Before the Titanic disaster the accepted mail steamers outward track between January 15 and August 14 followed the arc of a great circle between the Fastnet Light and a point in latitude 42° N. and 47° W. (sometimes termed the "turning point"), and from thence by Rhumb Line so as to pass just south of the Nantucket Shoal light vessel, and from this point on to New York. This track, usually called the outward southern track, was that followed by the Titanic on her journey.
An examination of the North Atlantic route chart shows that this track passes about 25 miles south (that is outside) of the edge of the area marked "field ice between March and July," but from 100 to 300 miles to the northward (that is inside) of the dotted line on the chart marked, "Icebergs have been seen within this line in April, May, and June."
That is to say, assuming the areas indicated to be based on the experience of many years, this track might be taken as passing clear of field ice under the usual conditions of that time of year, but well inside the area in which icebergs might be seen.
It is instructive here to remark that had the "turning point" been in longitude 45° W. and latitude 38° N., that is some 240 miles to the south-eastward, the total distance of the passage would only have been increased by about 220 miles, or some 10 hours' steaming for a 22-knot ship. This is the route which was provisionally decided on by the great trans-Atlantic companies subsequent to the Titanic disaster.
It must not be supposed that the lane routes referred to had never been changed before. Owing to the presence of ice in 1903, 1904, and 1905 from about early in April to mid-June or early in July, westward-bound vessels crossed the meridian of 47° W. in latitude 41° N., that is 60 miles further south than the then accepted track.
The publications known as "Sailing Directions," compiled by the hydrographic office at the Admiralty, indicate the caution which it is necessary to use in regions where ice is likely to be found.
The following is an extract from one of these books, named "United States Pilot (East Coast)," Part I (second edition, 1909, p. 34), referring to the ocean passages of the large trans-Atlantic mail and passenger steamers:
To these vessels one of the chief dangers in crossing the Atlantic lies in the probability of encountering masses of ice, both in the form of bergs and of extensive fields of solid compact ice, released at the breaking up of winter in the Arctic regions, and drifted down by the Labrador current across their direct route. Ice is more likely to be encountered in this route between April and August, both months inclusive, than at other times, although icebergs have been seen at all seasons northward of the parallel of 43° N., but not often so far south after August.
These icebergs are sometimes over 200 feet in height and of considerable extent. They have been seen as far south as latitude 39° N., to obtain which position they must have crossed the Gulf Stream impelled by the cold Arctic current underrunning the warm waters of the Gulf Stream. That this should happen is not to be wondered at when it is considered that the specific gravity of fresh-water ice, of which these bergs are composed, is about seven-eighths that of sea water; so that, however vast the berg may appear to the eye of the observer, he can in reality see one-eighth of its bulk, the remaining seven-eighths being submerged and subject to the deep-water currents of the ocean. The track of an iceberg is indeed directed mainly by current, so small a portion of its surface being exposed to the action of the winds that its course is but slightly retarded or deflected by moderate breezes. On the Great Bank of Newfoundland bergs are often observed to be moving south or southeast; those that drift westward of Cape Race usually pass between Green and St. Pierre Banks.
The route chart of the North Atlantic, No. 2058, shows the limits within which both field ice and icebergs may be met with, and where it should be carefully looked out for at all times, but especially during the spring and summer seasons. From this chart it would appear that whilst the southern and eastern limits of field ice are about latitude 42° N., and longitude 45° W., icebergs may be met with much farther from Newfoundland; in April, May, and June they have been seen as far South as latitude 39° N. and as far east as longitude 38° 30´ W."