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TABLE OF CONTENTS.
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.—Instru-
ments used for observing Angles on the Continent and in England.—Re-
duction 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
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 Com-
pass.-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 Rail-
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
I. TO CONVERT SIDEREAL TIME INTO MEAN SOLAR TIME, AND THE REVERSE 173
II. TO DETERMINE THE AMOUNT OF THE SEVERAL CORRECTIONS FOR
III. TO DETERMINE THE LATITUDE.
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
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-
V. TO DETERMINE THE LONGITUDE.
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.
3. By equal Altitudes and Azimuths.
4. By a Transit Instrument when properly adjusted in the Plane of the