Time be-
1. By the Comparison of local Time with that shown by a Chronometer from
3. By the Transmission of Chronometers between Stations.
4. By the Eclipses of Jupiter's Satellites, and the Eclipses of the Sun and
6. By the Method of Moon-culminating Stars.
1. By the Azimuth of any Celestial Object.
2. By the Amplitude of the Sun at his rising or setting.
5. Contraction of semi-diameters of the Sun and Moon from Refraction
7. Augmentation of semi-diameter of the Moon, with her increase in
15. Length of a second of a degree of latitude and longitude
16. Corrections for curvature and refraction
17. Reduction upon each chain's length for different vertical angles
18. Ratio of slopes for different vertical angles