At the borders of arctic glaciers the lower layers are not infrequently upturned, as shown in Figs. 269 to 272. Where the layers turn up at the end of a glacier (Figs. 269 and 270), basal and englacial débris is carried to the surface by actual upward movement, and a terminal moraine or a series of terminal moraines sometimes aggregated _where the upturned layers of ice outcrop at the surface_ (Fig. 271). That the material of these moraines was originally basal is abundantly demonstrated by the bruised and scratched condition of the bowlders and pebbles, and sometimes by the nature of the material itself. For example, in two cases in North Greenland where glaciers descend into the heads of shallow bays and move forward on their bottoms, moraines formed by the upturning of the layers were seen to contain _abundant molluscan shells derived from the bottom of the bay_. The upturning sometimes affects the side-edges of ice-tongues (Fig. 272) as well as their ends, and the material thus brought to the surface gives origin to lateral moraines altogether different in origin from the lateral moraines formed by the falling of débris upon the glaciers. Sometimes also there is an upturning of the ice along a longitudinal zone well back from the lateral margins (Fig. 273), and the material so borne to the surface in such a zone gives rise to a moraine resembling the medial moraine formed by the union of lateral moraines, but of wholly different origin. [Illustration: +Fig.+ 273.—Diagram illustrating the same point as 272, where the structure is more complex. The bottom line of the figure represents sea level.] The phenomenon of upturning here referred to has been observed only at or near the terminus of the ice, and is perhaps due in most part to the resistance of frozen morainic or other material beneath and in front of the edge. To this should probably be added the effect of the increased rigidity of the ice at its borders, due to the low external temperature during the larger part of the year, while the interior, with its higher temperature, remains more fluent. But even this probably leaves the explanation inadequate. In not a few instances the upturning is associated with a notable _thickening_ of the layers toward their edges (Fig. 274). This suggests that perhaps there is an exceptional growth of the granular crystals of the ice near the edge of the layers, owing to the penetration of the surface-waters which are much more abundant at the borders than elsewhere, and which in the arctic glaciers probably do not penetrate deeply before they reach a freezing temperature.