+-------+--------+--------++-------+--------+--------+ | | λ | λ′ || | λ | λ′ | | H | Lengths|Lengths || H | Lengths|Lengths | |Heights| in | in ||Heights| in | in | | in |English |Nautical|| in |English |Nautical| | Feet. | Miles. | Miles. || Feet. | Miles. | Miles. | +-------+--------+--------++-------+--------+--------+ | 5 | 2·958 | 2·565 || 110 | 13·874 | 12·03 | | 10 | 4·184 | 3·628 || 120 | 14·490 | 12·56 | | 15 | 5·123 | 4·443 || 130 | 15·083 | 13·08 | | 20 | 5·916 | 5·130 || 140 | 15·652 | 13·57 | | 25 | 6·614 | 5·736 || 150 | 17·201 | 14·91 | | 30 | 7·245 | 6·283 || 200 | 18·708 | 16·22 | | 35 | 7·826 | 6·787 || 250 | 20·916 | 18·14 | | 40 | 8·366 | 7·255 || 300 | 22·912 | 19·87 | | 45 | 8·874 | 7·696 || 350 | 24·748 | 21·46 | | 50 | 9·354 | 8·112 || 400 | 26·457 | 22·94 | | 55 | 9·811 | 8·509 || 450 | 28·062 | 24·33 | | 60 | 10·246 | 8·886 || 500 | 29·580 | 25·65 | | 65 | 10·665 | 9·249 || 550 | 31·024 | 26·90 | | 70 | 11·067 | 9·598 || 600 | 32·403 | 28·10 | | 75 | 11·456 | 9·935 || 650 | 33·726 | 29·25 | | 80 | 11·832 | 10·26 || 700 | 35·000 | 30·28 | | 85 | 12·196 | 10·57 || 800 | 37·416 | 32·45 | | 90 | 12·549 | 10·88 || 900 | 39·836 | 34·54 | | 95 | 12·893 | 11·18 || 1000 | 41·833 | 36·28 | | 100 | 13·228 | 11·47 || | | | +-------+--------+--------++-------+--------+--------+ If the distance at which a light of given height can be seen by a person on a given level be required, it is only needful to add together the two numbers in the column of lengths λ or λ′ (according as Nautical or English miles may be sought) corresponding to those in the column of heights H, which represent respectively the height of the observer’s eye and the height of the lantern above the sea. When the height required to render a light visible at a given distance is required, we must seek first for the number in λ or λ′ corresponding to the height of the observer’s eye, and deduct this from the whole proposed range of the light, and opposite the remainder in λ or λ′ seek for the corresponding number in H. ~Diagonal Lantern.~