CHAPTER VIII.

SURVEYS FOR WATER SUPPLY WORKS.

General Features of Water Supply Surveys-Parliamentary Survey-

Survey of Reservoir and Cross Sections-Cross and Longitudinal

Sections of Embankment-Extent of Cross Sections and "Top

Water Level"-Plan of Reservoir-Plan of Embankment-Longi-

tudinal Section of Reservoir-Fence Line and other Details-

Byewash-Line of Pipes-Aqueduct or Open Conduit--Service

Reservoir and Filters-Working Survey and Pegging out-Example

of Survey of Reservoir -

CHAPTER IX.

PAGES

311-316

HYDROGRAPHICAL OR Marine surVEYING.

Instruments: Sextant-Determination of the Shore Line and High and

Low Water Marks: Survey of Coast Line-" Running Survey "

from the Ship-Surveys for Docks and Harbours-Soundings:

Sounding Lines and Rods-Taking and fixing Position of Soundings

-The "Three Point Problem "-The Station Pointer-Geometrical

and Analytical Solutions of the Three Point Problem-Geometrical

Solution Analytical Solution - Check Angles - Location from

Compass Bearings to two Points only-Location of Point by

Simultaneous Observations with two Theodolites-Soundings in

Rivers or Narrow Waters-River Surveys-Running Survey of

200 Miles of River Nile-Datum-Bench Marks-Tide Gauges-

Reduction of Soundings - Currents - Current Meter - Signals,

Beacons, Buoys-Additional Details to be shown on Plans

-

CHAPTER X.

317-330

ASTRONOMICAL OBSERVATIONS USED IN SURVEYING.

