Soon after the year 2000 B.C.--so we must conclude--the tribes of South Arabia delivered their spices to the Egyptians, Syrians, and Babylonians, and their incense, which Eastern nations, and in time Western nations also, burned upon the altars of their gods. Then they imported the products of the opposite shore of Africa, a region no less fruitful than South Arabia, and at length the ships of the Indians brought to them the products of the Indus and the Ganges. Thus South Arabia not only exported her own fruits, she became the central mart of East African and Indian products, the point of connection between Eastern and Western Asia. Owing to the fertility of their valleys and terraces, and their old and extensive trade, the tribes of the South soon acquired a more fixed form of constitution and a more advanced civilisation. Numerous remains of magnificent stone structures, ruins of aqueducts, canals, basins, and dams, built with the object of preserving and collecting the water which streamed down the terraces of the mountains and in the valleys, still excite the astonishment of our travellers for the excellence of the plan as well as for the strength of the masonry. The ruins of Nedshran, Sirwah, Ghorab, Nakb-el-Hadshar, and Misenat, and those of Maryab, the old metropolis of the Sabæans, confirm what Western writers and Arab tradition tell us of the glorious palaces of the ancient time and the mighty dams built in the valley of Maryab.[456] The remains of the dams prove that South Arabia, like Egypt and Babylonia, was far better cultivated in those distant times than now; that there also the greatest importance was attached to irrigation, and the inhabitants understood how to preserve and use the water from the mountain-streams on the terraces. The natural assumption that at one time the cultivation of valuable fruits was far more extensive in South Arabia than at present can hardly be incorrect. The inscriptions found in those ruins and elsewhere in the south-west of Yemen, though they do not, so far as is at present ascertained, go back beyond the year 120 B.C.,[457] give us some insight into the nature of the civilisation of these tribes and the ancient form of the South Arabian language and alphabet, which must have grown out of the Phenician at an early date, and then have developed independently beside it.[458] Of a still more recent date, from the first century A.D., we find in the opposite north-west corner of Arabia numerous inscriptions on the rocks in the region of Sinai, written in the North Arabian language and alphabet.[459]