Posts Tagged ‘chronometer’


Wednesday, August 23rd, 2017

‘He [John Harrison] wrested the world’s whereabouts from the stars, and locked the secret in a pocket watch’. Dava Sobel, Longitude, Fourth Estate, 1998

Harrison H-4 Chronometer

Since earliest times sea-faring nations such as England, Portugal, France, Spain and the Netherlands vied with each other to solve – the Holy Grail of Navigation – longitude – calculating with precision a ship’s position while at sea beyond sight of land.

1714:  Legislation, The Act of Longitude 1714, followed an enquiry into England’s first recorded 18th century maritime disaster.

In 1707 in heavy weather off the Cornish coast six (6) of Admiral Shovell’s ships lost their bearings and dashed to pieces on the Scilly Isles with the loss of 1500 lives.

Under the 1714 Act a Board of Longitude was established to invite and evaluate submissions and award a prize of £20,000 to whom-so-ever solved the problem of longitude.



Tuesday, August 15th, 2017

‘The grim roll-call broke his [Cook’s) heart…the death of the astronomer Charles Green marked a wave of those who ‘departed this life’….By the end of January [1771] they had barely enough men to man the ship [HMS Endeavour]’. Vanesssa Collingridge, Captain Cook, The Life, Death and Legacy of History Greatest Explorer, Ebury Press, 2002

Charles Green son of ‘a prosperous’ free-hold Yorkshire farmer was born in Swinton towards the end of 1734. He received a broad education with a strong emphasis on science.

John his elder brother having taken Holy Orders established a school in Soho, London. Charles found his ‘heavenly passion’ astronomy. After he graduated Charles staying on for a time to assist John with the teaching of mathematics.

In 1760 Charles applied successfully for the position of Assistant Astronomer at Greenwich Observatory. He served three (3) Astronomer Royals in that capacity.

James Bradley first of these men had, in 1742, succeeded Edmond Halley of comet fame who held the post of Astronomer Royal for twenty-two (22) years from 1720-1742.

Bradley is celebrated principally for his work on the speed of light. In 1728 he estimated light moved at the speed of 295,000 km (183,000 miles) per second.

Three (3) centuries later – 2017 – Bradley’s calculations were amended to 299,790 km (186,290 miles) per second.

If only Bradley had stuck to light and left time and longitude to Mr. John Harrison inventor of the sea-going ‘pocket-watch’ – an accurate marine chronometer – many a sea-farer would not have met a watery end. Bradley’s tenure lasted twenty (20) years he died in 1762.



Tuesday, August 15th, 2017

Compared with that of Banks, Mr. Green’s equipment was comparatively modest. On May 5th, 1768, at a meeting of Council of the Royal Society it was resolved that the instruments for the use of the Observers of the South Latitudes be the following:

 Two [2] reflecting telescopes of two [2] foot focus…[1] brass Hadley’s sextant, [1] barometer bespoke of Mr Ramsden, [1] Journeyman’s Clock bespoke by Mr Skelton, two [2] Thermometers of Mr Bird, [1] Stand for Bird’s Quadrant, [1] dipping needle bespoke by Mr Ramsden’. H.C. Cameron, Sir Joseph Banks, Angus and Robertson, Sydney, 1966

Here two (2) of a plethora of questions must be asked. Who was Mr. Green and why did HMS Endeavour sail on such an important voyage without Mr. John Harrison’s H-4 chronometer?



Wednesday, August 9th, 2017

‘But by reason of the motion of the Ship, the Variation of Heat and Cold, Wet and Dry, and the Difference of Gravity in different Latitudes, such a watch hath not yet been made”. And not likely to be, either, he implied’.  Isaac Newton cited, Dava Sobel, Longitude, Fourth Estate, London, 1998

‘Not likely’ – not so – as early as 1736, on a timed voyage, England to Lisbon aboard HMS Centurian, H-1 a marine clock had shown itself a reliable time-keeper.

‘He [Harrison] succeeded, against all odds, in using the fourth – temporal – dimension to link points on the three-dimensional globe’. Sobel ibid.

Accurate time-keeping was essential to the calculation of longitude that gave a ship’s precise position at sea when beyond sight of land.

‘John Harrison, the man who solved longitude in 1759’. Peter Ackroyd, Revolution, Macmillan, 2016

Harrison was the carpenter from Yorkshire whose invention, the sea-going watch, solved the problem of longitude.