Instruments: The Sextant-Adjustments of the Sextant-To make the

Index Glass Perpendicular to the Plane of the Arc-To make the

Horizon Glass Perpendicular to the Plane of the Arc-To make

the Line of Collimation of the Telescope Parallel to the Plane of

the Arc-To see if the two Mirrors are Parallel when the Index is

at Zero-Practical Hints in observing with the Sextant—Parallax

of the Sextant-Artificial Horizon-To observe very small Angles

with the Artificial Horizon-Observing Angles with Artificial

Horizon-Oblique Angles measured with Sextant-To reduce

an Oblique Angle to its Horizontal Projection-The Advantages

of the Sextant Necessity for Astronomical Observations-

Observations for Meridian-Meridian by two greatest Elongations

of a Circumpolar Star-Meridian by Equal Altitudes of a Circum-

polar Star-Example of finding Meridian by Equal Altitudes of

Circumpolar Star-Meridian by Equal Altitudes of the Sun-

-

Latitude and Longitude by Account--Rule- Meridian by two

Stars at Elongation-Meridian by Observation of one Circum-

polar Star at Elongation-Example of finding Meridian by Obser-

vation of one Circumpolar Star at Elongation—To Calculate the

Time of a Star's Culmination or Elongation-Example of Calcula-

tion of Time of Star's Culmination-Calculation of Star's Altitude

at Elongation-Meridian by observing the Pole-star and Alioth

in same Vertical-Meridian by observing Circumpolar Stars in

same Vertical-Test of Meridian by Time Interval between

Transits of Circumpolar Stars-Meridian by one Extra Meridian

Observation of Sun or Star-Errors in Calculated Azimuth by Sun

Observation due to given Errors in Latitude and Declination-

Example of finding Meridian by Extra Meridian Observation of

Sun-Coaltitude-Colatitude-Codeclination-Accuracy of Extra

Meridian Observation of Sun or Star-Calculation when either

Altitude, Latitude, or Declination is not known-Altitude not

known Latitude not known Declination not known-Con-

vergence of Meridians-Observations for Latitude-Latitude by

Meridian Altitude of Sun or Star-In the Northern Hemisphere

-In the Southern Hemisphere-Latitude by Meridian Altitude

of Sun-Example of finding Latitude by Meridian Altitude of

Sun-Latitude by Zenith Pair Observations of Stars-Latitude

by Extra Meridian Observations of Sun or Star-Prime Vertical

Observations for Latitude-Observations for Time --Approximate

Method of finding Time and Meridian-Time by Meridian Transit

of Sun or Star-Time by Extra Meridian Observation of Sun or

Star-To Convert Arc to Time and vice versa-To. Convert

Sidereal Time to Mean Time and vice versâ—Equation of Time—

Observations for Longitude-Longitude by Chronometer-Deter-

mination of Difference of Longitude by Watch-Example of find-

ing Difference of Longitude by Watch-Longitude by Absolute

Methods-Longitude by Eclipses of Jupiter's Satellites-Longi-

tude by Moon Culminating Stars-Longitude by Lunar Occultations

-Longitude by Lunar Distances-Solution of Spherical Triangles

-Right-angled Spherical Triangles-Oblique Spherical Triangles

-Rule of Sines-Reduction of Sides of Spherical Triangles to

Actual Linear Distances

PAGES

331-387

APPENDIX.

EXPLANATION OF ASTRONOMICAL TERMS IN

CHAPTER X.

Altitude-Apparent Time-Astronomical Mean Time-Azimuth-Cir-
cumpolar Stars-Civil Mean Time-Coaltitude-Codeclination —
Colatitude-Contraction-Conjunction-Culmination― Declination
— Elongation — Equation of Time-Equator - Great Circle-

Horizon-Hour Angle-Latitude-Limb-Longitude-Local Mean

Time

Meridian-Occultation-Parallax-Polar Distance-Poles-

Prime Vertical-Refraction-Right Ascension-Sidereal Time—

Spherical Angle-Zenith-Zenith Distance

CHAPTER XI.

PAGES

388-392

SURVEYS ABROAD IN JUNgle, dense forest, and

UNMAPPED OPEN COUNTRY.

Surveys for a Long Line of Communication, such as a Road or Railway,

&c.-Reconnaissance or Exploration of various Proposed Routes-

Reconnaissance in Open Country-Reconnaissance in Thick Jungle

or Dense Forest-Route Survey or Trial Location-Route Survey

or Trial Location in Open Country-Route Survey or Trial

Location in Jungle or Dense Forest-Preliminary Location Survey

on Route Selected-Final Location Survey and Setting out of

Line-Scales-Distance and Bearing of Objective Point of a Long

Traverse or Straight Line-Distance and Bearing of Objective

Point from Intermediate Point of Traverse-Running a Long

Straight Line-Checking Traverse by Bearings to Lateral Objects—

Classification of Curves by "Degree ". American Method of

Cross Sectioning-Surveys of a Limited Area of Country-Methods

to be adopted-Steel Tape Measurements-Example of Survey-

Regulations of the Victoria Survey Department, Australia—Sur-

veying Regulations in the Australian Colonies-Subjects of Ex-

amination of "Authorised" Surveyors to Lands Departments,

Colony of Victoria, Australia

---

CHAPTER XII.

393-422

TRIGONOMETRICAL OR GEODETIC SURVEYS.

