=The mountain rampart and its portals.=—As soon as we examine the coastal belt we observe that the “Great Ice” of Greenland is held in by a wall of mountains and so prevented from spreading out to its natural surface in the marginal portions. Through portals of the inclosing mountain ranges—the _outlets_—it sends out _tongues_ of ice which in many respects resemble certain types of mountain glaciers. [Illustration: FIG. 300.—Profile in natural proportions across the southern end of the continental glacier of Greenland, constructed upon an arc of the earth’s surface and based upon Nansen’s profile corrected by Hess. The marginal portions of the profile are represented below upon a magnified scale in order to bring out the characters of the marginal slopes.] Such measurements as have been made upon the inland ice of Greenland at points back from, but yet comparatively near to, the outlets, show that it has here a surface rate of motion amounting to less than an inch per day, and it is highly probable that at moderate distances from the margin this amount diminishes to zero. Upon the outlets, on the contrary, surface rates as high as 59 feet per day have been measured, and even 100 feet per day has been reported. We are thus justified in saying that glacier flow within the outlets is from 700 to 1000 times as great as it is upon the near-by inland ice, and that the glacier is in a measure drained through the portals of the inclosing ranges. Back from these outlet streams of ice, or tongues, the surface of the inland ice is depressed to form a dimple or “basin of exudation” as is the surface of a reservoir above the raceway when the water is being rapidly drawn away (Fig. 301). ┌────────────────────────────────────────────────────────────────────┐ │ PLATE 13. │ │ │ │ [Illustration: _A._ Precipitous front of the Bryant glacier outlet │ │ of the Greenland inland-ice (after Chamberlin).] │ │ │ │ [Illustration: _B._ Lateral stream beside the Benedict glacier │ │ outlet, Greenland (after R. E. Peary).] │ └────────────────────────────────────────────────────────────────────┘ [Illustration: FIG. 301.—Map of a glacier tongue, with dimple showing above and due to indraught of the ice. Umanakfjord, Greenland (after von Drygalski).] Fissures in the ice, the so-called crevasses, are the recognized marks of ice movement, and these are always concentrated at the steep slopes of the ice surface in the neighborhood of its margins. Upon the Greenland ice, crevasses are restricted in their distribution to a zone which extends from seven to twenty-five miles within the ice border.