The movements of peoples constantly recur to these old grooves.  The unmarked path of the voyageur’s canoe, bringing out pelts from Lake Superior to the fur market at Montreal, is followed to-day by whaleback steamers with their cargoes of Manitoba wheat.  To-day the Mohawk depression through the northern Appalachians diverts some of Canada’s trade from the Great Lakes to the Hudson, just as in the seventeenth century it enabled the Dutch at New Amsterdam and later the English at Albany to tap the fur trade of Canada’s frozen forests.  Formerly a line of stream and portage, it carries now the Erie Canal and New York Central Railroad.[2] Similarly the narrow level belt of land extending from the mouth of the Hudson to the eastern elbow of the lower Delaware, defining the outer margin of the rough hill country of northern New Jersey and the inner margin of the smooth coastal plain, has been from savage days such a natural thoroughfare.  Here ran the trail of the Lenni-Lenapi Indians; a little later, the old Dutch road between New Amsterdam and the Delaware trading-posts; yet later the King’s Highway from New York to Philadelphia.  In 1838 it became the route of the Delaware and Raritan Canal, and more recently of the Pennsylvania Railroad between New York and Philadelphia.[3]

The early Aryans, in their gradual dispersion over northwestern India, reached the Arabian Sea chiefly by a route running southward from the Indus-Ganges divide, between the eastern border of the Rajputana Desert and the western foot of the Aravalli Hills.  The streams flowing down from this range across the thirsty plains unite to form the Luni River, which draws a dead-line to the advance of the desert.  Here a smooth and well-watered path brought the early Aryans of India to a fertile coast along the Gulf of Cambay.[4] In the palmy days of the Mongol Empire during the seventeenth century, and doubtless much earlier, it became an established trade route between the sea and the rich cities of the upper Ganges.[5] Recently it determined the line of the Rajputana Railroad from the Gulf of Cambay to Delhi.[6] Barygaza, the ancient seaboard terminus of this route, appears in Pliny’s time as the most famous emporium of western India, the resort of Greek and Arab merchants.[7] It reappears later in history with its name metamorphosed to Baroche or Broach, where in 1616 the British established a factory for trade,[8] but is finally superseded, under Portuguese and English rule, by nearby Surat.  Thus natural conditions fix the channels in which the stream of humanity most easily moves, determine within certain limits the direction of its flow, the velocity and volume of its current.  Every new flood tends to fit itself approximately into the old banks, seeks first these lines of least resistance, and only when it finds them blocked or pre-empted does it turn to more difficult paths.

[Sidenote:  Regions of historical similarity.]