Ordinary Small and Large Surveys--Trigonometrical Survey-Base

Line and Primary Triangles-Base of Verification - Secondary

Triangles-Tertiary Triangles-Interior Filling-in-Triangulation

Stations-Whole Survey Reduced to Sea Level-Base Lines of the

Ordnance Survey of Great Britain and Ireland-Hounslow Heath

Base-Romney Marsh Base of Verification-Salisbury Plain Base

of Verification-King's Sedgemoor Base-Misterton Carr Base-

Rhuddlan Marsh Base-Method adopted for Measuring Base Lines

--Base on Shores of Lough Foyle, Ireland: Colonel Colby's Base-

measuring Apparatus-United States Coast and Geodetic Survey

Base-measuring Apparatus-The Great Theodolite of the United

States Coast and Geodetic Survey-The Great Theodolite of the

Ordnance Survey-Portable Scaffold-Portable Signal-Portable

Crane-Permanent Station Marks-12 in. Theodolite of the

Ordnance Survey-7 in. and 5 in. Theodolites of the Ordnance

Survey-Triangles of the Ordnance Survey of Great Britain and

Ireland-Primary Triangles-Secondary Triangles-Tertiary Tri-

angles-General Form of Triangulation-Reconnaissance and

Selection of Stations-Determining necessary Heights of Stations-

Clearing out Line between two Stations not visible from each

other-Selection of Base Lines-Permanent Marking of Stations

and Base Lines-Instrument Stations and Scaffolds—Signals—

Sun Signals or Heliographs and Heliostats-Heliostats and Helio-

graphs-Gauss' Heliotrope-Wharton's Improvised Heliostat-

Night Signals-Phase of a Signal-Measurement of Base: Measure-

ment with Steel Tape—Straining Apparatus—Absolute Length of

Tape-The Coefficient of Expansion-The Modulus of Elasticity-

Correction for Sag-Correction for Pull-To Eliminate Corrections

for Sag and Pull-Correction for Temperature-Corrections for

Fractional Part of Tape Length-Measurement of Bases with

Steel and Brass Wires-Accuracy of Steel Tape Base Measure-

ments-Measurement with Rods-Broken Base-Reduction of

Base to Horizontal-Reduction of Base to Mean Sea Level-

Extending a Base-Extension of the Triangulation from the

Measured Base-Instruments-Observation of the Angles: Method

of Repetition-Method of observing Horizontal Angles adopted on

Ordnance Survey of United Kingdom-General Method of observ-

ing Angles-Time for observing Angles-Accuracy of Measure-

ments of Angles-Reduction of Angles to the Centre of Station-

Correction of the Errors of the Angles-Calculation of Spherical

Excess-Adjustment of the Angles-Example of Correction and

Adjustment of Angles of a Triangle-Correction by Reciprocals

of Number of Observations-Correction by Reciprocals of Squares

of Number of Observations-Adjustment of Angles inversely as

"Weights" of Observations-Calculation of the Sides of the

Triangles-Calculation by Spherical Trigonometry-Calculation

by Delambre's Method-Calculation by Legendre's Method--

Summary of Operations in Computation of Triangles by Legendre's

Method - Calculation of the Astronomical Co-ordinates of the

Stations-Polar Spherical Co-ordinates — Rectangular Spherical

Co-ordinates-Surveying of Interior Detail-Levelling-Cost of

Trigonometrical Surveys-Instructions for Secondary Triangulation

-Locating Stations-Reading Angles-Closing Triangles-Base

Lines-Observations for Azimuth-Stone Line Bench Marks-

Cutting Timber-Descriptions of Stations-Tertiary Triangula-

tion - Triangles - Stations Instrument Stations - Observing

Angles-Marking Stations-Map Projections-Projection to be

adopted — Rectangular Projection — Trapezoidal Projection

Simple Conic Projection-De L'Isle's Conic Projection-Bonne's

Projection—The Polyconic Projection-Projection of Maps of the

Survey of India-Projection of Maps of the Ordnance Survey of

the United Kingdom

PAGES

423-481

LIST OF TABLES.

PAGES

TABLE I. FOR HEIGHTS BY MERCURIAL BAROMETER 168, 482, 484, 485

III. FOR HEIGHTS BY BOILING POINT THERMOMETER 171, 494, 497

IV. FOR REDUCTION OF INCLINED SIGHTS IN TACHEO-
METRY OR STADIA SURVEYING

- 273, 498

TABLE FOR REDUCING MEASUREMENTS ON SLOPE TO HORI-
ZONTAL, 66 FT. CHAIN

9

TABLE FOR REDUCING MEASUREMENTS ON SLOPE TO HORI-
ZONTAL, 100 FT. CHAIN

IO

TABLE FOR CONVERSION OF DEPARTURE INTO DIFFERENCE of
LONGITUDE

348

TABLE OF LENGTHS OF A DEGREE OF LONGITUDE At Different

LATITUDES

349