Meridiana by Jules Verne

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.

The geodetic operations were now resumed, and went on as usual till the 28th of June, when they had measured the base of the 15th triangle, which would conclude the second and commence the third degree of the meridian. Here a physical difficulty arose. The country was so thickly covered with underwood, that although the artificial signals could be erected, they could not be discerned at any distance. One station was recognized as available for an electric lamp. This was a mountain 1200 feet high, about thirty miles to the north-west. The choice of this would make the sides of this triangle considerably longer than any of the former, but it was at length determined to adopt it. Colonel Everest, Emery, Zorn, three sailors, and two Bochjesmen, were appointed to establish the lighted signal, the distance being too great to work otherwise than at night.