Beginning then in its cirque, as a river often begins in its lake, the glacier flows downward, river-like, along a course of least resistance. Here it pours over a precipice in broken falls to flatten out in perfect texture in the even stretch below. Here it plunges down rapids, breaking into crevasses as the river in corresponding phase breaks into ripples. Here it rises smoothly over rocks upon its bottom. Here it strikes against a wall of rock and turns sharply. The parallel between the glacier and the river is striking and consistent, notwithstanding that the geologist for technical reasons will quarrel with you if you picturesquely call your glacier a river of ice. Any elevated viewpoint will disclose several or many of these mighty streams flowing in snakelike curves down the mountainside, the greater streams swollen here and there by tributaries as rivers are swollen by entering creeks. And all eventually reach a point, determined by temperature and therefore not constant, where the river of ice becomes the river of water. Beginning white and pure, the glacier gradually clothes itself in rock and dirt. Gathering as it moves narrow edges of matter filched from the shores, later on it heaps these up upon its lower banks. They are lateral moraines. Two merging glaciers unite the material carried on their joined edges and form a medial moraine, a ribbon broadening and thickening as it descends; a glacier made up of several tributaries carries as many medial moraines. It also carries much unorganized matter fallen from the cliffs or scraped from the bottom. Approaching the snout, all these accumulations merge into one moraine; and so soiled has the ice now become that it is difficult to tell which is ice and which is rock. At its snout is an ice-cave far inside of which the resultant river originates.