Nothing in the history of the world is more surprising than the rapid spread of Arab conquests in Asia, Africa, and Western Europe at the close of the seventh century of our era, excepting, perhaps, the thoroughness of the subsequent disappearance of Arab influence, and the absolute effacement of the Arabic language in those countries which Arabs ruled and robbed. In Persia, Makran, Central Asia, or the Indus valley, hardly a word of Arabic is now to be recognized. Geographical terms may here and there be found near the coast, surviving only because Arab ships still skirt those shores and the sailor calls the landmarks by old-world names. Even in the English language the sea terms of the Arab sailor still live. What is our "Admiral" but the "Al mir ul bahr" of the Arabian Sea, or our "Barge" but his "Barija," or warship! But in Sind, where Arab supremacy lasted for at least three centuries, there is nothing left to indicate that the Arab ever was there.
The effacement of the Arab in India is chiefly due to the Afghan, the Turk, and the Mongol. Mahmud of Ghazni put the finishing blow to Arab supremacy in the Indus valley, when he sacked Multan about the beginning of the eleventh century; and subsequently the destroying hordes of Chenghiz Khan and Tamerlane completed the final downfall of the Empire of the Khalifs.
Between the beginning of the eighth century and that of the eleventh the whole world of the Indian north-west frontier and its broad hinterland, extending to the Tigris and the Oxus, was much traversed and thoroughly well known to the Arab trader. In Makran we have seen how they shaped out for themselves overland routes to India, establishing big trade centres in flourishing towns, burying their dead in layers on the hill-sides, cultivating their national fruit, the date, in Makran valleys, and surrounding themselves with the wealth and beauty of irrigated agriculture. The chief impulse to Arab exploration emanated from the seat of the Khalifs in Mesopotamia, and the schools of Western Persia and Bagdad appear to have educated the best of those practical geographers who have left us their records of travel in the East; but there are indications of an occasional influx of Arabs from the coasts of Southern Arabia about whom we learn nothing whatever from mediæval histories. It will be at any rate interesting to discuss the general trend of exploration and travel, associated either with pilgrimage or commerce, which distinguished the days of Arab supremacy, and which throws considerable light on the geography of the Indian borderland before its political features were rearranged by the hand of Chenghiz Khan and his successors. This has never yet been attempted by the light of recent investigations, and even now it can only be done partially and indifferently from the want of completed maps. The borderland which touches the Arabian Sea--Southern Baluchistan--has been completely explored and mapped, and the more obvious inferences to be derived from that mapping have already been made. But Seistan, Karmania, the highways and cities of Turkistan (Tocharistan) and Badakshan have not, so far as I know, been outlined in any modern work based on Arab writings and collated with the geographical surveys of the Russo-Afghan Boundary Commission and their reports. It was after all but a cursory examination of a huge area of most interesting country that was possible within the limited time devoted to boundary demarcation labours in 1883-85; but the physical features of this part of Asia being now fairly well defined, there is a good deal to be inferred with reasonable probability from the circumstance that highways and cities must ever be dependent for their location on the distributions of topography.