i88 A TROPICAL DEPENDENCY mation, King John was preparing the expedition of Vasco da Gama at the time that Askia was in Cairo. The interest aroused by the discoveries of Columbus must have been great in Arabian as well as European circles.

The geographers of the East must have believed that he had reached the eastern shores of Asia, and as they were well acquainted with the geography of Asia to the farthest limits of China and Japan, they must have been greatly exercised to account for the discrepancy apparently displayed in the size of the world as long since measured by the astronomers of India, and corrected and accepted by the scientific observations of Greeks and Arabs. These matters must have been subjects of discussion in intelligent circles in Cairo during the visit of the Askia, and he must presumably have shared in the general interest which they excited.

He returned to the Soudan in 1497, too early to have heard of the result of the expedition of Vasco da Gama, which in November of that year attained the object for which it was despatched, and succeeded in doubling the Cape of Good Hope. This last event was one of supreme importance to the history of the Soudan, for it opened the passage of the Atlantic to European commerce ; and, in conjunction with the almost simultaneous closing of the northern ports of Africa to Christian intercourse, it determined the fact that the subsequent approach of Europe to West Africa should be from the south by sea, instead of, as in all the previous chapters of Soudanese history, from the north by land. The frontage of the Soudan upon civilisation was reversed.

But, as has been seen, the southern portion of West Africa, following the sinuosities of the Gulf of Guinea, is cut off from the healthier uplands by a swampy belt of densely wooded malarial jungle, backed by a continuous range of hills. This swampy belt was, at the end of the fifteenth century, as it had been from immemorial antiquity, the habitation of pagans, who, in the estimation of their Arab chroniclers, represented the