Another time, when Franklin and Beechey had approached one of these ice-walls, a huge fragment suddenly slid from its side, and fell with a crash into the sea. At first the detached mass entirely disappeared under the waters, casting up clouds of spray, but soon after it shot up again at least 100 feet above the surface, and then kept rocking several minutes to and fro. When at length the tumult subsided, the block was found to measure no less than 1500 feet in circumference; it projected 60 feet above the water, and its weight was calculated at more than 400,000 tons. Besides the glaciers of Magdalena Bay, Spitzbergen has many others that protrude their crystal walls down to the water’s edge; and yet but few icebergs, and the largest not to be compared with the productions of Baffin’s Bay, are drifted from the shores of Spitzbergen into the open sea. The reason is that the glaciers usually terminate where the sea is shallow, so that no very large mass if dislodged can float away, and they are at the same time so frequently dismembered by heavy swells that they can not attain any great size. The interior of Spitzbergen has never been explored. According to the Swedish naturalists,[8] who climbed many of the highest mountains in various parts of the coast, all the central regions of the archipelago form a level ice-plateau, interrupted only here and there by denuded rocks, projecting like islands from the crystal sea in which they are imbedded. The height of this plateau above the level of the ocean is in general from 1500 to 2000 feet, and from its frozen solitudes descend the various glaciers above described. During the summer months, the radiation of the sun at Spitzbergen is always very intense, the thermometer in some sheltered situations not seldom rising at noon to 62°, 67°, or even 73°. Even at midnight, at the very peak of the high mountain ascended by Scoresby, the power of the sun produced a temperature several degrees above the freezing-point, and occasioned the discharge of streams of water from the snow-capped summit. Hence, though even in the three warmest months the temperature of Spitzbergen does not average more that 34½°, yet in the more southern aspects, and particularly where the warmth of the sun is absorbed and radiated by black rock-walls, the mountains are not seldom bared at an elevation nearly equal to that of the snow-line of Norway, and various Alpine plants and grasses frequently flourish, not only in sheltered situations at the foot of the hills, but even to a considerable height, wherever the disintegrated rocks lodge and form a tolerably good soil.