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TABLE OF CONTENTS.

CHAPTER I.

GENERAL OUTLINE OF THE SYSTEM OF CARRYING ON A TRIGONOMETRICAL

SURVEY

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CHAPTER II.

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.

CHAPTER III.

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

Stations also ascertained by astronomical Observation

CHAPTER IV.

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 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-

ways

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CHAPTER V.

MILITARY RECONNAISSANCE AND HINTS ON SKETCHING GROUND.

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

Enemy's Works.-Conventional Signs.

CHAPTER VI.

LEVELLING.

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

Contoured Plans .

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CHAPTER VII.

LEVELLING CONTINUED.

Method of ascertaining Altitudes with the Mountain Barometer.—

Aneroid.-Substitute for the Barometer.-Determination of Altitudes by

the Temperature of Boiling Water

CHAPTER VIII.

SHADING AND ENGRAVING TOPOGRAPHICAL PLANS.

Vertical Disposition of Light-Oblique Light.-Objections to this

Method. Conventional System, partaking of both.-Anaglyptograph

Engraving

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CHAPTER IX.

COLONIAL SURVEYING.

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-

formation to be obtained

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CHAPTER X.

GEODESICAL OPERATIONS CONNECTED WITH A TRIGONOMETRICAL

SURVEY.

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

adapted to limited portions of the Globe

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CHAPTER XI.

PRACTICAL ASTRONOMY.

Sextant and Repeating Circle, &c.-Definition of Terms.-Division of

Time.-Solar and Sidereal Day.-Observations of the Sun and Stars .

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PROBLEMS.

I. TO CONVERT SIDEREAL TIME INTO MEAN SOLAR TIME, AND THE REVERSE 173

II. TO DETERMINE THE AMOUNT OF THE SEVERAL CORRECTIONS FOR

REFRACTION, PARALLAX, &c.

III. TO DETERMINE THE LATITUDE.

1. By Observations of a circumpolar Star at the time of its Upper and

Lower Culminations.

2. By Meridional Altitudes of the Sun, or a Star whose declination is known, involving the Reduction to the Meridian.

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-

tween the Observations

V. TO DETERMINE THE LONGITUDE.

1. By the Comparison of local Time with that shown by a Chronometer from

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

Moon.

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 and Azimuths.

4. By a Transit Instrument when properly adjusted in the Plane of the

Meridian

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