The city of Basle stands upon the banks of the Rhine, on the northern frontier of Switzerland. The waters of the Rhine are gathered from hundreds of roaring and turbid torrents which come out, some from vast icy caverns in the glaciers, some from the melting debris of fallen avalanches, some from gushing fountains which break out suddenly through crevices in the rocks or yawning chasms, and some from dark and frightful ravines on the mountain sides, down which they foam and tumble perpetually, fed by vast fields of melting snow above. The waters of all these torrents, being gathered at last into one broad, and deep, and rapid stream, flow to a vast reservoir called the Lake of Constance, where they repose for a time, or, rather, move slowly and insensibly forward, enjoying a comparative quiescence which has all the characteristics and effects of repose. The waters enter this reservoir wild and turbid. They leave it calm and clear; and then, flowing rapidly for one hundred miles along the northern frontier of Switzerland, and receiving successively the waters of many other streams that have come from hundreds of other torrents and have been purified in the repose of other lakes extending over the whole northern slope of Switzerland, they form a broad and rapid river, which flows swiftly through Basle, and then, turning suddenly to the northward, bids Basle and Switzerland farewell together. "And then where does it go?" said Rollo to Mr. George when his uncle had explained this thus far to him. "Straight across the continent to the North Sea," said Mr. George. Thus the whole northern slope of Switzerland is drained by a system of waters which, when united at Basle, form the River Rhine. The morning after Mr. George and Rollo arrived at Basle they were looking out upon the River Rhine from the windows of the hotel. "What a swift river!" said Rollo. "Yes," said Mr. George. "And how blue the water is!" continued Rollo. "Yes," said Mr. George. "The water of the streams which come from the Swiss mountains is turbid at first and very gray from the grinding up of the rocks in the _moraines_ and glaciers and by the avalanches." "What is a moraine?" asked Rollo. "I will explain it to you one of these days," said Mr. George, "when you come to see one." "And a glacier," said Rollo; "what is that?" "I will explain that to you, too, some other time," said Mr. George, "but not now; for the breakfast will come in in a minute or two." "Well," said Rollo, "I can hear while I am eating my breakfast." "That may be," replied Mr. George; "but I cannot lecture very well while I am eating _my_ breakfast." Rollo laughed. "I did not think of that," said he. "What queer boats!" continued Rollo, looking out again upon the river. "And there is a long bridge leading over to the other side. May I go out and walk over on that bridge after breakfast?" "Yes," said Mr. George, "you may go any where you please."