The (Edited from Wikipedia)

SUMMARY

The octant, also called reflecting quadrant, is a used primarily in navigation. It is a type of . The name octant derives from the Latin octans meaning eighth part of a circle, because the instrument's arc is one eighth of a circle.

Reflecting quadrant derives from the instrument using to reflect the path of light to the observer and, in doing so, doubles the angle measured. This allows the instrument to use a one-eighth of a turn (45 degrees) to measure a quarter-turn or quadrant (90 degrees).

HISTORY

Two men independently developed the octant around 1730: (1682–1744), an English mathematician, and Thomas Godfrey (1704–1749), a glazier in Philadelphia. While both have a legitimate and equal claim to the invention, Hadley generally gets the greater share of the credit. This reflects the central role that and the Royal Society played in the history of scientific instruments in the eighteenth century.

THE NAVAL DISASTER OF SCILLY

The Scilly naval disaster of 1707 was the loss of four warships of a fleet off the in severe weather on 22 October 1707. 1550 sailors aboard the wrecked vessels lost their lives, making the incident one of the worst maritime disasters in the history of the British Isles. The main cause of the disaster was the navigators' inability to accurately calculate their positions.

In the summer of 1707, during the War of the Spanish Succession, a combined British, Austrian and Dutch force under the command of besieged and attempted to take the French port of Toulon.

During this campaign, which was fought from 29 July to 21 August, Great Britain dispatched a fleet to provide naval support. Led by the Commander-in-Chief of the

1 British Fleets, Sir Cloudesley Shovell, the ships sailed to the Mediterranean, attacked Toulon and also managed to inflict damage on the French fleet caught in the siege. The overall campaign was nevertheless unsuccessful and the alliance was ultimately defeated by Franco-Spanish units. The British fleet was ordered to return home, and set sail from Gibraltar to Portsmouth in late September. The force under Shovell's command comprised fifteen ships.

Shovell's fleet of twenty-one ships left Gibraltar on 29 September. The passage was marked by extremely bad weather and constant squalls and gales. As the fleet sailed out on the Atlantic, passing the Bay of Biscay on their way to , the weather worsened and storms gradually pushed the ships off their planned course. Finally, on the night of 2 November 1707, the squadron entered the mouth of the English Channel and Shovell's sailing masters believed that they were on the last leg of their journey.

The fleet was thought to be sailing safely west of Ushant, an island outpost off the coast of Brittany. However, because of a combination of the bad weather and the mariners' inability to accurately calculate their , the fleet was off course and closing in on the Isles of Scilly instead. Before their mistake could be corrected, the fleet struck rocks and four ships were lost.

The exact number of officers, sailors and marines who were killed in the sinking of the four ships is unknown. Statements vary between 1,400 and over 2,000, making it one of the greatest maritime disasters in British history. For days afterwards, bodies continued to wash onto the shores of the isles along with the wreckage of the warships and personal effects. Many dead sailors from the wrecks were buried on the island of St Agnes. Shovell's body, along with those of his two Narborough stepsons and his flag-captain, Edmund Loades, washed up on Porthellick Cove on St Mary's the following day, almost seven miles (11 km) from where the Association was wrecked.

The disastrous wrecking of a Royal Navy fleet in home waters brought great consternation to the nation. The main cause of the catastrophe has often been portrayed as the navigators' inability to accurately calculate their longitude. Clearly, something better than dead reckoning was needed to find the way in dangerous waters. As transoceanic travel grew in significance, so did the importance of reliable navigation. This eventually led to the in 1714, which established the and offered large financial rewards for anyone who could find a method of determining longitude accurately at sea. After many years, the consequence of the Act was that accurate marine chronometers were produced and the lunar distance method was developed, both of which became used throughout the world for navigation at sea.

2 THE LONGITUDE ACT

The Longitude Act was an Act of Parliament of the United Kingdom passed in July 1714 at the end of the reign of Queen Anne. It established the Board of Longitude and offered monetary rewards (Longitude rewards) for anyone who could find a simple and practical method for the precise determination of a ship's longitude. The Act of 1714 was followed by a series of other Longitude Acts that revised or replaced the original.

As transoceanic travel grew in significance, so did the importance of accurate and reliable navigation at sea. Scientists and navigators had been working on the problem of measuring longitude for a long time. While determining latitude was relatively easy, early ocean navigators had to rely on dead reckoning to find longitude.

This was particularly inaccurate on long voyages without sight of land and could sometimes lead to tragedy, as during the Scilly naval disaster of 1707 which claimed the lives of nearly 2,000 sailors. This brought the problem of measuring longitude at sea into sharp focus once more. Following the Merchants and Seamen Petition, which called for finding an adequate solution and was presented to Westminster Palace in May 1714, the Longitude Act was passed in July 1714.

The Longitude Act offered a series of rewards, rather than a single prize. The rewards increased with the accuracy achieved: £10,000 for anyone who could find a practical way of determining longitude at sea to an accuracy of not greater than one degree of longitude (equates to 60 nautical miles (110 km; 69 mi) at the equator).

[NOTE: One British pound (£) in 1750 would be equal to 200 pounds in 2015 due to the effects of central bank inflation over that time period. In 2016, one British pound is equivalent to about $1.25 US dollars. So 10,000 British pounds from the early would be equivalent to about $2.5 million US dollars.]

The reward was to be increased to £15,000 if the accuracy was not greater than 40 minutes, and further enhanced to £20,000 if the accuracy was not greater than half a degree. Other rewards were on offer for those who presented methods that worked within 80 geographical miles of the coast (being the most treacherous part of voyages) and for those with promising ideas who needed help to bring them to readiness for trial.

Many rewards were paid out over the 114 years of the Board of Longitude's existence. John Harrison received more money than any other individual, with several rewards from the -1750s, and £10,000 in 1765.

3 Subsequent Longitude Acts offered different rewards. That of 1767 held out £5,000 for improvements to Tobias Mayer's lunar tables and that of 1774 halved the amount offered for any method or instrument achieving the degrees of precision outlined in the original Act (i.e. £5,000 for a degree, £7500 for 2/3 of a degree or £10,000 for 1/2 degree).

The 1818 Longitude Act, which completely revised the composition and remit of the Board of Longitude, again changed the rewards, by now offered for improvements to navigation in general rather than simply for finding longitude. In addition, the Act outlined rewards for navigating the North West Passage, again on a sliding scale from £20,000 for reaching the Pacific through a north west passage to £5,000 for reaching 110 degrees west or 89 degrees north and £1000 for reaching 83 degrees north. In 1820 £5,000 was paid to the officers and crews of HMS Hecla (1815) and HMS Griper (1813) under this Act.

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