The Eastern Empire on the other hand shows at first glance a remarkable lack of flat land and a great number of mountains. The Balkan peninsula, for instance, is almost entirely composed of chains of mountains which cross and recross in such a manner as to render exploration very difficult; even up to the present day little is known of the country. Owing to the mountainous character of the Balkan peninsula only a portion of the ground (of which to-day 30 per cent. is unproductive in Turkey, but in Greece quite 58.9 per cent.) could be cultivated. The expansive north was so favourable to the cultivation of corn, especially in the valleys near the rivers, that Thrace once enjoyed the distinction of producing the finest and heaviest wheat for exportation to Greece; whilst in Greece itself only Thessaly and Bœotia were noted for their agricultural soil, the remaining districts being best suited to pasture land for cattle. Furthermore, in Asia Minor and on the east coast of the Mediterranean but a part of the land repays the trouble of cultivation, for it is only the western valleys of the rivers emptying themselves into the Ægean Sea and the northern border of the Black Sea which yield good harvests of wine, oil, and corn; for the Mediterranean coast, with the exception of the rich district of Adana, offers no specially productive ground. The eastern portion of the Roman Empire, though certainly far behind the west not only in size but also in its products, enjoyed in other ways many advantages denied to the Occident. On account of the vastness of the Western Empire the various cities and places of importance were widely scattered and separated from the chief centre by great distances, which arrangement was undoubtedly advantageous to discontented legions and ambitious officers desirous of revolting against the lawful head of the state. The wide expanse to the northwest, however, occasioned a fatal lengthening of the eastern border line guarded by the easily crossed Rhine and Danube. The Orient, on the contrary, had its sole coast-line bound by the Mediterranean, a much navigated and frequented sea. No city or town was separated from the others by long stretches of land, for the sea enabled the troops from one garrison to reach another in a few days. The Danube was a weak defence against the barbarians marching from the north, and the natural highway of Baku would not lead invaders into the valley of a river opening into Asia Minor, but straight into Armenia, which being full of chasms and ravines, was easy to defend. Even in the case of an invasion from the north the whole of the East, excepting Egypt, would offer but wild uninhabited country to the enemy.