A Voyage round the World / A book for boys

by William Henry Giles Kingston

“Men possessed of far more scientific knowledge than I can boast of, have been puzzled to reply to that question,” returned the captain. “The trade-winds, the diurnal motion of the earth, the expansion of water by heat, may all combine to force it along and direct its course; and yet there may be some still more potent cause at work unperceived by us, perhaps undiscoverable. One thing we know, that it was the will of the Almighty that so it should flow, for a great and beneficent object; and that, to effect it, he has employed some potent and sufficient agent, which, when he thinks fit, he will allow to be revealed to us by the light of that science which he has given as one of his best gifts to man. There are, as you perceive on the charts, other currents in the vast ocean, all set in movement for the sake of benefiting the inhabitants of the globe. While the warm Gulf Stream runs up to Spitzbergen, the Hudson’s Bay and Arctic currents bring cold water and icebergs towards the south; and a current from the North Atlantic carries its cooling waters round the arid shores of western Africa. There is the great equatorial current from east to west round the world, and numerous other currents in the Pacific and Indian Oceans, the influence of which we shall feel during our voyage; and by knowing where to search for them, and where to avoid them, we can generally make them serviceable to our object. What I would especially point out to you, my lads, is the beautiful adaptation of all the works of the Creator to the great object of the whole. The air and water are kept in motion for the benefit of man and all living beings. Order everywhere reigns supreme. Science shows us that storms are regulated by exact laws, and it is only through our ignorance and blindness that we cannot tell whence they come, and whither they go. What an admirable system of compensation exists throughout the universe! Heat, lost by radiation, is quickly restored; water, lifted up by evaporation, has its place supplied by colder currents; mighty rivers discharge their waters in vast quantities into the ocean, and from the far-off regions of the tropics the winds come loaded with dense vapours, which, precipitated at their sources with ample and regular measure, supply all their demands. I might produce numberless examples. As an instance, the whole volume of the waters of the Mississippi, rushing out at its mouth, find their way back again in an ever-constant circle to its sources among the far-off lakes of North America. The Gulf Stream fertilises the earth for the benefit of man, and it likewise carries food to regions frequented by the mighty whales. Frequently large shoals of sea-nettles, on which the black whale feeds, have been met with, borne onward towards its haunts in the north. The whale itself, it is believed, could not exist in the warm waters of the stream. Fish, also, are not generally found in it; and those which inhabit it are of a very inferior flavour. Instead, therefore, of wandering about the ocean, where they could not be procured by man, they are driven to the shallow waters near the coast, where they can easily be caught. It is a curious fact, that the warmer the water, the brighter are the colours of the fish which inhabit it; though, as food, they are generally of much less value. While the Gulf Stream largely benefits the globe, it is at the same time the proximate cause of shipwreck and disaster, from the storms which it creates, in consequence of the irregularity of its temperature, and that of the neighbouring regions, both in air and water. Perhaps nowhere is a more terrific sea found than when a heavy gale meets the Gulf Stream, when running at its maximum rate. Many a ship has gone down beneath its waters. However, I might go on all day telling you curious things about this same Gulf Stream. One thing more I will mention: people often complain of the dampness of England. The same cause which so favourably tempers the cold of our country, creates the dampness complained of. It is not that our soil is more humid, that marshes exist, or that the country is not well drained; but it is that the westerly and north-westerly breezes which prevail, come loaded with the warm vapours ascending from the tropic heated waters of the Gulf Stream.”

“Thank you, father, for all you have told us,” said Gerard; “I think I have learned a great deal I did not know before.”

