Meantime a similar spirit of expansion was manifesting itself along the southern borders of the future colonial empire. Guinea and the Ivory Coast had been annexed in 1843. The expeditions of Savargnan de Brazza in the late seventies and early eighties won for France the vast territory which is now known as French Equatorial Africa. In 1887 the Binger expedition gave a decided stimulus to French enterprise in West Africa by linking together the hinterlands of Senegambia and the Ivory Coast. French gunboats were a-prowl up the Niger and the Senegal seeking further opportunities to plant the tricolor. Thenceforward the occupation of the interior was swift and uninterrupted, a long series of expeditions pushing the French frontiers northward and eastward until they occupied the whole bend of the Niger and flowed around the British colony of Nigeria to join, at Lake Tchad, with the French Congo advancing from the south. From all sides the French colonies, north, west, and south, were pushing forward in a simultaneous advance. The foundations of this vast colonial structure having thus been completed, the corner-stone was officially laid in 1890, when, by the signing of the Anglo-French Convention, England formally recognized France’s claim to all that portion of the Sahara lying between the Algerian-Tunisian frontiers on the north and a line drawn from Say, a town on the Niger, to Lake Tchad on the south. When, by this treaty, France secured her claim to the Sahara, Lord Salisbury remarked dryly that “the French cock seems to enjoy scratching in the sand.” [Illustration: THE SANDY SEA In parts, but not throughout, the Sahara resembles a frozen ocean, its tremendous billows of gray-white sand seemingly arrested in the very act of breaking. But by far the greater part is not sandy at all; rather, a series of undulating steppes, strewn with broken stone, dotted with oases, and broken by numerous mountain chains, some of which are upward of a mile in height] Though the territory lying within the great bend of the Niger, embraced in what is now the French Sudan, was occupied in 1893, and though two years later the tricolor was hoisted over the mud-walled citadel of Timbuktu, the great caravan-center and trade-mart of the south, it was not until the very close of the nineteenth century that the central Sahara was crossed by Europeans. This remarkable journey was made by Fernand Foureau, the greatest of all the long line of French African explorers, who, setting out from Algeria with a small military escort, succeeded in reaching Zinder, an important trade center on the Nigerian frontier, in November, 1899.