## A complete epitome of practical navigation |

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### Contents

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### Common terms and phrases

added altitude angle Answer apparent apparent altitude arch bearing called Cape centre chart chronometer circle Co-sec Co-sine coast column compass contained Corr correction corresponding course degrees Diff Difference of Latitude difference of longitude direction Dist distance Ditto divided draw east equal Equation error EXAMPLE extent feet figures give given greater Greenwich half height hence horizon Latitude and Departure length less logarithm longitude lower limb mean measure meridian method middle miles minutes moon moon's natural nearest noon North object observed opposite parallax parallel passing perpendicular planet points radius reduce remainder right ascension Rule sails scale Secant seconds ship side sine South star Star's subtracted Sun's Sun's declination sun's lower limb suppose Suvers Table taken Tang tangent true altitude variation Versed West

### Popular passages

Page 146 - Centigrade is equal to j of Reaumur. Multiply the given number of degrees of the Centigrade by 4, and divide the product by 5 ; the quotient will be the equivalent number of degrees on Reaumur's scale.

Page xx - LV. contains the times of high water on the full and change of the moon, with the vertical rise of the tide, at many ports, harbors.

Page 191 - If the true and magnetic amplitudes be both north or both south, their difference is the variation ; but if one be north and the other south, their sum is the variation; and to know whether it be easterly or westerly, suppose the observer looking towards that point of the compass representing the magnetic amplitude ; then, if the true amplitude be to the right hand of the magnetic, the variation is east, but if to the left hand, it is west.

Page 6 - The logarithm of the root of a number is found by dividing the logarithm of the number by the index of the root.

Page 41 - TO THEIR DIFFERENCE ; So IS THE TANGENT OF HALF THE SUM OF THE OPPOSITE ANGLES ; TO THE TANGENT OF HALF THEIR DIFFERENCE.

Page 154 - To set the glasses perpendicular to the plane of the quadrant there are two sunk screws, one before and one behind each glass: these screws pass through the plate on which the frame is fixed into another plate, so that by loosening one and tightening the other of these screws, the direction of the frame, with its mirror, may be altered, and thus be set perpendicular to the plane of the instrument.

Page 187 - ... east or west points of the horizon. The magnetic amplitude, is an arch contained between the east or west points of the compass and the centre of the object at rising or setting ; or it is the bearing of the object, by compass, when in the horizon. The true azimuth of an object is an arch of the horizon contained between the true meridian and the azimuth circle passing through the centre of the object.

Page 161 - Then, if the zenith distance and declination be both north or both south, add them together; but if one be north and the other south, subtract the less from the greater, and the sum or difference will be the latitude, of the same name with the greater.* EXAMPLE I.

Page 6 - Multiply the index of the quantity by the index of the power to which it is to be raised, and the result will be the power required.

Page 144 - Tides do not always answer to the same distance of the Moon from the meridian at the same places, but are variously affected by the action of the Sun? which brings them on sooner when the Moon is in her first and third quarters, and keeps them back later when she is in her second and fourth; because, in the...