I was certain that I had, and directly afterwards put down, as well as I could remember, all Captain Frankland had said. The next day we sighted Saint Vincent, one of the ten islands which form the Cape de Verd group, so-called from being off the Cape de Verds, on the coast of Africa. The islands belong to the Portuguese. They produce all sorts of tropical fruits and vegetables, so that ships often touch here to be supplied with them. A large number of the inhabitants are black, or of a very dark hue. Instead of standing directly for the Brazils, Captain Frankland shaped a course almost across the Atlantic for the coast of South America. He did this, he explained to Gerard and me, to get the wind, which generally blows off that coast when the north-east trade failed us; and to avoid the equatorial calms, in which, away from the land, vessels are often baffled for days together. I found, after I had been some time at sea, “That the longest way round is often the shortest way there,” as the saying is. In tropical latitudes, winds from different quarters blow with great regularity in different places at certain seasons of the year. The great object of a master is, to find where the wind is blowing which will be fair for him. The two most regular winds are the north-east and south-east trade-winds which blow from either side of the equator, and meet in a wide belt of calms found under it. There are currents in the air as well as in the ocean; and Silas told me that he has more than once passed ships at sea right before the wind—steering north, for instance, while his ship, with an equally fair breeze, has been standing to the south. Formerly, ships used to be steered as far south as they could get before the trade-winds; and then often found themselves baffled for days, if not weeks together, in the calm latitudes off the coast of Africa, when, if they had stood boldly across the ocean, as we were now doing, they would never have wanted a wind move or less fair. Thus it will be seen that in navigation there are currents in the sea and currents in the air to be considered, and that it requires a great deal of forethought, and knowledge, and experience, to take a ship in safety and with speed round the world. We were bowling along in grand style before the north-east trade-wind, when Gerard stopped his father in his morning walk on deck.

“I say, father, can you tell Harry and me all about this trade-wind, which we have got hold of it seems?” said he with a grave look, as if he wished to become very learned.

“Which has got hold of us rather, I should say, by the way it is carrying us along,” answered the captain, smiling. No one knew Jerry so well as he did, though he often pretended not to understand at what he was driving. “You ask a question to which it is rather difficult to reply in a brief way. Take a piece of paper; draw a circle on it; now, draw three parallel belts across it—one in the centre, and one on each side of the centre. Write on the centre belt, ‘Equatorial Calms;’ on the upper, ‘Calms of Cancer;’ on the lower, ‘Calms of Capricorn.’ The circle represents the globe; the ends of a line drawn at right angles to the belts where it reaches the circle, mark the poles. The globe moves from west to east. Now, suppose a mass of air sent off from the north pole towards the equator in a straight line, it not partaking of the diurnal motion of the earth would appear as if it came from the north-east. Another mass starting from the equator towards the pole in consequence of the impetus given it, would be going faster towards the east than the earth, and would, consequently, appear as if it came from the south-west. This actually takes place, but in the upper regions of the air. The same exchange takes place between the south pole and the equator. Now, let us see what becomes of these masses. That which started from the north pole meets in the air at about the parallel of 30 degrees; the mass which started from the equator meeting with equal force, they balance each other, and produce a calm and an accumulation of atmosphere pressing downward, and ejecting from below two surface-currents—one towards the equator, which are the north-east trade-winds; the other towards the pole, called the south-west passage-winds. This moving mass of air, which constitutes the north-east trade-wind, meets near the equator with another mass which has been moving on as the south-east trade—meeting with equal force, they form a calm; and then, warmed by the heat of the sun, they ascend, one-half streaming off high up towards the south-east—that is, counter to the surface-current—till it reaches the southern calm belt; another mass coming from the south-west, where it descends, and rushes as a north-west surface-wind towards the south pole. We have traced the mass which started from the north pole. Reaching the southern regions, it is whirled round till, at the pole itself, a perfect calm is produced, when it ascends and starts off as an upper current towards the equator; but meeting another current near the tropic of Capricorn, then descends, one-half flowing out at the surface, as I have before described, as the south-east trade, the other towards the south pole. This is the most beautiful and regular system of atmospheric circulation kept up around our globe. It has not been ascertained exactly why the masses I have spoken of take certain directions, but we know the directions they do take. The red dust we found off the Cape de Verds assists us in certain degrees. We know some of the agents—the diurnal motion of the earth, and the sun’s heating rays. There are certain counteracting or disturbing causes from which the surface-winds deviate from the courses I have described. Some lands are covered with forests, others with marshes, others with sand. All these may be disturbing causes—so are lofty mountains. From these causes, and the more powerful effect of the sun’s rays in one place than in another, hurricanes and typhoons occur, and the monsoons are made to blow—the harmattan on the west coast of Africa; the simoon, with its deadly breath, in Arabia; the oppressive sirocco in the Mediterranean. What I have said will explain that beautiful passage in Ecclesiastes, 1st chapter, 6th verse, which shows the exactness of the sacred writers whenever they do introduce scientific subjects: ‘The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits.’ Who gave Solomon this information? I doubt if any of his sages possessed that scientific knowledge which has only been attained by philosophers of late years. Perhaps I may still more clearly explain to you the cause of the circulation of the atmosphere. I told you that there were two agents at work—diurnal motion, and the heat of the sun; but to these may be added the cold of the poles, which contracts the air. Suppose the globe at rest, and covered with one uniform stagnant mass of atmosphere; suddenly heat, cold, and the diurnal motion commence their operations. The air about the equator would expand, that about the poles contract. Thus two systems of winds would commence to blow—one above, from the equator towards the poles; and as thus a vacuum would be left below, a current would come from the poles to supply its place. The diurnal motion prevents these currents running in straight lines. That coming from the poles will appear to have easting in them, and those going towards the poles westing. Not only, however, is the level of the atmosphere changed by the heating rays of the sun, but its specific gravity. Thus the heated current moves more easily and rapidly than the colder; and the latter, consequently, turns back a portion of what was going towards the poles, and adjusts the equilibrium of the atmosphere. I have already shown you the great importance of the circulation of the air in the economy of nature; and how, among the many offices of the atmosphere, it distributes moisture over the surface of the earth, making the barren places fruitful, and tempering the climates of different latitudes, fitting them as the abode of civilised man. But I will not pursue the subject further just now. You must do that for yourselves. Try and remember what I have said, and think about it whenever you have an opportunity.” Jerry and I thanked the captain for what he had told us, and I, as before, at once dotted it down as well as I could in my note-book.

