WHEREVER EXTERNAL FACTORS MOVED THE MACHINERY OF change, they began with long-distance trade: with the brave small ships of Indian Ocean sailors, defying the seas of the Zanj, or camel caravans that set their courage against the wastes of the Sahara: with these and their commercial influence, and afterwards their Muslim impact in every field of life.

The trade was old, far older than Islam. By 500 BC, and perhaps long before, Berber enterprise had taken horse-and-chariot trails to the tropical lands beyond. Merchants from Carthage had trafficked down the far west coast. Timgad and Volubilis had been Roman forerunners of Sijilmasa and the great Arabo-Berber entrepots of later times. It was the sea captains of Ptolemaic Egypt who first opened up the East African seaboard.

But the great period of the long-distance trade began with the maturity of Islam after AD 900. Then indeed it spanned the world from Cadiz to Cathay, drawing all Europe within its range and driving far into inland Africa.

Egypt was the pivot of this worldwide system. Thousands of business documents have survived to tell the tale. Fortunately preserved in Cairo for almost a millennium, though only lately available to scholarship, they open the view upon a system of safe and regular travel, long-term credit and long-range dealing, whose size and scope were not again to be achieved for many centuries. Their details are very convincing.

A travel-wearied merchant of Alexandria relaxes in his bath one Friday afternoon towards the year 1100, and then, before sitting down to dinner, scribbles a note to a partner in Cairo. 1 have just arrived from Almeria in Spain. Your business friend in Moroccan Fez sent me there a bar of gold—certainly from the Sudan—so as to buy Spanish silk for you. I thought this not a good idea, however, and am sending you the gold instead. At the same time a friend of your business friend delivered me a certain quantity of ambergris which I also forward herewith. He wants you to send back five flasks of musk of the same value. Please sell the ambergris when you get this letter and buy the musk, because I have to send it off at once.’ Ambergris from tropical African waters, gold from the Western Sudan, silk from Spain, musk from Asia: and all the subject of a small transaction done incidentally for friendship's sake.