In a few minutes the yelping ceased, and the bushman and Sir John, who were in advance, were becoming uneasy, when suddenly the barking began again outside the forest, about half a mile away. The horses were spurred in that direction, and soon reached the confines of the marsh. The dog could distinctly be heard, but, on account of the lofty reeds, could not be seen. The riders dismounted, and tied their horses to a tree. With difficulty they made their way through the reeds, and reached a large space covered with water and aquatic plants. In the lowest part lay the brown waters of a lagoon half a mile square. The dog stopped at the muddy edge, and barked furiously. [Illustration: "There he is," cried Mokoum.] "There he is!" cried Mokoum. And sure enough, on a stump at the extremity of a sort of peninsula, sat Nicholas Palander, pencil in hand, and a note-book on his knees, wrapt in calculations. His friends could not suppress a cry. About twenty paces off a number of crocodiles, quite unknown to him, lay watching, and evidently designing an attack. [Illustration: A missing Companion.] "Make haste," said Mokoum, in a low voice; "I don't understand why these animals don't rush on him." "They are waiting till he is gamey," said Sir John, alluding to the idea common among the natives that these reptiles never touch fresh meat. The bushman and Sir John, telling their companions to wait for them, passed round the lagoon, and reached the narrow isthmus by which alone they could get near Palander. They had not gone two hundred steps, when the crocodiles, leaving the water, made straight towards their prey. Palander saw nothing, but went on writing. "Be quick and calm," whispered Mokoum, "or all is lost." Both, kneeling down, aimed at the nearest reptiles, and fired. Two monsters rolled into the water with broken backs, and the rest simultaneously disappeared beneath the surface. At the sound of the guns Palander raised his head. He recognized his companions, and ran towards them waving his note-book, and like the philosopher of old exclaiming "Eureka!" he cried, "I have found it!" "What have you found?" asked Sir John. "An error in the last decimal of a logarithm of James Wolston's." It was a fact. The worthy man had discovered the error, and had secured a right to the prize offered by Wolston's editor. For four days had the astronomer wandered in solitude. Truly Ampère, with his unrivalled gift of abstraction, could not have done better! CHAPTER XII. A STATION TO SIR JOHN'S LIKING. So the Russian mathematician was found! When they asked him how he had passed those four days, he could not tell; he thought the whole story of the crocodiles was a joke, and did not believe it. He had not been hungry; he had lived upon figures. Matthew Strux would not reproach his countryman before his colleagues, but there was every reason to believe that in private he gave him a severe reprimand.