We saw, in the second volume of this Greatest Story, Arabs and Moors established along the fertile fringe of Northern Africa. Northward of this fringe lay the Mediterranean; behind it, that is to say to the south, the desert. But the African tribes had penetrated and traversed this desert. They had learnt that there was, on the far side of it, a fertile land again, a land which was later known as Guinea. And this land was watered by a great river, now known as the Senegal river, flowing from the east and coming out into the sea in the Gulf of Guinea. It appeared to come from much the same direction as that in which they rightly supposed lay the sources of the Nile, the river of Egypt; and they seem to have imagined it a western branch of that ancient river. If they could mount up this branch then far enough in their boats they deemed that they might come out on the Nile, and so, if they pleased, arrive again on the Mediterranean. [Sidenote: The land of slaves] Apart from this idea, the land in itself was rich and produced much that they valued--gold dust and ivory in the elephants' tusks which the natives brought or barter with them--but above the ivory and gold and the rest of the rich products they valued the {6} natives themselves, whom they captured and brought to markets in the Mediterranean towns and sold for slaves. Slaves had a value then which is not easy for us to realise to-day when our great difficulty is to find work for men to do. At that time the difficulty was to find men to do the work; and perhaps this was more true of Portugal and Spain than of other European countries, because so much of their territory lay uncultivated and waste by reason of the continual wars which had been waged between the Christians and the Moors. They needed men badly to till those waste lands. This fertile country then, south of the extensive tract of desert, had much that might attract the Spaniard or the Portugee. We do not know very precisely why it was that little Portugal, rather than great Spain, sent out the mariners which worked southward along the western coast of Africa. We do not know, but perhaps we may make a guess. Spain had a large stretch of coast, with many ports, along the Mediterranean, and it is likely that Portuguese vessels would not have been very welcome if they tried to trade in that direction. Moreover, the Mediterranean swarmed with pirates, both of Mahommedan and Christian nations. It was no peaceful sea for the trader. Again, Spain had a long coast line northward and north-eastward right away to where the Pyrenees come up to the Bay of Biscay. There was no warm welcome there for ships encroaching on Spanish trade. Therefore, if the Portuguese sailors were to be adventurous at all there was no other very apparent direction for their enterprise to take than that of the western coast of Africa and of the islands that lay off it, such as Madeira, the Canaries, and the Cape Verde islands.