Maps and survey . uished by some special sign, for theyare important from the fact that it is easy to breach their banksand flood the surrounding country. The characteristic sheet of the French 1/50,000 map distin-guishes between important rivers, shown double ; streams, shownby single lines ; and canalised rivers, margined by thick bluelines, with signs for locks. Bridges of stone, steel, and wood ;suspension and swing bridges; ferries, and wiers, are all givenconventional signs. The International Map has a quite different set of signs,suitable to its smaller scale. Perennial rivers are shown
Maps and survey . uished by some special sign, for theyare important from the fact that it is easy to breach their banksand flood the surrounding country. The characteristic sheet of the French 1/50,000 map distin-guishes between important rivers, shown double ; streams, shownby single lines ; and canalised rivers, margined by thick bluelines, with signs for locks. Bridges of stone, steel, and wood ;suspension and swing bridges; ferries, and wiers, are all givenconventional signs. The International Map has a quite different set of signs,suitable to its smaller scale. Perennial rivers are shown bya solid blue line of varying width; non-perennial are heavilylong-dotted. Unsurveyed rivers are lightly dotted; and navi-gable rivers are shown by a double line. Navigable canals havecross strokes similar to those often used for railways, and non-navigable are distinguished from natural streams by theiruniformity. There are signs for rapids and falls, and for thelimit of navigation. PLATE III CONVENTIONAL SIGNS. y f
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectsurveying, bookyear19
