PortCities London

Captain James Cook


Cook the navigator

Map of New Zealand
View full size image Map of New Zealand, 1772.
The other important science that advanced because of Cook's voyages was navigation. Cook was told to chart the places he visited as accurately as possible, and to 'lay down' (chart the outlines of) any unknown coasts that he sailed along.

This map shows the outline of New Zealand as charted by Cook in 1770. Superimposed on it, in red, is the actual outline of the two islands taken from a 20th-century Admiralty chart.

Cook completed the survey in only six months. Although the shape of the two islands is extremely accurate, they are actually about 32 km (20 miles) too far to the east. This is because it was still difficult to determine longitude precisely.

Where am I?

Royal Observatory
View full size imageThe Royal Observatory at Greenwich. © NMM
One of the problems with long-distance voyages of exploration was that it was extremely difficult to fix one's position at sea with any great accuracy.

Latitude – the imaginary lines that run horizontally around the world – was easy enough to determine, but longitude, the lines running vertically, was not.

On Cook's first voyage he took a book of lunar tables produced by the Royal Observatory in Greenwich. This helped him to find his longitude by measuring astronomical angles.

'My trusty friend the watch'

Cook's Chronometer, K1, the first copy of H4, by Larcum Kendall of London, 1769.
View full size image Cook's Chronometer, K1, the first copy of H4, by Larcum Kendall of London, 1769. © NMM
On Cook's second and third voyages his navigation was vastly improved when he took chronometers to help him find his longitude. The first working chronometer had just been invented by John Harrison. A condition of winning the prize of £20,000 for an accurate and reliable marine chronometer was that it could be made easily by other clock makers. 

Cook took one made by Larcum Kendall known as K1. He called it 'my trusty friend the watch'. Cook's success with K1 was instrumental in making the time method of finding longitude popular and following his voyages it was adopted on many naval expeditions.

Although chronometers were a faster and more accurate way of determining longitude, they were expensive, so lunar tables continued to be produced by the Royal Observatory for mariners until the early 20th century.

Centre for instrument making

The 'little midshipman': trade symbol of a Wapping instrument manufacturer.
View full size imageThe little midshipman, symbol of an instrument maker.
London was the largest producer of high-quality scientific instruments in the world in the mid-18th century. Cook's voyages were equipped with the latest scientific equipment from the top London manufacturers. As someone said at the time of Cook's ships: 'no people ever went to sea better fitted out for the purpose of natural history, nor more elegantly'.

This carved figure of a midshipman holding an octant stood outside William Heather's shop at 157 Leadenhall Street in the City of London. An octant was used for measuring the height of heavenly bodies above the horizon, in order to find latitude accurately. 


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