The Franco-Italian linguistic boundary starts at Monte Rosa and extends south, past Gressoney, into the valley of the Doire Baltée, to the town of Settimo Vitone. French has always predominated in this region. It is at present the vernacular of the well-to-do inhabitants and is taught in schools concurrently with Italian. Thence to the west the linguistic boundary passes south of Grand Paradis Peak and attains the political boundary at the sources of the Orco river. Linguistic and political boundaries coincide in the next 27 miles, the line passing through a mountainous and scantily settled region. North of Suse, linguistic and political lines diverge from each other. The former crosses the Doire Ripaire at about five miles east of the town. It then extends in a southerly direction to Pérouse on the Ghison river and traverses the Pellice where the river leaves the highland. The Po is attained near Monte Viso and the political frontier. From the latter peak the line reaches Sampeyre, beyond which it crosses the Stura at Vinadio. The Franco-Italian boundary is reached once more at a few miles east of Lantosque. From here on to the sea Italian speech invades French territory. The structure of the Alps has contributed powerfully to the peopling of a part of the basin of the Po by a Celtic-speaking race. In Turin the name of the Taurins, a Celto-Ligurian tribe, has been preserved to this day. Alpine valleys converge towards the east and diverge towards the west. Human migrations have, therefore, been more intense from west to east than in the opposite direction. Western Piedmont thus passed under French influence after the Middle Ages. At that time the counts of Savoy obtained possession of the country around Suse and Turin. Later they added all of Piedmont to their domain. The upper valley of the Doire Ripaire was part of the French kingdom until the treaty of Utrecht in 1715.