Ice is another major hazard to sailors venturing far below 40° south. Although the ice limit dips south around Cape Horn, icebergs are a significant hazard for vessels in the area. In the South Pacific in February (summer in Southern Hemisphere), icebergs are generally confined to below 50° south; but in August [winter] the iceberg hazard can extend north of 40° south. Even in February, the Horn is well below the latitude of the iceberg limit. Some icebergs reported by ‘Horners’ were immense; 150 miles long and as much as 1500 feet high. Such an iceberg would be comparable to meeting a frozen version of Wales cut loose from the mainland and adrift in the Southern Atlantic. These gigantic icebergs were the nemesis of many vessels which unwittingly became ‘embayed’ by sailing into a concavity in the ice either without realising it because of the immensity of scale, or lured there thinking there was a way through, or forced there through adverse winds. Fluky winds caused by the iceberg itself or a change in wind direction then often meant a ship found it impossible to sail out of the bay in the iceberg and led to the vessel's inevitable and slow destruction. There are a number of accounts of passing ships fortunate enough not to be so entrapped witnessing vessels going to their certain destruction with descriptions of the piteous cries that could be heard from crews and passengers aboard to whom it was impossible to lend assistance other than their prayers. Much good they did them!
The prevailing west to east wind combined with the Antarctic Circumpolar Current, sometimes known as the West Wind Drift which also flows west to east, create particular problems for vessels attempting to round the Horn the ‘wrong’ way, i.e. from east to west. Although this affects all vessels to some extent, it was a particularly serious problem for square-rigged sailing ships, which could make very little headway against the wind at the best of times, and the best of times were rarely those round Cape Stiff. So little headway was made westwards on occasions that it was by no means uncommon for a ship to turn tail and sail right round the globe in an easterly direction in order to reach her destination, which is what Captain Bligh did in the Bounty. However, "right round the globe" along 50° south is not equivalent to the circumference of the globe, as it is not a great circle.
The chart at right gives some idea of the problem facing the captains of ships in general and the captain of the Edward Sewall in particular when rounding the Horn. In 1914 it took the Edward Sewall 67 days of hard sailing to deny Davy Jones, who had had her sister ship, the Arthur Sewall in 1908, lost with all hands off the Horn. The destination of the Arthur Sewall was Seattle which accounts for some of the specific difficulties represented on the chart; e.g. around day 22 the wind must have veered northwards forcing the captain to run south then east. Had his destination been New Zealand or Australia he could probably have cleared the Horn sooner either continuing on the starboard tack from day 19 or doing so in the ensuing three or four days. What is not clear from the plotted positions is whether there was some other reason preventing him going further south or west such as ice. Rounding the Horn was a lottery; given a sound ship, sober captain, competent crew and good seamanship, the outcome depended on the direction and strength of wind predicated by the ship's intended destination.
An even more extreme example of a ship held up by head winds was the Garthneill, which left Melbourne for Bunbury [about 100 miles south of Perth] intending to load railway sleepers for Cape Town. This should have been a simple coasting trip of about 2000 miles westwards along the southern coast of Australia but was made impossible by strong prevailing westerly winds. The ship was eventually forced to run before the wind and go right around the world eastwards via Cape Horn and the Cape of Good Hope and arrived at Bunbury from the West having taken only 9 days longer than the Edward Sewall took to weather Cape Horn.
What lay at the heart of the problem was the inability of square rigged ships to sail to windward. Consider the Edward Sewall; she needed to continue north on day 22 but the wind shifted to blow from the north. What progress could be made? In theory, the answer was about 30-35 miles in any one day north of the ship's starting point if she was lucky and the wind was not so strong as to compel the captain, as seems to have been the case with the Edward Sewall to reduce all canvas - even down to bare poles - and run before a severe storm. An average ship could steer no closer than about 65° to the wind. Beating to windward meant tacking across the wind repeatedly in a zig-zag to make any slight headway, all of which required sea room - feasible on day 22, impossible on day 33. Violent wind or large waves often made even this impossible, with no alternative but running before the storm as may have been the case with the Edward Sewall on day 22. In addition, leeway, the effective sideways thrust that the wind exerted on the ships hull and rigging, would have pushed a vessel a further 5° or more off her intended course.
Another consideration for the skipper in the days before weather forecasts and after a prolonged delay trying to round the Horn would have been the state of the crew and the ship, what provisions were on board, and the health and well being of any cargo or passengers. Having to revictual at the Falklands or east coast of South America would have been an extra cost, whereas turning about and running round the 50th parallel eastwards when down to the last say two months provisions might have been tedious but was at least had a more-or-less certain outcome.
It is worth noting that to continue sailing along the 50th parallel you would completely miss both New Zealand and Australia, passing to the south of both and sight no land till approaching Cape Horn again! Note also in the above chart the sea room required by the Edward Sewall compared either with that available in the Magellan Straight [which is anything but! and is the opening by Cape Virgins which I'm sure should be called something different] or with the Beagle Channel, which is more or less obscured on the above chart by the 55° parallel and even more constricted than Magellan Straight.