More important are the rivers that descend from the main chain of the Graian and Pennine Alps and join the Po on its left bank.
The first group of immigrants is said to have crossed the Pennine Alps (Great St Bernard) into the valley of the Po.
It rises at the upper or eastern extremity of the Swiss canton of the Valais, flows between the Bernese Alps (N.) and the Lepontine and Pennine Alps (S.) till it expands into the Lake of Geneva, winds round the southernmost spurs of the Jura range, receives at Lyons its principal tributary, the Saline, and then turns southward through France till, by many mouths, it enters that part of the Mediterranean which is rightly called the Golfe du Lion (sometimes wrongly the Gulf of Lyons).
