COL, in physical geography, generally any distinct depression upon a high water-parting offering easy passage from one valley to another. There are numerous cols on the Franco-Italian frontier, e.g., the Little St. Bernard (2,188f t.) which carries the road from the Dora Baltea to the upper Isere. The col (Fr. for "neck," Lat. collum) is usually formed by the headwaters of streams eating backwards towards one another and lowering the water-parting between their valley-heads. In early military operations, the most convenient col controlled the route of the army's movement.