But these interesting phenomena have not hitherto been subject to systematic observation, and our knowledge of them is therefore uncertain. Numerous glacial marks, however, such as polished striated rocks, moraines, erratic blocks, &c., prove that the whole of Greenland, even the small islands and skerries outside the coast, has once been covered by the inland ice. Numerous raised beaches and terraces, containing shells of marine mollusca, &c., occur along the whole coast of Greenland, and indicate that the whole of this large island has been raised, or the sea has sunk, in post-glacial times, after the inland ice covered its now ice-bare outskirts. In the north along the shores of Smith Sound these traces of the gradual upheaval of the land, or sinking of the sea, are very marked; but they are also very distinct in the south, although not found so high above sea-level, which seems to show that the upheaval has been greater in the north. In Uvkusigsat Fjord (72 deg. 20' N.) the highest terrace is 480 ft. above the sea.[23] On Manitsok (65 deg. 30' N.) the highest raised beach was 360 ft. above the sea.[24] In the Isortok Fjord (67 deg. 11' N.) the highest raised beach is 380 ft. above sea-level.[25] In the Ameralik Fjord (64 deg. 14' N.) the highest marine terrace is about 340 ft. above sea-level, and at Ilivertalik (63 deg. 14' N.), north of Fiskernaes, the highest terrace is about 325 ft. above the sea. At Kakarsuak, near the Bjornesund (62 deg. 50' N.), a terrace is found at 615 ft. above the sea, but it is doubtful whether this is of marine origin.[26] In the Julianehaab district, between 60 deg. and 61 deg. N., the highest marine terraces are found at about 160 ft. above the sea.[27] The highest marine terrace observed in Scoresby Fjord, on the east coast, was 240 ft. above sea-level.[28] There is a common belief that during quite recent times the west and south-west coast, within the Danish possessions, has been sinking. Although there are many indications which may make this probable, none of them can be said to be quite decisive.[29] [_Geology._--So far as made out, the structure of explored Greenland is as follows: