The Hydrographic Bureau at Washington, which is in many ways useful in transatlantic navigation, issues a series of charts of an area of ocean reaching eastward from Newfoundland. There are twelve of them, one for each month of the year, and they differ only in certain pencillings which vary from month to month. Let us examine the set issued for a recent year. In the chart for January five little pyramids are clustered together in the sea, with a sixth to the north of them; in February the pyramidal little figures can be counted by the score, surrounded by zig-zag lines—they look like an encampment; in March the zig-zag lines have disappeared, and the tents, so to speak, are more scattered; in April they are much the same as in March, but in May they have increased enormously and can be counted by the hundred, reaching from the far north to over a hundred miles southward of the Grand Banks. In June they are fewer, and in July fewer still. In August only about twenty are visible; in September not more than ten; in October two, in November one, and in December two. The zig-zag lines disappear earlier than the pyramids; the former represent field-ice, the latter ice-bergs; and thus it is seen that during one year there was not a single month in which the transatlantic route was entirely free from danger from those sources. In 1882 the bergs appeared in February and disappeared in August; February, March, and April are the months for their appearance, and they often linger till October or November.
[Illustration: At Close Quarters, Among the Icebergs.]
Field-ice has its source in the Arctic basin and along the coasts of Labrador and Newfoundland, and is carried south either by the current from the Arctic or that from East Greenland. Fully eighty per cent. of the bergs have their origin in West Greenland, and most of them are fragments of glaciers, broken off in a process known as “calving,” as the glaciers slide into the deep water along-shore. Thousands are thus set adrift each year, and once adrift they begin their journey southward. Only a small proportion of the whole number ever reach the track of the steamers; some ground in the Arctic basin and break up in the frigid zone, to which they properly belong; they are very fragile, and the concussion of a gunshot is occasionally sufficient to shatter them; some are borne across from Greenland to Labrador, and lodge there until they dissolve, or crumble to pieces with the noise of thunder. The journey of those that escape disintegration in the north is slow. If they drifted directly south and met with no obstructions, they would be four or five months in reaching the transatlantic routes; and being liberated in July and August they would consequently beset the path of the steamers in December and January. Few of them, however, are not delayed, and most of them have been adrift at least a year from the time of “calving” before they arrive south enough to trouble the steamers. Some are several years in making the journey; they are held for a season in a shallow; locked up during the Arctic winter; released with the return of summer; caught again for another winter, and when once again liberated, retarded in their southward course by the necessity of ploughing through the field-ice before them. Not only are there wide variations in the date of the appearance and disappearance of the bergs in the transatlantic routes from year to year, but in different years they reach a different southern limit. It is this variability which causes mischief. If their movements were always the same, it would be easy for the captain to choose a course which would avoid them, but a course which may be entirely safe one year is often beset the next season by large quantities of ice, both in the forms of bergs and of field-ice.