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follows a description of Charts, with the methods of using and constructing them. The art of Surveying Coasts and Harbours, being very essential to those who visit unknown parts, is treated in a manner which it is hoped will make its acquisition and practice perfectly easy.

We come next to the application of Astronomy to Navigation, and here I have thought proper to give a short but comprehensive view of the solar system, where the Earth is considered as a Planet ; and have then described the various imaginary circles of the sphere. The nature of parallax, refraction, &c., are explained under this head. The Theory of the Winds and Tides, with the methods of finding the Time of High Water, follow next in order.

The most approved Methods of ascertaining the Latitude and Longitude at Sea by Celestial Observations, also the Variation of the Compass by Amplitudes and Azimuths, are explained by proper rules and examples ; there is also given a particular description, with the uses of the various Astronomical Instruments employed in taking the observations. In this part of the work I have given Mr. Douwes' Rules for computing the Latitude by two Altitudes of the Sun, and four different methods of clearing the Distance, the last of which, invented by Captain Mendoza Rios, has the advantage of not requiring any distinction of cases. The method of finding the Longitude by a Time-keeper being now much practised, the necessary rules and examples are introduced for that purpose.

The learner is next led into the Rules for keeping a Journal at Sea, wherein are exhibited the Methods of correcting the Courses for Leeway, Variation, &c., with general Rules for working a Day's Work; and the whole is illustrated by separate days' works, and further by a Journal kept from England to Madeira.

The Explanation of Sea Terms and Technical Phrases, also the substance of an Examination of a Young Sea Officer in the working and of piloting a Ship, I have inserted because, although they may be considered by some as superfluous, and not immediately connected with the subject, they nevertheless appeared to be of too much importance to others to be omitted.

With respect to the Tables in this Work, I have only to observe here, that they are published under the title of “ Nautical Tables,” that they have been very generally adopted by the Officers in the Navy and in the Honourable East India Company's Service, and have received the approbation of Navigators in general.

J W. NORIE.

NOTE.-It may here be observed that Norie's Complete Epitome of Practical Navigation was originally dedicated by permission “ to the Honourable the Court of Directors of the United Company of Merchants of England trading to the East Indies."

PREFACE TO THE NEW EDITION

This latest edition of this Epitome has been necessitated by a combination of circumstances, which need no description, but which are well known to students of Navigation.

The inclusion of so much "new work” together with the remodelling of a large portion of the old, afforded an opportunity of rearranging the book in a more systematic manner, having due regard to the order in which the various subjects fit into each other, and also to the order in which the young student of Navigation might, with advantage, pursue his studies.

It will be observed that those portions of the “ Science of Navigation." which have always been regarded as advanced have been placed towards the end of the book, as it was felt that to place too many difficulties in the early part of the work often resulted in the complete neglect of the whole subject by the young student at sea, who is thrown entirely on his own resources when in pursuit of knowledge.

This work must be regarded as a Standard Work on Navigation rather than a book for cramming purposes, and the student who goes diligently through it will be amply rewarded by a thorough knowledge of the theory and practice of Navigation, which no system of cramming can achieve.

The following new sections have been inserted in this edition: (I) Spherical Trigonometry (Napier's Rules for the solution of Right-angled and Quadrantal Spherical Triangles); (2) Figure Drawing in Nautical Astronomy; (3) Marine Surveying ; (4) Chart Construction; (5) Theory of the Station Pointer and its use; (6) Barometer, Thermometer, and Hydrometer ; (7) Reduction to Soundings; (8) Meteorology ; (9) Deviation of the Compass and Compass Adjustment; and lastly Proofs of certain Formula.

The following sections have been entirely remodelled and improved : (1) Logarithms; (2) Geometry; (3) Description and Use of Charts; (4) The Compass ; (5) The Sextant; (6) Introduction to Nautical Astronomy; 6) Correction of Courses; (8) Day's Work ; (9) Latitude by Reduction to the Meridian (Direct Method); (10) Computation of Altitudes; (11) Latitude by Double Altitudes (Direct Method); (12) Great Circle Sailing.

By the addition of the Natural Haversine Table to Norie's Nautical Tables, where it will be found adjacent to the Log. Haversine, it has been found possible to replace some very tedious and cumbersome calculations by equally sound but much shorter methods. This will be made obvious by an examination of the last method given in the Chronometer Problem, and also in the Computation of Altitudes, and Latitude by Double Altitude problems, where its advantages are fully exemplified.

It is earnestly recommended that the young student of Navigation should study at an early stage the principles of Plane Trigonometry, and also the application of Napier's Rules for Circular Parts to the solution of right-angled spherical trigonometry.

The practical use of Napier's Rules for Circular Parts is fully demonstrated in the Ex-Meridian, Latitude by Double Altitudes of a Star, and Great Circle Sailing problems.

My thanks are due to Mr. W. R. Courtney for the very able manner in which he has assisted me in reading the proofs of this very extended Epitome.

J. W. SAUL. London, July, 1917.

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CONTENTS

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INTRODUCTION

TABLES USEFUL IN NAVIGATION AND NAUTICAL ASTRONOMY

ARITHMETIC OF NAVIGATION

3

Addition, Subtraction, Multiplication, Division, and Reduction, of Degrees and Time.

DECIMAL ARITHMETIC

7

Addition, Subtractioe, Multiplication, Division, Reduction, and Proportion or Rule of

Three.

