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THOMPSON'S COAST' PILOT. 127 RvuLE.--If the distance at which a light of a given height can be seen by a person on a given level be required, it is only needful to add tegether the two numbers in the column of distances corresponding to those in the col- umn of heights, which represent respectively the height of the observer's eye and the height of the focal plane above the sea. When the height required to render a light visible at a given distance is required, we must -- first seek for the number corresponding to the height of the observer's eye, and deduct this from the whole proposed range of the light, and opposite the remuinder in the column of distances, seek for the corresponding num- ber in the column of heights. A tower, 100 feet high, will be visible to an observer, whose eye is elevated 15 feet above the water, 16 nautical miles, thus from the table: EXAMPLE.--15 feet elevation, distance visible, 4.443 nautical miles. 100 " i F ©: cd dA: di 15.918 . - TABLE OF THE ANGLES WHICH EVERY POINT AND QUARTER POINT OF THE hae MAKES WITH THE MERIDIAN. ai 9 Et " rae 7 ee 7 Nm ef " 2 48 45 | 24; 25 18 45 | 44 | 47 48 45 | 64) 70 18 45 37 380 | 24 | 28 07 380/44 | 50 387 30] 64) 73 O07 380 8 26 15 | 22; 380 56 15 | 48 | 538 26 15) 6% | 7 56 15 ps neh cr 12114. 08 45 |.32 186 38 45] 52 159 08 45 | 74] 81 88. 45 14116 52 30.| 34| 89.22 30154 | 61 52 30| 74 | 84 22 30 12/19 41 15 | 82/42 11 15 | 5% | 64 41 16 | 72] 87 11 15° THE LAKE COASTING TRADE. _. The bill for the regulation of the lake coasting trade, recently passed in the Senate, provides that the master of every vessel enrolled or licensed to engage in foreign and coasting trade on the northern, northeastern and northwestern frontiers of the United States, shall, before the departure of his vessel from a port in one collection district to a port in another collection district, present to the collector duplicate manifests, and obtain