According to Palander's reductions, the value of a degree in this part of the world was 57037 toises. This was within a toise, the same as was found by Lacaille at the Cape in 1752: thus, at the interval of a century, the French astronomer and the members of the Anglo-Russian Commission had arrived at almost exactly the same result. To deduce the value of the mètre, they would have to wait the issue of the operations which were to be afterwards undertaken in the northern hemisphere. This value was to be the 1/10000000 of the quadrant of the terrestrial meridian. According to previous calculations, the quadrant, taking the depression of the earth into account, comprised 10,000,856 mètres, which brought the exact length of the mètre to .013074 of a toise, or 3 feet 0 inches 11.296 lines. Whether this was correct the subsequent labours of the Commission would have to decide. * * * * * The astronomers had now entirely finished their task, and it only remained for them to reach the mouth of the Zambesi, by following inversely the route afterwards taken by Dr. Livingstone in his second voyage from 1858 to 1864. [Illustration: Descending the Zambesi.] On the 25th of May, after a somewhat laborious journey across a country intersected with rivers, they reached the Victoria Falls. These fine cataracts fully justified their native name, which signifies "sounding smoke." Sheets of water a mile wide, crowned with a double rainbow, rushed from a height twice that of Niagara. Across the deep basalt chasm the enormous torrent produced a roar like peal after peal of thunder. Below the cataract, where the river regained its calmness, the steamboat, which had arrived a fortnight previously by an inferior affluent of the Zambesi, awaited the astronomers, who soon took their places on board. There were two to be left behind. Mokoum and the pioneer stood on the bank. In Mokoum the English were leaving, not only a devoted guide, but one whom they might call a friend. Sir John was especially sorry to part from him, and had offered to take him to Europe, and there entertain him as long as he pleased to remain. But Mokoum had previous engagements; in fact, he was to accompany Livingstone on the second voyage which the brave traveller was about to undertake up the Zambesi, and Mokoum was not a man to depart from his word. He was presented with a substantial recompense, and, what he prized still more, the kind assurances of regard of the Europeans, who acknowledged how much they owed to him. As the steamer left the shore to take the current in the middle of the river, Sir John's last gesture was to wave an adieu to his associate. [Illustration: Adieu to Mokoum.] The descent of the great river, whose banks were dotted with numerous villages, was soon accomplished. The natives, regarding with superstitious admiration the smoking vessel as it moved by mysterious mechanism, made no attempt to obstruct its progress.