The above words had not been long written, when papers told us of the awful hurricane of September, 1900, in U.S. Texas. A deep cyclone passed over the devoted town of Galveston, the direction of the wind suddenly changing as the centre of the cyclone went by: and the heaped-up waters from either side coming together poured their united volume over the land.
That was a flood which “turned the city into a raging sea.” Buildings were levelled; houses fell like packs of cards; vessels were carried miles inland; men and women and children perished by thousands. When the lessening wind allowed the waters to retire, an inch-deep layer of slime was found over everything.
Such facts as these help to show how vast is the power of moving air over the ocean.
As a strong wind blows, the upper layer of water slips along in obedience to its push; and fresh lower surfaces are bared to the same influence. Also, the movement of the upper layer tends to drag on the layer just below, which again affects the one lower still. By influence thus exerted and passed from one to another, the result of a long-continued wind-pressure in one direction is to set going powerful streams, which in the first instance were due chiefly or only to wind.
Round the Earth, where fairly open sea permits them to develop, are two wide belts of very persistent winds—the Trades—which remain practically the same all the year round; only shifting their limits with the changing seasons.
They blow from the north-east and from the south-east slanting towards the equator. So, speaking roughly, they are easterly winds travelling towards the west. As a consequence of their steady pressure, we have the great Equatorial Current of the tropics, pouring from east to west in two halves, north and south of the equator. This vast ocean-river, started and kept going by the trade-winds, has been described in the more important part of its course as a “magnificent surface-current of hot water, four thousand miles long by four hundred and fifty broad,” moving “at an average rate of thirty miles a day”—and, it may be added, at least over six hundred feet in depth.
Between the Trade-wind belts is a belt of dead calms, known to sailors as “The Doldrums.” This belt divides in two the Equatorial Current; and in it is found the inevitable “Counter Current,” mentioned earlier, flowing from west to east.
Another belt of steadfast winds is that of the “Roaring Forties,” in the Southern Ocean; a wide stretch of all but landless sea, between 40° and 50° south latitude. These “Brave West Winds,” as they are called, being again the reverse of the easterly Trades, blow all the year round, and nearly all the world round, since only the southern extremity of South America interferes with them.
They too give birth to a powerful current, flowing from west to east; and this mighty stream, almost encircling the Earth, has a mission to fulfil.
Already it has been said that each lesser ocean in the world has its own separate circulation-system. This southern stream, with the Roaring Forties for its parent, has for its especial task to unite all those smaller systems into one. It has to refuse to the minor oceans a lonely and self-absorbed policy, and to insist on the great truth of a world-wide Ocean unity. It has to carry gifts from the Pacific to the Atlantic, from the Atlantic to the Indian, from the Indian to the Pacific again. It has to despatch streams northward into more distant regions, with messages of goodwill to all.