EXPLANATION OF THE TABLES. Table I contains the parts of Mercator's meridian, to every other minute. The parts for any odd minute may be found with sufficient exactness, by taking the arithmetical mean between the next greater and the next less. For the uses of this table, see Navigation, Sec. III. Table II gives the depression or dip of the horizon at sea for different heights. Thus if the eye of the observer is 20 feet above the level of the ocean, the angle of depression is 4' 24". See Art. 99. This table is calculated according to the rule in Note I, which gives the depression 59" for one. foot in altitude; allowance being made for the mean terrestrial refraction. In Table III is contained the depression for different heights and different distances, when the view of the ocean is more or less obstructed by land. Thus if the height of the eye is 30 feet, and the distance of the land 24 miles, the depression is 8'. See Note I. Table IV contains the curvature of the earth, or the difference between the true and the apparent level, for different distances, according to the rule in Art. 161. Thus for a distance of 17 English miles, the curvature is 192 feet. Table V contains the distances at which objects of different heights may be seen from the surface of the ocean, in the mean state of the atmosphere. This is calculated by first finding the distance at which a given object might be seen, if there were no refraction, and then increasing this distance in the ratio of √7 : √6. See Note A. Table VI contains the polar distance and the right ascension in time, of the pole star, from 1800 to 1820. From this it will be seen, that the right ascension is increasing at the rate of about 14 seconds a year, and that the north polar distance is decreasing at the rate of 19 seconds a year. From the latitude of the place, and the polar distance of the star, its azimuth may be calculated, when it is at its greatest distance from the meridian. The time when it passes the meridian may be ascertained by finding the difference between the right ascension of the star and that of the sun. Note L. See 로 TABLE I. MERIDIONAL PARTS. M. 0° 1° 2° 3° 4° 5° 6° 7° 8° 9° 10° 11° 12° M. 2 2 4 4 6 6 8 8 0 0 60 120 180 240 300 361 421 482 542 603 664 725 0 62122 182 242 302 363 423 484 544 605 666 727 2 64 124 184 244 304 365 425 486 546 607 668 729 66 126 186 246 306 367 427 488 548 609 670731 6 68 128 188 248 308 369 429 490 550 611 672734 10 10 12 12 14 14 16 16 18 18 20 20 22 22 70 130 190 250 310 371 431 492 552 613 674 736 10 72 132 192 252 312373 433 494 554 615 676 738 12 74 134 194 254 314 375 435 496 556 617 678740 14 76136 196 256 316 377 437 498 558 619 680 742 16 78 138 198 258 318 379 439 500 560 621 682 744 18 80 140 200 260 320 381 441 502 562 623 684 746 20 82142 202 262 322 353 443 504 565 625 687 748 22 24 24 84 144 204 264 324 385 445 506 567 627 689 750 24 26 26 86 146 206 266 326 387 447 508 569 629 691752 26 28 28 88 148 208 268 328 389 449 510 571 632 693 754 28 30 30 90 150210270331391 451 512 573 634 695 756 30 32 32 92152212272 333 393 453 514 575 636 697 758 32 34 34 94154 214 274 335 395 455 516 577 638 699 760 34 36 36 96 156 216 276 337 397 457 518 579 640 701 762 36 38 38 98158 218 278 339 399 459 520 581 642 703 764 38 40 40 100 160 220 280 341 401 461 522 583 644 705 766 40 42 42 102 162 222 282 343 403 463 524 585 646 707 768 42 44 44 104 164 224 284 345 405 465 526 587 648 709 770 44 46 46 106 166 226 286 347 407 467 528 589 650 711 772 46 48 48 108 168 228 288 349 409 469 530 591 652713774 48 50 50 110 170 230 290 351 411 471 532 593 654 715777 50 52 52 112 172 232 292 353 413 473 534 595 656 717 779 52 54 54 114 174 234 294 355 415 476 536 597 658 719 781 54 56 56 116 176 236 296 357 417 478 538 599 660 721783 56 58 58 118 178 238 288 359 419 470 540 601 662 723 785 58 M. 0° 1° 2° 3° 4° 5° 6° 70 80 90 100 110 120 M. TABLE I. MERIDIONAL PARTS. M. 13° 14° | 15° | 16° | 17° | 18° | 19° | 20° | 21° | 22° |M. 0 787 848 910 2 789 851 913 4 791 853 915 6 793 855 917 8 795 857 919 10 797 859 921 12 799 861 923 14 801 863 925 16 803 865 927 18 805 867 929 973 1035 1098 1161 1225 1289 1354 0 975 1037 1100 1164 1227 1291 1356 2 977 1039 1102 1166 1229 1293 1358 979 1042 1105 1168 1232 1296 1360 6 981 1044 1107 1170 1234 1298 1362 8 983 1046 1109 1172 1236 1300 1364 10 985 1048 1111 11741238 1302 1367 12 987 1050 1113 1176 1240 1304 1369 14 989 1052 1115 1178 1242 1306 1371 16 991 1054 1117 1181 1245 1308 1373 18 20 807 869 931 994 1056 1119 1183 1246 1311 1375 20 22 809 871 933 996 1058 1121 1185 1249 1313 1377 22 24 811 873 935 998 1060 1123 1187 1251 1315 1380 24 26 813 875 937 1000 1063 1126 1189 1253 1317 1382 26 28 816 877 939 1002 1065 1128 1191 1255 1319 1384 28 30 818 879 942 1004 1067 1130 1193 1257 1321 1386 30 32 820 882 944 1006 1069 1132 1195 1259 1324 1388 32 34 822 884 946 1008 1071 1134 11981261 1326 1390 34 36 824 886 948 1010 1073 1136 1200 1264 1328 1393 36 38 826 888 950 1012 1075 1138 1202 1266 1330 1395 38 40 828 890 952 1014 1077 1140 1204 1268 13321397 40 42 830 892 954 1016 1079 1142 1206 1270 1334 1399 42 44 832 894 956 1019 1081 1145 1208 1272 1336 1401 44 46 834 896 958 1021 1084 11471210 1274 13391403 46 48 836 898 960 1023 1086 1149 1212 1276 1341 1406 48 50 838 900 962 1025 1088 1151 1215 1278 1343 1408 50 52 840 902 964 1027 1090 1153 12171281 1345 1410 52 54 842 904 966 1029 1092 1155 1219 12831347 1412 54 56 844 906 969 1031 1094 1157 1221 1285 1349 1414 56 58 846 908 971 1033 1096 1159 1223 1287 1352 1416 58 M. 13° 14° 15° 160 170 180 190 200 210 22° M. |