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NAVIGATION

AND

NAUTICAL ASTRONOMY.

PART I.

CONTAINING

RULES FOR FINDING THE LATITUDE AND LONGITUDE, AND THE
VARIATION OF THE COMPASS.

With numerous Cramples.

By H. W. JEANS, F.R.A.S.

ROYAL NAVAL COLLEGE, PORTSMOUTH;

Author of a Work on "Plane and Spherical Trigonometry;" "Handbook of the Stars;"
"Problems in Astronomy, Navigation, &c. with Solutions:" formerly Mathematical
Master in the Royal Military Academy, Woolwich; and an Examiner of Officers in the
Merchant-Service in Nautical Astronomy, &c.

LONDON:

LONGMAN, BROWN, GREEN, AND LONGMANS.
1858.

184. C. 18.

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PREFACE.

THIS volume of practical rules and examples will be followed by a theoretical treatise on Navigation and Nautical Astronomy, to be called Part II. It will be the aim of the author, in the forthcoming work, to investigate some of the principal rules and corrections in Nautical Astronomy; but in order to simplify the subject as much as possible, Part II. will be made to consist only of such investigations as require in the student nothing beyond a knowledge of Trigonometry: and only the most simple of these investigations will be selected. Therefore the demonstrations of the rules for finding the longitude by occultations, by solar eclipses, transits, &c., as well as the explanation of refraction, of precession, interpolation, &c., and of certain methods for determining the latitude and longitude, which from the peculiar elegance of the artifices used are instructive, and deserve the consideration of the student, -not being of general use, will in Part II. be omitted. They may hereafter be collected and formed into a separate volume, as Part III.

To the present volume is added a rule for finding the time of high-water it has been now introduced into the book chiefly for students who use Inman's Tables only.

No rule is given in this volume for finding the latitude by pole-star; the one in the Nautical Almanac, a work which every naval student is supposed to possess, being deemed suf

ficient. Examples are given for finding the latitude by the altitude of the pole-star in the College Examination-Papers at the end of the volume.

Another important and very necessary addition will be found in the page of errata. To obtain this, the examples have been recalculated, and the author trusts the principal errata have been discovered: still, in a work like the present, in which so many thousand figures must be used to obtain the answers, it is difficult to avoid mistakes; and it is only after several revisions that a near approach to correctness can be made.

ROYAL NAVAL COLLEGE,

October 21, 1857.

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of bearing at.

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{ after correction, add +2′ 42′′ and height of eye

above the sea.

alter latitudes

to

b.

meridian

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99

the correction 4′ 38′′ should be added: the correct latitude will then be 54° 53′ 21′′ N.

99

altitudes.

equator.

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