of the Danube from its source to Vienna, and as just mentioned, of the Aar from Bern to Waldshut. Hence also, whenever the Swiss rivers running east and west break into a transverse valley, as the larger ones all do, and some more than once, they invariably, whether originally running east or westwards, turn towards the north.

But although we thus get a clue to the general structure of Switzerland, the whole question is extremely complex, and the strata have been crumpled and folded in the most complicated manner, sometimes completely reversed, so that older rocks have been folded back on younger strata, and even in some cases these folds again refolded. Moreover, the denudation by aerial action, by glaciers, frosts, and rivers has removed hundreds, or rather thousands, of feet of strata. In fact, the mountain tops are not by any means the spots which have been the highest, but those which were originally least denuded; and hence it is that so many of the peaks stand at about the same altitude.

THE CONFLICTS AND ADVENTURES OF RIVERS

Our ancestors looked upon rivers as being in some sense alive, and in fact in their "struggle for existence" they not only labour to adapt their channel to their own requirements, but in many cases enter into conflict with one another.

In the plain of Bengal, for instance, there

three great rivers, the Brahmapootra coming from the north, the Ganges from the west, and the Megna from the east, each of them with a number of tributary streams. Mr. Fergusson1 has given us a most interesting and entertaining account of the struggles between these great rivers to occupy the fertile plain of Bengal.

The Megna, though much inferior in size to the Brahmapootra, has one great advantage. It depends mainly on the monsoon rains for its supply, while the Brahmapootra not only has a longer course to run, but relies for its floods, to a great extent, on the melting of the

1 Geol. Jour., 1863.

snow, so that, arriving later at the scene of the struggle, it finds the country already occupied by the Megna to such an extent that it has been driven nearly 70 miles northwards, and forced to find a new channel.

Under these circumstances it has attacked the territory of the Ganges, and being in flood earlier than that river, though later than the Megna, it has in its turn a great advantage.

Whatever the ultimate result may be the struggle continues vigorously. At Sooksaghur, says Fergusson, "there was a noble country house, built by Warren Hastings, about a mile from the banks of the Hoogly. When I first knew it in 1830 half the avenue of noble trees, which led from the river to the house, was gone; when I last saw it, some eight years afterwards, the river was close at hand. Since then house, stables, garden, and village are all gone, and the river was on the point of breaking through the narrow neck of high land that remained, and pouring itself into some weak-banded nullahs in the lowlands beyond: and if it had succeeded, the Hoogly would

have deserted Calcutta. At this juncture the Eastern Bengal Railway Company intervened. They were carrying their works along the ridge, and they have, for the moment at least, stopped the oscillation in this direction."

Similar causes have affected many of the other tributaries of the Ganges, so that the survey made by Rennell in 1780-90 is no longer any evidence as to the present course of the rivers. They may now be anywhere else; in some cases all we can say is that they are certainly not now where they were then.

The association of the three great European rivers the Rhine, the Rhone, and the Danube with the past history of our race, invests them with a singular fascination, and their past history is one of much interest. They all three derive part of their upper waters from the group of mountains between the Galenstock and the Bernardino, within a space of a few miles; on the east the waters now run into the Black Sea, on the north into the German Ocean, and on the west into the Mediterranean, But it has not always been so.

At present the waters of the Valais escape from the Lake of Geneva at the western end, and through the remarkable defile of Fort de l'Ecluse and Malpertuis, which has a depth of 600 feet, and is at one place not more than 14 feet across. Moreover, at various points round the Lake of Geneva, remains of lake terraces show that the water once stood at a level much higher than the present. One of these is rather

more than 250 feet1 above the lake.

A glance at the map will show that between Lausanne and Yverdun there is a low tract of land, and the Venoge, which falls into the Lake of Geneva between Lausanne and Morges, runs within about half a mile of the Nozon, which falls into the Lake of Neuchâtel at Yverdun, the two being connected by the Canal d'Entreroches, and the height of the watershed being only 250 feet above the lake, corresponding with the abovementioned lake terrace. It is evident, therefore, that when the Lake of Geneva stood at the level of the 250-feet terrace the waters ran out,

1 Favre, Rech. Geol. de la Savoie.