The classic example occurred on the night of 23rd October 1707, when the navigating officers of Admiral Sir Cloudesley Shovell's fleet, returning to England from Gibraltar in foul weather, thought themselves to be in open sea off Ushant. In fact, they were a hundred and twenty miles to the northwest, bearing down under full sail on the rocks of the Scilly Isles. Four ships were lost and two thousand men drowned in the disaster — the worst British shipwreck of all time.
Such dreadful mistakes were made because seamen could easily find latitude by measuring the angle over the horizon of the sun at noon. But longitude, the other half of the equation, and the key to precise navigation, could not be determined at sea by most mariners until almost the end of the eighteenth century. See Dava Sobel's superb book Longitude for the full and fascinating details, but, briefly, the solution involved either a chronometer (a highly accurate clock) and relatively simple calculations, or lunar observations and hideously complex calculations.
The lunar method came first, developed by Tobias Meyer, among others, and was tried at sea from 1757. It involved neither conceptual leaps nor special equipment, springing directly from routine astronomical theory. But it demanded books of special tables, plus formidable mathematical skill, and in practice was too complex for mariners to handle.
It's not beyond the realms of possibility that a mathematician like Van Oosterhout, backed by Utrecht University, might have anticipated Tobias Meyer by a few years… In any event, it makes a damn good story.
Van Oosterhout wasn't just a mathematician. He knew how to poke a man in the eye and kick him where it hurts. And he knew how to trip, duck, strike and chop. He was proficient in silat, a martial art practised for centuries in Indonesia — or Batavia, as it was known in his time, when it was a Dutch colony.
There's nothing special or unusual in Indonesia having its own brand of martial art, since it's hard to find any civilised Asian country that hasn't got one: jiu jitsu in Japan, taek-wondo in Korea, kung fu in China, and so on.
What all these arts have in common is that — unlike a loaded pistol, for example — they cannot instantly be picked up and used. Proficiency is bought at the high price of years of practice and muscular development… We must presume, therefore, that Cornelius Van Oosterhout put in the hours and kept himself fit.
Smallpox is horrible. The World Health Organisation estimates that the disease killed hundreds of millions of people in the twentieth century alone. In Europe, where the disease was endemic, it killed up to 30 per cent of affected adults and 80 per cent of children, and those it didn't kill it mutilated. Among the native populations of the Americas — lacking genetically acquired resistance — it was far worse.
In 1798, Edward Jenner demonstrated that vaccination — exposure to cow-pox virus — gave immunity to smallpox. But inoculation — exposure to weakened smallpox virus — was much older. The practice was established in Africa and Turkey from ancient times. In 1717 Lady Mary Wortley Montague described the Turkish technique — the very same that was applied to the young Joe Flint — but her efforts to popularise it in England were thwarted by strong medical opposition. During smallpox epidemics in eighteenth-century Boston, Benjamin Franklin noted that some slaves were immune to the disease, having been inoculated in their native lands; again the technique was ridiculed by the medical profession.1
Eventually the doctors learned, and smallpox vaccine was mass-produced and deployed worldwide. So all those who believe that Nature is good and Science is bad should contemplate the eradication of this vile disease: a triumph that stands beside Beethoven's symphonies, Gothic cathedrals and the US Constitution as a great and noble work of mankind.
In Chapter 13, Ben Gunn opens a fifty-year-old grave, releasing smallpox which infects the island's monkeys, who pass the disease to Silver's men. This story is based upon half-truth. It is fact that a thirty-year-old grave, accidentally opened in Somerset in 1759, released a foul stench, and many onlookers later contracted smallpox, though it was a weak form of the disease and all survived. But the idea of monkeys harbouring smallpox and then transmitting it to humans is entirely my invention.
On the other hand… transmission of diseases from animals to humans was once common. Such infections are termed zoonotic diseases. Tuberculosis, for instance, can pass from cows to humans, while other diseases originating in animals include plague and rabies. Finally, much debate has been generated within the scientific community over the possibility that the AIDS pandemic arose from a pre-existing illness in monkeys, and it is known that simian retroviruses can pass from monkeys to humans.
The smallpox virus is different, but it is a virus and my fiction is at least reasonable fiction.
So mind how you go when you meet a monkey.