## A complete set of nautical tables |

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Page 352 - 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 lxxi - ... will be the right ascension of the meridian ; the difference between which and the right ascension of the object...

Page xlvi - 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.f EXAMPLE I.

Page xxvi - Amplitudes. This table is intended to expedite the method of finding the variation of the compass by comparing the magnetic with the true amplitude : the latter is here taken out by inspection, being given in degrees and minutes, and is to be found with the declination at the top, and the latitude in the left side column. Moreover, when the minutes of the latitude or declination are nearly 30, or half a degree, the mean of the amplitudes found for the two nearest degrees, will give the amplitude...

Page xcviii - ... of the third angle. 5. To the proportional logarithm of the correction of the moon's apparent altitude, add the logarithmic co-tangrnt of her apparent altitude, and the tangent of rhe diftance corrected for the fun or (tar's refraction ; their fum, rejecting^ 20 in the index, will be the proportional logarithm of the fourth angle.

Page lxxxvi - DBF the roof, in which are fixed two plates of glass, DE and EF, whose surfaces are plane and parallel to each other : and O the sun at S, whose altitude is required. Now the ray, SH, proceeding from the sun's lower limb to the surface of the quicksilver, will be reflected thence to the eye in the direction, HG, and the upper limb of the sun's image, reflected from the quicksilver, will appear in the line, GH, continued to R; and it is a wellknown principle in catoptrics, that the angle of incidence,...

Page lxxxv - ... the object) reflected from the index-glass, must be brought into contact with the opposite limb of the image reflected from the artificial horizon, observing that when the inverting telescope...

Page lvii - ... 4. Add together the secant of arc first, the sine of half the sum of the true altitudes, the cosine of half their difference, and the secant of arc third, and the sum, rejecting the tens from the index, will be the cosine of arc fourth.

Page xliii - ... or a table of the sun's declination, and mark whether it be north or south ; then, if the zenith distance, and declination have the same name, their sum is the latitude, but, if they have contrary names, their difference is the latitude, and it is always of the same name with the greater of the two quantities. EXAMPLES.

Page xxx - In the first place, the altitude of any star when passing the meridian, may be found by adding together the co-latitude of the place of observation and the declination of the star, when they are of the same name, or taking their difference when of contrary names ; the altitude to be reckoned from the south point of the horizon, when the latitude is north, and the contrary when south ; but when the sum exceeds 90°, it is to be taken from 180°...