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Sea watch

The whole story of exploration: part one, brave new world

Image credit: Getty Images, Diomedia

Map-making goes back to the dawn of exploration, but the first systematic approaches only became possible with the arrival of time-keeping technology.

Although humankind’s migration out of the African continent started some two million years ago, this gradual spread through tribal relocation across the globe isn’t exploration in modern terms. We tend now to think of the purpose of exploration in economic, geopolitical and resource availability terms. The way we have sought to make that easier, notes Eugene Rae, expert in the history of exploration instrumentation and artefacts at Royal Geographical Society, “is to have better technology”.

It was three millennia ago that the Phoenicians set out on their maritime explorations, navigating by the stars. A little over two millennia ago, Pythias the Greek ‘discovered’ what is now Britain by sailing past Gibraltar out of the Mediterranean Sea and heading north. Yet these ancient and apparently ad hoc forays into the unknown have little to do with technological breakthrough, and more to do with a hunger for gold.

Likewise, although Zhang Qian’s travels into China’s interior in the first century BCE have the appearance of exploration, his real motivation was to raise an army for the Emperor. Early travellers along the Silk Route penetrated deep into central Asia, while early Christian missionaries travelled east across Europe as far as modern Russia and Turkey. Ptolemy pioneered early cartography, but most early map-makers often got it badly wrong, their efforts being of limited navigational value.

It was with Ibn Battuta in the early 14th century that the dawn of modern exploration came. While there’s nothing particularly important about his journey from Morocco to Mecca along a fairly well-established route, the difference was that he spent 24 years doing it. He recorded his adventures in a work entitled ‘A Gift to Those Who Contemplate the Wonders of Cities and the Marvels of Traveling’.

The following century saw the start in earnest of systematic, state-sponsored exploration, in the form of Prince Henry the Navigator’s efforts to plant the Portuguese flag. Henry’s voyages were to colonise islands such as the Azores and the Canaries, which became vital jumping-off and resupply points for maritime explorers en-route to the Americas, India and the Far East. With morality as its fossil fuel, this approach to exploration led to the slave trade, and brought massive economic growth to Europe through commerce in silver, silk, textiles, spices and indigo. Ultimately, it was the dawn of international, trans-oceanic economy that led the way for exploration in the quest for resources and wealth.

For Rae, it is the Renaissance that really started the technological surge. “We’re talking about the Portuguese and the Spanish with their use of instruments such as the astrolabe, a device used for navigating by the stars.” The astrolabe, an inclinometer that could calculate a ship’s latitude providing the local time was known, had existed since ancient times. Yet, during the time of Henry the Navigator, they were redesigned and stabilised specifically for marine use, first made of metal and batch produced. By the mid-16th century a related instrument, the ‘nocturnal’, was used to calculate latitude – as its name hints – at night from the relative position of two known stars.

“This was just the start,” says Rae, noting that it was around this time the portable quadrant (essentially a quarter of an astrolabe) became popular in maritime exploration. By the end of the 16th century, navigator John Davis had invented the ‘backstaff’, which measured the Sun’s position from a projected shadow (similar in concept to the sun-dial that dates back to ancient Egyptian astronomy).

The big drawback to these instruments (apart from their inaccuracy) was they damaged the users’ eyes. “The later sextant was not only more accurate, but was safer to use,” says Rae.

“Quadrants were the navigational instruments that would have been used in most voyages up to Captain Cook,” Rae adds, yet Cook is significantly different: “his three late-18th-century voyages were for scientific investigation.”

In navigational terms, the leap forward was the appearance of ships’ chronometers that would give the explorer a precise calculation of longitude, which meant that true position at sea was starting to take shape. Cook used the K1 (a copy of John Harrison’s famous ground-breaking H4). Yet the problem was cost. During Cook’s time, the outlay represented 30 per cent of the ship’s value. But by the 19th century, the cost had fallen to the equivalent of two-weeks’ wages.

Sea watch

Harrison’s longitude revolution

When it comes to calculating a precise position at sea, the mariner needs to know latitude and longitude: the intersection of the two represents an exact location. While the former is relatively easy to calculate with an inclinometer fixed on a celestial body (such as the Sun) at a known time (such as noon), calculating precise longitude is much more complex, as it relies on accurately knowing time, and the time back at your home port. Until the 18th century, this could not be achieved because pendulum clock technology cannot be relied on at sea.

In 1714, the British government offered a prize of £20,000 (£3m in today’s money) to the person that could provide a ‘Practicable and Useful’ solution to determining longitude at sea. This is where the Yorkshire horologist and engineer John Harrison comes into the picture. Harrison came up with the H4 ‘sea watch’ – a 5.2in diameter circular instrument resembling a modern watch – that was first trialed in 1761. By the turn of the century, the H4 (and its numerous clones) had become a routine fixture on long voyages and the problem of longitude was solved.

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