Crossing the Atlantic, we sighted a glittering white rock rising fifty feet out of the water. It was, I found, the Island of Saint Paul’s. It had a curious appearance, standing thus alone in the ocean 500 miles from the coast of America, and 350 from the Island of Fernando Noronha—the snowy pinnacle of a submarine mountain. We hove-to close to it, and a boat being lowered, Mr McRitchie, Mr Brand, Jerry, and I, went on shore. The whole rock is not three-quarters of a mile in circumference. Its white colour, we found, was produced by a thin coating of a substance formed by the washing off of the birds’ dung, collected there in a succession of ages. The rock was covered with birds—my old friends, the booby and the noddy, I had so often read about. They stared at us with a stupid look as we pulled up, not at all able to make us out, and in no way disposed to make way for us. Gerard and I were for knocking as many as we could on the head; but Cousin Silas would not allow us, observing that we did not want them for food, and that they had a far better right to the rock than we had. The booby, Mr McRitchie told us, is a species of gannet, and the noddy a species of tern. The first lays her eggs on the bare rock, but the latter constructs a nest with sea-weed. While the doctor was eagerly hunting about for specimens of natural history, we were amused by watching the proceedings of some of the few inhabitants of the rock. By the side of several of the noddies’ nests we saw a dead flying-fish, evidently deposited there by the male bird. Whenever we succeeded in driving away any one of the females, instantly a big crab, which seemed to have been watching his opportunity from the crevices of the rocks, would rush out, and with greedy claws carry off the prey. One fellow, still more hungry, ran away with one of the young birds. Another was going to make a similar attempt.

“I ought to stop that fellow, at all events!” said Jerry, giving Master Crab a stunning blow. We tied his claws, and presented him as a trophy to the doctor.

“A fine specimen of Graspus” cried our scientific friend, stowing him away in his wallet.

“A capital name!” said Jerry. “He seemed ready enough to grasp anything he could lay his claws on.”

The doctor said he could find neither a plant nor a lichen on the island, and only a few insects and spiders, besides the boobies and noddies. I ought to have mentioned that we did not fail to meet with the moist and oppressive weather found under the belt of calms under the equator. Frequently I felt as if I could scarcely breathe, and nearly everybody was in low spirits and ready to grumble. Jerry and I vowed that the air was abominable. Cousin Silas stopped us.