 |
|
|
History of Navigation:
Navigation in the 19th to 20th Centuries |
Foundations for advancing navigation had been laid by 1800; more developments made these advances practical for mariners like most of Maine’s sailing ship captains who went to sea in the nineteenth century.
Deep sea navigators benefited as charts, publications and instruments became available and affordable to the average captain. Surveys and sailing directions became more accurate, and oceanographic and weather data was collected and put into an accessible form. Those sailing to familiar ports on a regular basis or those fishing off the coast of Maine had learned most of the needed landmarks, compass courses, and depths, but they also benefited from accurate charts and government-installed aids to navigation.
|
Dead Reckoning Tools
Mechanical logs, first invented around the middle of the 17th century, became practical and reliable around the mid-1800s. These mechanical logs measured distance traveled, like an odometer. An impeller was turned by water flow; a mechanical counter recorded these impeller turns, converting them to nautical miles. Some logs, including [Walker's Harpoon log] of the 1860s, had the dials on the same part that had the impeller. The log had to be recovered and released for every log entry. Taffrail logs, where the impeller turned a stiff rope attached to a geared readout mounted on the taffrail of the ship, did not have to be hauled. The patent logs of the 19th century improved the quality of dead reckoning entries, thus improving navigation both at sea and along coasts.
|
|
Taking advantage of the same concepts of the patent logs, but far less common were mechanical depth sounders. One type used impellers to measure depth by counting the rotations the impeller made as it was dropped. Another type measured depth using seawater pressure. It used a glass tube, open on one end. As the air-filled tube was dropped the increasing water pressure pushed an indicator, compressing the air, further into the tube. When raised the indicator did not move out and the depth was read.
|
|
Publications for the Mariner
After the Napoleonic Wars and the War of 1812, major nations sent a flurry of exploring expeditions around the world. These expeditions brought back data on weather, oceanography, and coasts. They formed the foundation for much of the information that navigators continue to use.
Commercial publishers had been producing charts and sailing directions since the early 19th century. But it was not until the mid 19th century that chart publication became largely governmental and even then, commercial publishers continued to print charts.
In Britain, the Admiralty began publishing its own charts. From 1829 to 1855, its famous hydrographer, Francis Beaufort, led the Hydrographic Office, and made the Admiralty chart the world-wide standard. Commercial publishers used Admiralty and other information to publish blueback charts for merchant ships, used by British and American captains alike.
The United States Coast Survey was formed in 1807 by Thomas Jefferson to chart American coasts. The Coast Survey’s founder Ferdinand R. Hassler was a careful surveyor, but it was not until his successor, Alexander Dallas Bache, that many charts were published for government and commercial use.
|
Bache, great-grandson of Benjamin Franklin, led the U.S. Coast Survey from 1843 to 1865.
In the late 1870s and 1880s the Coast Survey began to publish detailed charts of the Maine coast. Before then, captains learned the coast by eye and used less-detailed privately-published coastal charts.
Edmund M. Blunt, and later his two sons, Edmund and George W., published the two most important pre-Civil War American navigational texts: Nathaniel Bowditch’s 1802 The New American Practical Navigator and The American Coast Pilot (pictured above). The Practical Navigator included basic instruction on navigation and tables to help solve problems. Searsport’s captains honored Bowditch by naming a cemetery for him. Blunt’s The American Coast Pilot, published from 1796 to 1867 provided sailing directions for the East Coast. It was replaced by the U.S. Coast Survey’s sailing directions, first published in 1878. Much of this work was prepared by Lieutenant Matthew Fountaine Maury.
|
|
|
From the 1840s to 1860s Lieutenant Maury was responsible for collecting and publishing wind and current data, using information compiled from thousands of ship’s logs. In 1847 the Navy published a North Atlantic wind and current chart, followed by a more general publication of pilot charts showing winds and currents of all oceans. These, along with sailing directions, helped navigators select routes to take advantage of favorable winds and currents. Maury never received due credit because he joined the Confederate Navy during the Civil War.
The nineteenth century also saw developments in celestial navigation sight reductions that simplified calculation of position.
Instruments for Celestial Navigation
Production chronometers were the most important instrument for celestial navigation, but there was also steady improvement in altitude measuring instruments.
|
Sextants and octants were steadily reduced in size and had features added. Most were made in England. The octant or [Hadley’s quadrant] with its wooden frame went out of fashion and production by about 1850, superseded by the sextant which could be more easily used to measure lunar distances. Sextant makers focused on using metal frames to support the longer arc. These started to be made in quantity shortly into the 19th century and by mid-19th century these were the standard instrument.
|
|
|
Related Links and Downloads:
|
|
|
|
|
|
 |
