The northern limit of the Mediterranean race in Spain lies sharply defined along the crest of the Pyrenees, whose long unbroken wall forms one of the most pronounced boundaries in Europe;[182] yet traders and smugglers have pushed their way through from time immemorial.

Long after Etruscan merchants had crossed northward over the Alps, Roman expansion and colonization made a detour around the mountains westward into Gaul, with the result that the Germans received Roman civilization not straight from the south, but secondhand through their Gallic neighbors west of the Rhine.
[Sidenote: Commerce a guide to various movements.] Commerce, though differing from other historical movements, may give to these direction and destination.

The trader is frequently the herald of soldier and settler.

He becomes their guide, takes them along the trail which he has blazed, and gives them his own definiteness of aim.

The earliest Roman conquest of the Alpine tribes was made for the purpose of opening the passes for traders and abolishing the heavy transit duties imposed by the mountaineers.[183] Fur-traders inaugurated French expansion to the far west of Canada, and the Russian advance into Siberia.