Page:A Voyage of Discovery and Research in the Southern and Antarctic Regions Vol 1.djvu/261

1841 was blackened with Indian ink: it rose from 33° to 40°.2, the sun's altitude being at the time only four degrees. Heavy clouds were soon afterwards observed rising both at east and north-west: those in the latter direction were of a peculiarly threatening appearance, with hard rugged outlines, like the cumulus clouds of the equatorial regions, with bright reflections of light from their more prominent points, affording a strong contrast to the extreme darkness of the frowning mass. The setting sun was also a very remarkable object, being streaked across by five dark horizontal bands, of nearly equal breadth, and flattened into a most irregular form by the greater refraction of its lower limb as it touched the horizon, at 11^h 56^m 51^s; skimming along to the eastward, it almost imperceptibly descended until its upper limb disappeared exactly seventeen minutes and thirty seconds afterwards. The difference of the atmospheric refraction at the upper and lower limb of the sun was carefully determined by several measurements of the horizontal and vertical diameter, and found to amount to 5′ 21″, the horizontal diameter being 32′ 31″, and the vertical diameter only 27′ 10″, that given in the Nautical Almanac being 32′ 34″; thus showing also that the flattened appearance of the sun was not produced in the least degree by the elongation of the horizontal diameter, as some have supposed. We also remarked the peculiar purple colour that the vapour of very low altitudes exactly opposite to the setting sun reflects so constantly in