A second attempt at Antarctic exploration was made by Wilkes from Sidney, N. S. W., which was left December 21, 1839. A compact barrier of field ice, with frequent large bergs, was fallen in with on January 11, 1840, and from this time on the ships were often in imminent danger owing to continuous ice, impenetrable fog, bad weather, and occasional embayment of the vessels in the ice-pack. It is scarcely needful to enter into the details of Wilkes's perilous voyage from longitude 95° E. to 155° E. and in latitudes ranging from the Antarctic Circle to the neighborhood of the seventieth parallel. It may be mentioned, however, that the Peacock narrowly escaped entire destruction by collision with a heavy iceberg, which seriously injured the ship. Fortunately she cleared the berg in time to escape crushing by the falling of detached ice masses from the overhanging floe berg. Heavy gales and the bad sanitary condition of the ship caused the medical officers of the Vincennes to specially report to Wilkes that such continued exposure would so weaken the crew by sickness as to hazard the ship and the lives of all on board. Wilkes, however, had sighted the long-looked-for Antarctic land, and, disregarding the warning, followed the coast-line eastward, keeping his squadron as near it as the conditions would permit. The land was a series of lofty mountain ranges, often snow-capped, frequently broken by indentations, and, worst of all, shut out from immediate approach by an almost continuous ice-barrier, which in its extent, height, and appearance struck every beholder with admiration not unmixed with apprehension. This barrier rose perpendicularly from the deep sea to a height varying from one hundred to two hundred feet above the level of the water, which gave no bottom in soundings ranging from one hundred and fifty to two hundred and fifty fathoms. Despite this great depth of water, the perpendicular icy barrier was evidently grounded, thus indicating ice of a thickness of about one thousand feet. [Illustration: The Ice-Barrier. (From a sketch by Captain Wilkes.)]