Let us now turn to the valleys in a recently glaciated country. We omit any description of existing glaciers; these will be found described in the volume on the Alps, and further, photography and the picture postcard have rendered the main features of a glacier familiar to every one. Almost every large railway station now shows fine coloured photographs of some of the important Swiss glaciers. Taking, then, a valley known to have been occupied by a Pleistocene glacier, we find the following features. As contrasted with an ordinary river valley, the glacial valley is usually flat-bottomed, a condition described as U-shaped to point the contrast with the river valley. Examples in Great Britain and elsewhere are frequent, but some of the Alpine valleys show the phenomenon in a very striking form. Two good examples are the Aar valley at Meiringen, and the Lauterbrunnen valley at the village of the same name. Both have been rendered more or less familiar by constant photographing (see fig. 7). The reason why they have been so much photographed leads us to consider another peculiarity of the glaciated valley. In both the cases named a steep cliff wall rises from either side of the broad, flat valley floor, and from the summit of this cliff the lateral streams leap into the main valley by often superb waterfalls. This is a very important feature of glaciated valleys--the fact that their tributaries are markedly _discordant_, that is, that there is marked difference of level between the beds of the side and main streams. Because the side valleys lie high above the main they are said to "hang," and are called hanging valleys, while the main valley is said to be over-deepened. The rocky height over which the water springs may be called the junction step, as an attempt to translate the French term _gradin de confluence_ which is applied to it. Incidentally we may note that in the Alps the junction step is of great human importance. Its presence gives the water the power which is used in lighting the Alpine villages with electricity, and in driving the trains which often carry the tourist to those villages. In the French and Italian Alps especially, the power is being more and more used to supply the motive force for various minor manufactures, notably for the production of nitrogenous manure from the air. [Illustration: Fig. 6.--A diagrammatic cross-section of a recently glaciated valley. AB, the mountain slope which rose above the ancient glacier and has therefore retained the sharp, unrounded forms due to ordinary weathering. BC, the shelf or shoulder, formerly covered by the ice, and therefore strewn with glacial débris. It now usually forms a pasture or alp. The dotted line connecting CC shows the probable form of the pre-glacial valley; CD, the rocky wall of the existing U-shaped valley on whose floor the river now flows.]