A TABLE 11. Apparent Time of Transit of Pole Star. This table is adapted to leap year, particularly 1808. In order to make it serve for other years, the time of transit must be taken for the day following that given in the months of January and February. Far the first year after leap year, one minute is to be added to the time sí transit given in the table; two minutes for the second, and three minutes for the third after leap year, Again, to reduce this table to a different meridian than that to which it is adapted, viz. Greenwich; if the longitude is between 45° E, and - 45° W, there is no correction to be applied. If the longitude is between 45° and 135 E, one minute is to be added; but if it is between 45° and 135° W, one minute is to be subtracted. If the longitude is between 135° E, and 180°, two minutes are to be added, but subtracted if the given longitude is between 135° W, and 180°. This table is useful to find the time when the altitude of the pole star ought to be observed, to find the latitude by its meridian altitude; it is also useful in finding the variation of the compass by the pole star. Jan. Feb. Marc April. | May. June. July. Aug. Sept. 16h 93h562h 4' 43 52 2 O 26 36 34857 45 55 3 44 153 145 12 3 I I 54 4 16 11 23 9 33 7 25 [ 12 11 19 5 11 12 925 7 16 9 20 17 9 167 204 46 2 42 10 9 8 Difference of Altitude of the Pole Star and the Pole, at different distances of the Star from the Meridian. As the pole star is generally known, that no opportunity, therefore, may be lost for determining the latitude, this table is inserted, the use of which is as follows : Find the interval between the time of observation of the altitude of the pole star, and that of its passing the meridian, and take out the corresponding equation from the table; which added to, or subtracted from the true altitude of the pole star, will give the latitude of the place of observation. EXAMPLES. I. Let the corrected altitude of the pole star be 46° 10' N, observed 8h. 30' before its passage over the meridian. quired the latitude? True altitude of the pole star Latitude Re II At 1h. 10' after the passage of the pole star over the meridian, its altitude corrected was 58° 51' N. Required the latitude? Argument. Distance of the Star from the Meridian, in Sidereal Time 11 Hours 10 Hours.19 Hours. 8 Hours 7 Hours. 6 Hours. Min. ADD. Day's Sun's Declination for the Years 1808, 1812, 1816, 1820. Jan. Feb. Mar. April May June July Aug. Sept Oct. Nov. Dec. 223 017 37 84 5915 25 22 4 22 49 16 286 22 5 45 16 22 43 16 105 59 21 20 510 22 19 52 10 231 19 38 10 510 1811 2419 24 9 461 25 19 10 9 241 290 42 12 5213 16 13 4 131 54 20 13 23 28 20 29 12 14 20 25 23 27 20 17/11 34 20 36 23 27 20 511 5420 48 23 26 19 5311 14 20 58 23 25 19 40 10 26 18 559 12 923 23 19 27 10 27 18 40 8 392 3913 5221 1923-21 19 13/10 28 18 25 8 163 314 1121 29 18 97 54 3 26 14 30 21 30 17 53 3 4914 48 21 3117 36 24 1 17 12 3021 31 40 12 50:21 1123 20 42 2 413 11 21 21 23 17 212 27 13 31 21 3223 14 48 23 11 18 31 8 59 2 50 13 50 21 4223 10 21 561 18 16 8 381 14 10 123 EXPLANATION AND USE OF THIS TABLE. The Declination of the Sun is an arch of a meridian contained. between its centre and the equinoctial, which arch is reckoned in degrees, minutes, &c. In the first quadrant of the ecliptic, from about the 21st of March, to the 21st of June, the Sun's declination is North, and increasing and in the third quadrant, between the 22d of September and 21st of December, the Sun's declination is South, and increasing In the second quadrant of the ecliptic, from about the 21st of June to the 22d of September, the Sun's declination is North, and decreasing; and in the fourth quadrant, between the 21st of December and the 21st of March, the Sun's declination is South, and decreasing; which will be readily perceived by inspecting the table. In this table, the Sun's