On the 27th of January, 1854, two men lay stretched at the foot of an immense weeping willow, chatting, and at the same time watching most attentively the waters of the Orange River. This river, the Groote of the Dutch, and the Gariep of the Hottentots, may well vie with the other three great arteries of Africa—the Nile, the Niger, and the Zambesi. Like those, it has its periodical risings, its rapids and cataracts. Travellers whose names are known over part of its course, Thompson, Alexander, and Burchell, have each in their turn praised the clearness of its waters, and the beauty of its shores.
It is perhaps not surprising that Jules Verne has a novel about the metric system. As scientific correspondence became more common, it became clear to physicists and others that there was a need for a standard length measurement based on some common reference point. The two early suggestions for how to do this were to take some particular distance relative to the Equater and the Poles, or to use a pendulum set-up. The former eventually became the preferred option because it became clear that the pendular method was not giving sufficiently equivalent results (due to differences in gravity). So the French Academy of Sciences in 1790 defined the mètre as one ten-millionth the difference between the Equater and the North Pole. However, measuring a distance of this magnitude is an extraordinarily complicated undertaking, because it requires not just a measurement but an expedition of measurements -- and Verne, from his fascination with geography loves stories about scientific expeditions. It probably came to mind because in 1867 there was a big movement to regularize geodetic measurements across countries.
Not every nation, of course, joined the metric system bandwagon; the two major holdouts in Europe were England and Russia. And that gives us the background of the tale, The Adventures of Three Englishmen and Three Russians in South Africa (also called Meridiana or Measuring a Meridian; note that the English translations always put the Englishmen first despite the French putting the Russians first). The essential conceit of the work is that the English and the Russians are considering joining the meter club, but they are unwilling to do anything public without establishing their own measurements. So they send a joint expedition to South Africa to measure the 24th meridian east. Three Englishmen -- William Emery, Sir John Murray, and Colonel Everest -- meet up with three Russians -- Matthew Strux, Nicholas Palander, and Michael Zorn -- and together with a half-English, half-San guide, Makoum, they set out to make their measurements and calculations. They are in dangerous territory, however. There are wild beasts a-plenty, and hostile tribes, and, perhaps worst of all, in the middle of their expedition England and Russia go to war with each other (the Crimean War), thus splitting the two groups. Forced together by necessity, however, they will fight through, and learn something about the power of scientific friendship to cross national boundaries.