Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 1.djvu/151

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Chap. IV.]
GEOLOGICAL NOTICE.
77
1840

headland dividing these presents a perpendicular escarpment of basalt. Approaching Cape Cumberland, the sea breaks upon a low black rugged ledge of basalt, backed by a swampy green bog, two miles in length, and half a mile in breadth, beyond which rises a range of trap hills.

"A remarkable rock, called the 'Sentry Box,' faces the entrance to Cumberland Bay; it was not landed upon, but the succession of terraces, nearly horizontal to its summit, sufficiently indicated its basaltic structure to be the same as the main land.

"The range of mountains flanking Cumberland Bay on each side generally present the same trap terraces as in Christmas Harbour. Six miles and a half up the bay are two inlets nearly opposite to each other; the one on the south side is a mile and half deep, a mile broad at its widest part, and one-third of a mile at the entrance. The trap rocks surrounding this bay differ from the others in containing drusy cavities of beautiful quartz crystals, many fine fragments of which were scattered about the surface of the rocky ledges.

"At the top of the bay is a remarkable hill, between 300 and 400 feet in height, constituted of an igneous arenaceous slate, confusedly intermingled with greenstone and basalt, having a crater-shaped summit, filled by a lake 200 yards long, and 150 broad, three feet deep near the margin, and the centre covered with thin ice. It is surrounded by an irregular wall of greenstone, from five to twenty feet in height.