There is one point of resemblance for the historian between Arabia and China, for in both we see the still natural and spontaneous survival of national life and habits which have endured, without essential change, for something like four thousand years. Arabia is even the more valuable monument of the two, for Chinese conservatism, as will be seen, does not exclude a slow and gradual evolution, while in the more secluded parts of Arabia, the most civilized tribesmen are still, so far as we can judge, at exactly the same level as the majority of their ancestors four thousand years ago.

All travellers insist on the exhilarating qualities of the desert air, and on the sanitary influence of its intense dryness. The carcasses of dead camels dry up innocuously by the wayside; the Arab tent is innocent even of fleas; at Sana, nearly in the same latitude as Senegal, the mediæval geographer, Hamdani, recorded as a marvel that meat would keep good for three or four days in the butchers' shops; and, in general, the Bedouin are exempt from all those human ills which modern science traces to the multiplication of microbes in damp-bred decay. Life in pure, dry air, such as desert tribes enjoy as fully as Alpine mountaineers, conduces to the vigour of the race, which does not depend for its vitality on renewal from without; while the increase of population, for which there is no room at home, overflows sometimes in the shape of conquering hordes, sometimes in a more pacific, perennial stream of emigrant traders.