declination is given, from the year 1808 to 1823 inclusive, calculated for the instant of noon, cach day, at Days. Sun's Declination for the Years 1809, 1813, 1817, 1821. Jan. Feb. Mar April May. June. July. Aug. Sept Nov. Dec. S. N. N. N. N. N. N. S. S. ა. 1121 50 14 12 21 40 13 1321 30 13 1421 20 13 1521 912 422 11 9 43 18 16 20 58 12 221 47 10 5119 4 23 22 21 25 13 492 43 1720 46 12 11 23 10 26 19 18 23 24 21 16 13 302 20 18 20 34 11 400 59 10 47 19 31 23 25 21 513 11 57 19 20 22 11 180 36 11 819 44 23 27 20 55 12 51 33 22 18 36 23 16 21 44 14 27 3 29 8 618 13 23 14 20 20 S. 910 570 1211 28 19 57 23 27 20 44 12 32 1 10 10 18 19 41 23 27 21 19 56 10 350 1211 49 20 10 23 28 20 32 12 12 0 47 10 40 19 55 23 28 22 19 42 10 130 35 12 920 22 23 2820 2111 520 2311 120 08 23 28 N. S. 56 23 23 19 28 9 520 59 12 29120 33 23 24 19 14 9 29 1 23 12 49120 45 23 2518 59 9 71 46 13 9 20 26 18 44 8 452 10 13 28 21 10 12 2520 57 23 23 27 18 29 8 222 33 13 47 21 34 12 45 21 28 18 13 8 02 5714 621 27 23 19,19 39 48 157 13 521 3 2014 25 21 36 23 16 18 49 9 27 2 21 13 25 21 3 43 14 44 21 45 23 13 18 35 9 52 4413 45 21 21 54 18 211 8 411 14 5 the Meridian of Greenwich, or the meridian, at which we begin to reckon the Longitude. It is to be taken out with the month at the top, and the day in the left hand column, at the same time, noting whether it be North, or South, as expressed at the top of each column. The declination being here given to the nearest minute, it will be found sufficiently exact for the most common and useful problems, wherein it is concerned. The sun's declination is necessary to find the latitude, whether at sea or land, 'from the meridian altitude observed; it is also requisite for finding the latitude from two altitudes observed with the interval of time measured by a watch; it serves for comput ing the sun's azimuth, having his altitude and the latitude of the place given, in order to find the variation of the compass; it is required, jointly with the latitude of the place and the sun's horary angle, to compute his altitude, if neglected to be observed at the time of taking the moon's distance from the sun for finding the longitude, being useful to facilitate the calculation of the effect Days. Sun's Declination for the Years 1810, 1814, 1818, 1822. Jan. Feb. [Mar. April May. June. July. Aug. Sept Oct Nov. Dec 2 10 22 14 622 33 15 43 5 48 6 19 16 26 22 37 22 46 16 516 37 346 14 00 22 19 15 43 5 7 8 11.17 47 23 12 21 42 13 48 3 27 8 33 18 223 7 15 17 37 23 51 7 38:17 53 23 91 14 21 22 13 82 40 9 16 18 32 23 1621 46 14 313 35 018 923 13 21 19 59 10 410 11 44 20 6 23 28 20 35 12 4 20 19 23 24 20 30 23 44 20 42 23 28 20 23 11 18 13 352 26 9 718 55:23 22 8,13 16 2 29 29:19 10.23 24 26,20 57 12 561 39 9 5119 24 23 26 27 20 46 12 371 1610 13:19 38,23 27 N. S. 170 5210 3419 51 23 27 570 29 10 56 20 5 23 28 17 20 18 23 27 38 20 30 23 27 59 20 4223 25 423 24 19 34 10 351 512 20 20 54:23 24 14 23 28 12 40 21 5:23 22 29 18 1 3 14 14 21 21 34 23 43 23 13 18 39 9 10 2 38.13 40 21 37 23 12 14 21 521 of refraction and parallax upon the distance; it is also necessary to calculate the apparent time from an obsered altitude of the sun at a distance from the meridian, the latitude being given; or to compute the time of the sun's setting or rising; which, though a less accurate method than the former of obtaining the time, may yet be useful when that cannot be had. For any of these purposes the sun's declination must be found to the time given nearly, reduced to the meridian of Greenwich, making proportion according to its daily increase, or decrease, by the help of table 14, as in the following examples. 1st Required the Sun's Declination at noon in New-York, in Longitude 74° 8' West, on the 1st of April, 1811. Dec. for April 1st, 1811, at Greenwich, in Tab. 13 = 4° 18′ N. = +450" Required Declination 4° 22′ 50′′.N. |