First, a face of rock, very steep, and in some places almost perpendicular; secondly, a regular talus of fallen rocks, stones, etc., as shown in the view of the Rhone Valley (Fig. 26), which takes what is known as the slope of repose, at an angle which depends on the character of the material. As a rule for loose rock fragments it may be taken roughly to be an angle of about 45 deg.. Then an irregular slope followed in many places by one or more terraces, and lastly the present bed of the river. [Illustration: Fig. 28.--Diagram of an Alpine valley showing a river cone. Front view.] The width or narrowness of the valley in relation to its depth depends greatly on the condition of the rocks, the harder and tougher they are the narrower as a rule being the valley. From time to time a side stream enters the main valley. This is itself composed of many smaller rivulets. If the lateral valleys are steep, the streams bring with them, especially after rains, large quantities of earth and stones. When, however, they reach the main valley, the rapidity of the current being less, their power of transport also diminishes, and they spread out the material which they carry down in a depressed cone (Figs. 28, 29, 31, 32). A side stream with its terminal cone, when seen from the opposite side of the valley, presents the appearance shown in Figs. 28, 31, or, if we are looking down the valley, as in Figs. 29, 32, the river being often driven to one side of the main valley, as, for instance, is the case in the Valais, near Sion, where the Rhone (Fig. 30) is driven out of its course by, and forms a curve round, the cone brought down by the torrent of the Borgne. [Illustration: Fig. 29.--Diagram of an Alpine valley, showing a river cone. Lateral view.] Sometimes two lateral valleys (see Plate) come down nearly opposite one another, so that the cones meet, as, for instance, some little way below Vernayaz, and, indeed, in several other places in the Valais (Fig. 31). Or more permanent lakes may be due to a ridge of rock running across the valley, as, for instance, just below St. Maurice in the Valais. [Illustration: Fig. 30.] [Illustration: VIEW IN THE VALAIS BELOW ST. MAURICE. _To face page 266._] [Illustration: Fig. 31.--View in the Rhone Valley, showing a lateral cone.] Almost all river valleys contain, or have contained, in their course one or more lakes, and where a river falls into a lake a cone like those just described is formed, and projects into the lake. Thus on the Lake of Geneva, between Vevey and Villeneuve (see Fig. 33), there are several such promontories, each marking the place where a stream falls into the lake. [Illustration: Fig. 32.--View in the Rhone Valley, showing the slope of a river cone.] The Rhone itself has not only filled up what was once the upper end of the lake, but has built out a strip of land into the water. [Illustration: Fig. 33.--Shore of the Lake of Geneva, near Vevey.]