The Atlantic, now that they were about to leave it, made them a gift of some magical moments. One calm dry day a myriad butterflies came streaming past them far out at sea. It was like a snowstorm; as far as one could see, even with the aid of a telescope, the sky was filled with soft, white, fluttering wings, and it was not until the evening that a wind came up and blew them away.

Then one night they found themselves sailing along in a sea of gold: "The vessel drove before her bows two billows of liquid phosphorus, and in her wake she was followed by a milky train. As far as the eye could reach the crest of every wave was bright . . ."

Christmas Day, 1833, found themfar down the coast in the estuary of the Desire River, and it was the best Christmas they had in the whole five years' voyage. Darwin had shot a 170-lb guanaco on the day before, so there was fresh meat for every man. In the afternoon the crews of both ships came ashore for a contest of wrestling, jumping and running: "Old men with long beards and young men without them were playing like so many children." FitzRoy, in a benign mood, presented the prizes. It was all very different, Darwin remarks, from the usual Christmas celebration, every man getting as drunk as he could.

Physically Darwin was growing much stronger, stronger even than many of his shipmates, who were not able to climb mountains and stretch their legs on shore as he was. "The greatest luxury," he wrote, "is a shingle beach for a bed ... I am quite astonished to find I can endure this life; if it was not for the strong and increasing pleasure from Natural History I never could" (Figure 1, Midshipman’s Berth). But he was very tough. Witness the little incident that occurred one day when they were anchored at St Julian, a particularly arid stretch of the Patagonian coast; no trees, no bird or beast except for a sentinel guanaco. "All was stillness and desolation. One reflected how many ages the plain had thus lasted, and how many more it was doomed thus to continue." With FitzRoy and a party of men Darwin went ashore to search for a freshwater source which was marked on an old Spanish map. It was overwhelmingly hot, they were laden with instruments and guns, and after some hours of tramping across the plain all except Darwin were too exhausted to continue. However, from a hilltop they could see what appeared to be some lakes about two miles distant, and Darwin went off to explore. They watched anxiously while he stooped down at the first lake and then immediately got up and went on to another, where the same thing happened. Darwin walked slowly back with the news that the water was salt.

They were now in a serious situation. FitzRoy and one of the sailors were still quite unable to move and seemed to be getting worse. Darwin did not much like leaving them with the vultures gathering ominously round, but there was nothing for it but to return to the ship for help. He set off on a forced march with the others, and by the time they had reached the Beagle long after dark he had been on his feet continuously for eleven hours without water. A rescue party brought back FitzRoy and the sailor before morning.

. . . And so it was a gloomy and storm-battered little ship that arrived at last off Valparaiso (the Valley of Paradise) on 22 July 1834. (Figure 2, Map Showing Valparaiso on West Coast of S. America.) But the sea was calm, the sun was shining at last, and after eight months out of touch with the world - eight months of monotonous food, of wet clothes and the perpetual heaving of the deck - it was an exhilarating thing for them to see a civilised town again, especially such a beautiful town as this. The white flat-topped houses straggled up the mountainside among trees and patches of green grass, and behind it rose up the tremendous backcloth of the Andes. (Figure 3, The Port of Valparaiso.) Good country smells came out from the shore, and the smoke from the homestead chimneys was a promise of fresh food and the sight of women once again. Letters from home were awaiting them, the third volume of Lyell's Geology had arrived, and even Darwin's walking shoes were in the packages from England. He lost no time in getting off the dank ship and taking up his quarters with Richard Corfield, an old school fellow he found living in the town. Then he was off on a mule to unravel the mystery of the Andes. He was away for six weeks.

There is something about Darwin's travels in the high Cordillera - and he made several trips there - that is especially sparkling and fresh. Of course he loved mountain climbing, but the Andes lifted up his spirits to the highest pitch, ideas crowded into his mind, one discovery led to another, and he was game for anything.

He stands on a crag high above Valparaiso, nothing around him but bare red rocks and the condors wheeling overhead, and the clarity of the air is such that Chile spreads out below as though it were a map. He can see the masts of the ships at anchor in the bay, 26 miles away. Behind him a "fine chaos of mountains" spreads away. It is sublime, "like hearing a chorus of the Messiah in full orchestra. I felt glad that I was alone." In the teeth of a high wind coming in from the Pacific he sits his mule securely, and even on the most vertiginous passes and the most wobbly of suspension bridges he feels no giddiness. (Figure 4, Darwin Travelling in the Andes.) They are so high up that their potatoes boil but will not cook, and he must huddle up to his two guides for warmth at night, but the usual mountain sickness does not touch him.

There is so much to see: the alpine birds, especially the little tapaculo or "cover up your posterior" bird that hopped about with its tall erect (Figure 5, The Tapaculo), and the turco, a ridiculous figure with its stilt-like legs popping from one bush to another with uncommon quickness; the puma which is driven up a tree and baited to death by the dogs, but utters no cry; the rat, very tame and abundant, that lives "chiefly in hedges, curling its tail." He saw what he thought was a cloud of heavy smoke, which turned out to be a swarm of locusts, flying north at a speed of some ten miles an hour. The great swarm, 2000 feet thick, came rushing on with a sound like wind going through the rigging of a ship, and Darwin joined the peasants in shouting and waving branches about in a vain effort to drive them away.

But it is the geology of the mountains that engrosses him, and he makes two discoveries that rivet his attention: at 12,000 feet he comes on a bed of fossil seashells (Figure 6, Fossil Sea-Shells Found on the Andes) and then somewhat lower down a small forest of snow white petrified pine trees with marine rock deposits round them. Now at last the "marvellous story" was beginning to unfold. These trees had once stood on the shores of the Atlantic, now 700 miles away; they had been sunk beneath the sea, then raised 7000 feet. Clearly all this part of the South American peninsula was once submerged beneath the sea, and in quite recent geological times had been elevated again. As the Andes were pushed upwards they became at first a series of wooded islands and then a continuous chain of mountains whose cold climate killed off the vegetation as they rose. This movement had been accompanied by earthquakes and volcanic eruptions which acted like safety valves.

Not everyone was going to believe Darwin of course. Some of the Chileans wanted to know what he thought he was doing, roaming around in the mountains with his little hammer. "It is not well," said a suspicious old Spanish lawyer. "Hay un gato encenado aqui (there is a cat shut up here). No country is so rich as to send out people to pick up such rubbish. I do not like it." Darwin replied by asking him if he was not curious to know how the earthquakes and volcanoes occurred, why some springs were hot, others cold. These questions satisfied and silenced most people, but some, however, "like a few in England who are a century behindhand, thought that all such enquiries were useless and impious; and that it was quite sufficient that God had thus made the mountains." And FitzRoy? What was he, with his biblical notions, going to say to all this? Elated and excited by his discoveries Darwin set out for Valparaiso.

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