## A complete epitome of practical navigation |

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### Contents

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### Common terms and phrases

angle arch Argo Navis centre chronometer Co-sec Co-sine Co-tan cºa compass cºn Corr correction corresponding Diff difference of latitude difference of longitude Dist Dist|Dep Ditto East East Point entr Equation ExAMPLE extent will reach feet given Greenwich mean horizon horizontal parallax index error Island Latitude and Departure LATITUDES AND LONGITUDES logarithm meridian altitude miles moon moon's apparent altitude Nautical Almanac nearest noon North º º º observed altitude observer's eye ºil ºn ºn ºº parallel passing the meridian perpendicular planet Port prime vertical radius refraction remainder right ascension Rock sails Secant seconds semidiameter sextant ship ship's Shoal side column sine South Point star star's subtracted Sun's declination sun's lower limb Suversed Table taken Tang tangent true altitude true distance true longitude variation West

### Popular passages

Page 170 - 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 215 - 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 12 - The logarithm of the root of a number is found by dividing the logarithm of the number by the index of the root.

Page 47 - TO THEIR DIFFERENCE ; So IS THE TANGENT OF HALF THE SUM OF THE OPPOSITE ANGLES ; TO THE TANGENT OF HALF THEIR DIFFERENCE.

Page 178 - 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 211 - ... 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 185 - 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 12 - 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 166 - 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...