The Ocean and Its Wonders

by R. M. Ballantyne

Of course, the effect of these changes is to produce north winds in one latitude and south winds in another, according to the particular wind (equatorial or polar) that happens to be in contact with the earth. At the points where these two currents cross, in changing places, we necessarily have calms, or conflicting and variable winds.

Here, then, we have the first of the constant disturbing causes, and of apparent irregularities, in the winds. The Earth, as every one knows, whirls rapidly on its axis from west to east. At the equator the whirl is so rapid that the atmosphere does not at once follow the Earth’s motion. It lags behind, and thus induces an easterly tendency to the winds, so that a north wind becomes a north-east, and a south wind a south-east. Here we have another constant cause of variation from the northerly and southerly flow. We thus account for an easterly tendency to the winds, but whence their westerly flow? It is simply explained thus:

The motion of the Earth is greatest at the equator. It diminishes gradually towards the poles, where there is no motion at all. The atmosphere partakes of the Earth’s motion when in contact with it; and when thrown upwards by heat, as at the equator, it keeps up the motion for some time, as it meets with no resistance there. Bearing this in mind, let us now follow a gush of warm atmosphere from the equator. It rushes up, and, turning north and south, seeks the poles. We follow the northern division. When it left the Earth it had acquired a very strong motion towards the east,—not so great as that of the Earth itself, but great enough to be equivalent to a furious gale from west to east. If we suppose this air to redescend whence it rose, it would, on reaching the equator, find the Earth going too fast for it. It would lag a little, and become a gentle easterly breeze. But now, throw aside this supposition;—our breeze rushes north; at latitude 30 degrees it has got cooled, and swoops down upon the Earth; but the Earth at this latitude is moving much slower than at the equator; the wind, however, has lost little or none of its easterly velocity. On reaching the Earth it rushes east much faster than the Earth itself, and thus becomes a westerly gale.

There are, however, many other agents at work, which modify and disturb what we may call the legitimate flow of the wind; and these agents are diverse in different places, so that the atmosphere is turned out of a straight course, and is caused to deflect, to halt, and to turn round: sometimes sweeping low as if in haste; at other times pausing, as if in uncertainty; and often whirling round, as if in mad confusion. To the observer, who sees only the partial effects around his own person, all this commotion seems but the disorderly action of blind chance; but to the eye of Him who sees the end from the beginning, we may certainly conclude that naught is seen but order and perfect harmony. And to the eye of Science there now begins to appear, in what was formerly an atmospheric chaos, an evidence of design and system, which is not, indeed, absolutely clear, but which is nevertheless abundantly perceptible to minds that cannot hope in this life to see otherwise than “through a glass, darkly.”

The causes which modify the action of the winds are, as we have said, various. Local causes produce local currents. A clear sky in one region allows the sun’s rays to pour upon, let us say, the ocean, producing great heat; the result of which is evaporation. Aqueous vapour is very light, therefore it rises; and in doing so the aqueous particles carry the air up with them, and the wind necessarily rushes in below to supply its place. The falling of heavy rain, in certain conditions of the atmosphere, has the effect of raising wind. Electricity has also, in all probability, something to do with the creation of motion in the atmosphere. Now, as these are all local causes, they produce local—or what, in regard to the whole atmosphere, may be termed irregular—effects. And as these causes or agents are in ceaseless operation at all times, so their disturbing influence is endless; and hence the apparent irregularity in the winds.

But these causes are themselves, not less than their results, dependent on other causes or laws, the workings of which are steady and unvarying; and the little irregularities that appear to us in the form of fluctuating and changing winds and calms may be compared to the varying ripples and shifting eddies of a river, whose surface is affected by the comparatively trifling influences of wind, rain, and drought, but whose grand onward course is never for a single moment interrupted.

Among these disturbing influences, the Gulf Stream is a very important one. It is constantly sending up large volumes of steam, which, rising into the air, induce a flow of wind from both sides towards its centre. And many of the storms that arise in other parts of the Atlantic make for this stream, and follow its course.

So much has been ascertained by scientific investigation of the winds, that we can now distinctly map out the great belts or currents which pass right round the world. We can tell in which parallels winds with easting, and in which those with westing, in them, will be most frequently found; and by directing our course to such places, we can to a certain extent count upon profiting by the winds that will be most suitable. Before the facts of atmospheric circulation were known, mariners sailed by chance. If they happened to get into the belt of wind that suited them, their voyages were favourable; if they got into the wrong region, their voyages were unfavourable,—that was all. But they had no idea that there was any possibility of turning the tables, and, by a careful investigation of the works of the Creator, coming at last to such knowledge as would enable them to reduce winds and waves, in a great degree, to a state of slavery, instead of themselves being at their mercy.

The world may be said to be encircled by a succession of belts of wind, which blow not always in the same direction, but almost invariably with the same routine of variations. A vessel sailing from north to south encounters these belts in succession. To mariners of old, these varying winds seemed to blow in utter confusion. To men of the present time, their varied action is counted on with some degree of certainty. The reason why men were so long in discovering the nature of atmospheric circulation was, that they were not sufficiently alive to the immense value of united effort. They learned wisdom chiefly from personal experience—each man for himself; and in the great majority of cases, stores of knowledge, that would have been of the utmost importance to mankind, were buried with the individuals who had laid them up. Moreover, the life of an individual was too short, and his experience too limited, to enable him to discover any of the grand laws of Nature; and as there was no gathering together of information from all quarters, and all sorts of men, and all seasons (as there is now), the knowledge acquired by individuals was almost always lost to the world. Thus men were ever learning, but never arriving at a knowledge of the truth.

May we not here remark, that this evil was owing to another evil—namely, man’s ignorance of, or indifference to, the duty of what we may term human communication? As surely as gravitation is an appointed law of God, so surely is it an appointed duty that men shall communicate their individual knowledge to each other, in order that the general knowledge of the species may advance and just in proportion to the fidelity with which men obey this duty—the care and ability with which they collate and systematise and investigate their knowledge—will be the result of their efforts.