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A plan of Louisbourg - Public domain vintage map
Summary
Scale ca. 1:4,000 and ca. 1:10,000.
Manuscript, pen-and-ink and watercolor.
Depths shown by soundings.
Oriented with north to the left.
Has watermark.
LC Maps of North America, 1750-1789, 336
Available also through the Library of Congress Web site as a raster image.
Vault
AACR2: 651/1; 650/2; 650/3; 651/4
In the 17th century, maps took a huge leap forward. Mathematical and astronomical knowledge necessary to make accurate measurements had evolved. English mathematicians had perfected triangulation: navigation and surveying by right-angled triangles. Triangulation allowed navigators to set accurate courses and produced accurate land surveys. Seamen learned to correct their compasses for declination and had determined the existence of annual compass variation. Latitude determination was greatly improved with the John Davis quadrant. The measurement of distance sailed at sea was improved by another English invention, the common log. Longitudinal distance between Europe and Québec was determined by solar and lunar eclipses by the Jesuit Bressani in the 1640s and by Jean Deshayes in 1686. With accurate surveys in Europe, the grid of the modern map began to take shape.
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