Volume 14 Australasia - dana ward's homepage

DIUFT ICE. 27drifting northwards with the current differ both iu their form and origin. Some,which break away from steep upland valleys, present a great diversity of outlineand appearance. According to the lines of fracture or the tilt of the glaciersshooting them seawards, they rise above the surface in the form of domes, peaks,or needles. Others again, which are usually of vast size, take the shape of rectangularblocks with almost level upper surface. These are not of glacier origin,but have been detached from the icy barrier skirting the flat coastlands at varyingdistances. They do not melt even in summer. During the fine seasons of 1841,1842, and 1843, Ross found that only on eighteen days the temperature rose threeor four degrees above freezing point. Some were fringed with transjDarent stalactites,which this explorer was unable to explain, as he had never observed the icemelting.As far as can be judged from the few observations hitherto made, the frozenmasses, 160 to 180 feet high, are simply the land ice gradually impelled seawardsby the pressure of the more or less inclined masses covering the interior of thecontinent. Owing to their specific gravity thej' project for distances of even10 or 20 miles beyond the coastline, while still adhering to the rocky bed. In theneighbourhood of the barrier Ross found a depth of 250 fathoms, which is preciselythe depth at which icebergs rising 180 or 200 feet above the surface must, so tosay, " lose their footing," and float away freely. The weight of the icebergs beingabout nine-tenths of that of marine water, nine-tenths of their volume must necessarilyremain .submerged ; but the mass being generally broader at the base thanthe summit, the depth of the submerged walls must be estimated at seven or eighttimes the height of the exposed clifl's.Once detached from the continental sheet of ice by some rectilinear form ofbreakage, the huge flotsam sets out on its long journey towards the equatorial seas.Some of the blocks present a regular wall 5 or 6 miles long with arched openingsat the base. They look almost like some street frontage gone adrift, at timessparkUng in the sun, but more frequently wrapped in vapour, like some mistyphantom of the brain. A nearer view reveals a frowning stronghold, faced bymighty bastions ; embattled ramparts or gloomy recesses where the angry watersdisappear amid the flanking towers ; overhanging cornices with snowy draperiespendent from the summit. The icy cliffs, standing out at a distance with even surfaceof uniform duU colour, are now resolved into an endless variety of tints and outlines.Throughout the whole thickness of the walls follow the parallel parting lines of thesuccessive snowy layers crystallized by pressure and the weather, drawing continuallycloser with the superincumbent weight, here and there warped to serpentinecurves or else fractured with sharp fissures. The prominent parts are of a dazzlingwhiteness, others shaded in blue, each slope, each crystal aperture the loveliest azure,and at night the floating mass is all aglow with an opal phosphoi-escence. It driftsslowly with the current, incessantly lashed by the waves breaking against it, asagainst some rocky shoal. The crews of passing vessels often hear the continuousthunder of the waters rushing through its cavernous recesses and dashing againstthe inner walls. Then the sustaining pillars at last give way, the arched vaults