Those who have followed up the Inn from the beautiful mountain-girt capital of Tirol, which is named from bridging it, will not willingly forgo a pilgrimage to the little Lago di Lunghino, which is its reputed source. It is an imposing cradle for a great river, lying under a sheer wall of rock that rises into stony spires. The little stream escapes from its austere birthplace under a bridge of frozen snow, and flings itself, wild and white, down the steep descent to its lakes. In the first instance it was probably one of the most modest affluents of the stream it is now taken to represent. Both its slender volume and the fact that its direction is different to that of the Inn preclude its being considered in any real {26} sense the source of the great stream that hollowed the Engadine, which now lies a truncated trough with no terminal amphitheatre. The original source and all the upper affluents of this mighty river that rolled to the Black Sea have long since been captured by the Maira and diverted to the Mediterranean. If we walk up the neighbouring Piz Lunghino we shall look down on the field of that long battle of the waters. It is the most striking example to be found of the slow but steady encroachment of the southern streams that is going on all along the Alps. The more abrupt slope on the south gives the water greater erosive force, with the result that it is continually eating back into the range and thrusting the watershed to the north. Nowhere has this result been so extensive and startling as in the region below us.* * The remarkable record of this physiographical change preserved in the present flora of the valley is noticed in the chapter on botany in 'Upper Engadine.' Heim, a great authority, thinks that the original source of the great river that carved the Engadine was some seven or eight miles away in the Val Marozzo, which now passes for the head of the Val Bregaglia, whose normal direction seems thus reversed. The main water-shed of the Alps must then, he thinks, have lain along a transverse ridge somewhere above Vicosoprano. The head waters of the Maira gradually ate through this and, by offering to those of the Inn {27} a more rapid descent, captured them for the Mediterranean. The Engadine lakes were thus bereft of their parent source; the current from the rivulet of the Lunghino tarn was quite unequal to sweeping down the detritus brought by its furious affluents, which were thus free to form the deltas that are gradually filling the lakes, whose fate, happily remote, would seem to be to disappear.