[Sidenote:  Pastoral nomads as middlemen.]

The systematic migrations of nomads, their numerous beasts of burden, and the paucity of desert and steppe products determine pastoral tribes for the office of middlemen;[1149] and as such they appear in all parts of the world.  The contrast of products in arid regions and in the bordering agricultural land, as also in the districts on opposite sides of these vast barriers, stimulates exchanges.  This contrast may rest on a difference of geographic conditions, or of economic development, or both.  The reindeer Chukches of Arctic Siberia take Russian manufactured wares from the fur stations on the Lena River to trade at the coast markets on Bering Sea for Alaskan pelts.  The sons of Jacob, pasturing their flocks on the Judean plateau, saw “a company of Ishmaelites come from Gilead with their camels bearing spicery and balm and myrrh, going to carry it down to Egypt."[1150] This caravan of Arabian merchants purchased Joseph as a slave, a characteristic commodity in desert commerce from ancient times to the present.  The predatory expeditions of nomads provide them with abundant captives, only few of which can be utilized as slaves in their pastoral economy.  In the same way the Kirghis manage the caravan trade between Russia and Bukhara, sometimes adding captured travelers to their other wares.  In ancient times Nubian shepherd folk acted as migrant middlemen between Egypt and Meroe near the junction of the Atbara River and the Nile, as did also the desert tribe of the Nasamones between Carthage and interior Africa.[1151] From remote ages an active caravan trade was carried on between the productive districts of Arabia Felix and the cities of Mesopotamia, Syria and Egypt.  Mohammed himself was a caravan leader; in the faith which he established religious pilgrimages and commercial ventures were inextricably united, while to the mercantile spirit it gave a fresh and vigorous impetus.[1152] The caravan trade of the Sahara was first organized by Moorish and Arab tribes who dwelt on the northern margin of the desert, rearing herds of camels.  These they hired to merchants for the journey between Morocco and Timbuctoo, in return for cereals and clothing.  Hence Morocco has been the chief customer of the great desert town near the Niger, and sends thither numerous caravans from Tendouf (Taredant) Morocco, Fez and Tafilet.  Algiers dominates the less important route via the oasis of Twat, and Tripolis that through Ghadames to the busy towns in the Lake Chad basin.[1153]

[Sidenote:  Desert markets.]

If the camel is “the ship of the desert,” the market towns on the margin of the sandy wastes are the ports of the desert.  Their bazaars hold everything that the nomad needs.  Their suburbs are a shifting series of shepherd encampments or extensive caravanseries for merchant and pack animal, like the abaradion of Timbuctoo, which receives annually from fifty to sixty thousand camels.[1154] Their industries