LOGARITHMS

Construction of and Examples; to find the Logarithm of any Number; to find the

Number corresponding to a given Logarithm; Multiplication, Division, Involu-

tion, Evolution, and Proportion.

GEOMETRY

Definitions, Sines, Tangents, Secants, etc.

GEOMETRY

Problems, Scales of Equal Parts; Lines of Chords, Rhumbs, Tangents, Sines, etc.;

to lay off and measure an Angle, etc.

PLANE TRIGONOMETRY

Right-Angled Trigonometry ; Definitions and Principles

Ratio; Trigonometrical Tables, etc.

Trigonometrical Functions of an Angle

Rules for computing the Angles and Sides of Right-Angled Triangles

Oblique-Angled Trigonometry

Application of Trigonometry to the Admeasurement of Heights and Distances, etc.

SPHERICAL TRIGONOMETRY

62

Napier's Rules for the Solution of Right-Angled Spherical Triangles; Quadrantal

Spherical Triangles.

FIGURE DRAWING

68

GEOGRAPHY AND NAVIGATION

74

Definitions ; Figure and Magnitude of the Earth ; Dimensions of the Earth ; Defini-

tions Relating to the Earth-as Axis, Poles, Equator, Meridians, Latitude,

Longitude, Horizon, Zones, etc.

Difference of Latitude ; Latitude Left; Latitude In ; Middle Latitude

78

Difference of Longitude; Longitude Lest; Longitude In, etc.

80

MARINE SURVEYING

Instruments; How to Survey a Bay, Coast or Harbour, with Examples and Plans,

CHART CONSTRUCTION

93

Natural Scales ; Method of Constructing a Mercator's Chart.

DESCRIPTION AND USE OF CHARTS

Finding the Latitude and Longitude of a Place ; To Mark the Ship's place on a Chart;

To Find the Course or Bearing, and the Distance between any two Places on a

Chart, etc.; Cross Bearings; the Four-Point Bearing and Doubling the Angle

on the Bow; Vertical and Horizontal Danger Angles; the Deviation Card and

its Use, etc.; Closing Remarks on Chart Work; Conventional Signs and

Symbols, etc.

THE STATION POINTER : Description and its Use

117

THE CHRONOMETER

THE COMPASS

128

The Liquid or Spirit Compass; The Gyroscope as a Compass; The Mariner's Com-

pass ; Divisions of the Compass Card into Points and Degrees; Compass Bowl ;

Binnacle, etc.; The Course ; Rhumbs; Steering Compass; Azimuth Compass ;

The Standard Compass; Dead Reckoning, etc,

THE HYDROMETER

THE TIDES

Time of High Water by Admiralty Tide Tables ; Reduction to Soundings; Reduction

to Soundings Examples; The Lead; Sounding Ma

LOG-SHIP AND LOG-LINE, WITH THE LOG-GLASS AND PATENT LOG; Length of a

Nautical Mile

METEOROLOGY

General Notices, Concise Rules for Revolving Storms.

OCEAN CURRENTS

INTRODUCTION TO NAUTICAL ASTRONOMY

Nautical Astronomy; Definitions and Principles; The Solar System and Fixed

Stars; Preliminary Definitions ; Definitions appertaining to Nautical Astronomy;

Definitions relating to Time and its Measures ; Apparent, Mean and Sidereal

Time ; Equation of Time; Civil and Astronomical Day; Greenwich Date, etc.

LONGITUDE AND TIME

THE NAUTICAL ALMANAC AND ASTRONOMICAL EPHEMERIS

The Nautical Almanac, 1914 Edition ; To find the Declination of the Sun at the

time of its transit over a given Meridian, also the Equation of Time at the same

instant; To find the Declination and Right Ascension of the Moon, at any given

Greenwich date ; To Correct the Sun's Declination by Second Differences; To

Correct the Equation of Time by Second Differences; To Correct the Moon's

Declination and Right Ascension by Second Differences; For the Correction of

the Declination or Right Ascension; To find the local time of the Moon's

Meridian Passage ; To find a Planet's Right Ascension and Declination at the

time of transit over a given Meridian; Moon's Semi-diameter and Horizontal

Parallax ; Planet's Right Ascension and Declination for a given Greenwich

Date, Mean Time ; To find the Right Ascension of the Mean Sua for a Given

Time and Place; The Right Ascension and Declination of the Fixed Stars.

CORRECTIONS OF OBSERVED ALTITUDES

The Index Error, Dip (or depression) of the Horizon, Refraction, Semi-Diameter and

Parallax ; Summary of the Corrections of Observed Altitudes; Corrections for

Sun, Moon, Planet, and Fixed Stars ; Zenith Distance; Corrections of Altitude

observed by an Artificial Horizon on Shore; Reduction of Altitude for Change

of Ship's Position, etc.

CONVERSION OF TIMES

Intervals of Mean, Apparent or Sidereal Time; To Convert Apparent to Mean

Time and vice versa ; To Convert Greenwich Mean Time into Sidereal Time at

Greenwich ; To Convert. Mean Time at a given Place into Sidereal Time at that

Place; To Convert Apparent Time at a given Place into Sidereal Time at that

Place; To Convert Sidereal Time at Place (or the Right Ascension of the Meridian)

into Mean Time at Place; Meridian Passage of the Sun and of a Fixed Star;
Given the Mean Time at a Place, to find what Principal Stars are East and West

of the Meridian; Hour-Angle of a Fixed Star.

SPECIFIC GRAVITY AND MISCELLANEOUS CALCULATIONS

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