Eurasian waterways was "undertaken by this race in the course of its westerly spread. 2
This specific case of migration may be considered as part of the powerful "trans-humanizing" process moving in an east-west direction which has taken place on the Eurasian continent. Interdependence be- tween this movement and the conformable trend of the main lines of Eurasian structure as well as correlated climatic zones still remains to be determined. Ultimately the entire problem may be found to be con- nected to mechanical effects of our planet's rotation.
Since the dawn of historical times the Propontine area and its outlets have borne the vessels of adventurous traders and colonists. Early ex- tension of Hellenic influence to the easternmost shore of the Black Sea was rendered possible by the advantages offered by this water route to Greek pioneers. The foundation of Byzantium in 657 B.C. promoted the intercourse between the east and west which at that time was largely restricted to relations between the iEgean and Black Seas. A half-way station was established on the unique site of the modern capital of the Sultans. Here a system of powerful defenses reinforced by the en- circling waters of the Golder Horn, Bosporus and Marmora provided long lease of existence to the city which both Europeans and Asiatics regarded as the gateway to rival continents.
Between the iEgean mouth of the Hellespont and the Euxine out- let of the Bosporus, Asiatic invaders of the western world and European colonizers of the east have always found the shortest watery stretch of their respective routes. This was an important point at a time when control of natural forces was in a still undeveloped stage. The danger of impairing the cohesive strength of an army of invaders was also minimized.
These considerations probably led Darius to adopt the Bosporus route in the expedition sent against the Scythians in 513 B.C. His cohorts tramped from Asia into Europe over a bridge of boats thrown across the Bosporus in that year. 3 From that time on various incursions of Asiatics into the western continent were to cross the water of these straits.
During the second Persian war the bridging of the Hellespont by Xerxes' generals is commonly reported as having been undertaken be- tween Abydos and Madytus. Both of these sites lie north of the nar- rowest section of the Dardanelles, — the Kilidbahr-Chanak gap, barely a mile in width. They correspond approximately to Nagara Point and the paltry hamlet of Maitos, between which the distance of the straits attains three miles. The current at the wider section is not as swift.
2 Cf. map of Asiatic Migrations in The Wanderings of Peoples, by A. C. Haddon, Cambridge, 1912.
3 Herod., B. IV., 86-89.