The visitor strolling along the shingly bays of Cornwall, kicking the drift weeds as they lie in a long black line upon the shore, now and then chances upon a worn and shattered piece of bamboo, or upon the bright seeds of some tropical clime. If these weather-beaten travellers could tell of their long journeying ere they were finally cast ashore, his attention would be instantly arrested, for these worthless pieces of drift are the “tallies” the Almighty has placed upon the ocean, which prove that what we term the great waste of waters, circulates in their ocean depths as regularly and unerringly as the blood in our own veins.
By slow degrees the great maritime nations of the earth are building up a new science —the physical geography of the sea. We are discovering the laws which cause and regulate those once mysterious currents which seemed to be urging the ancient mariner who ventured into unknown seas, towards the dreadful verge of the world.
Of these currents we are most fully acquainted with that known as the “Gulf Stream” of the Atlantic. The traffic between ourselves and America has become so great, that if every keel could plough an enduring mark upon the “herring-pond,” there would perhaps be scarcely a part left on its vast surface between the latitudes of 20° and 45° unmarked. This sea being thus brought within the vision of countless eyes trained to watch the changes of the deep, it is not surprising that we should have ascertained its circulating system with tolerable accuracy.
Yet no further back than the time of Franklin, we were in entire ignorance of the Gulf Stream, and of its effects upon navigation. Vessels bound for New York in the winter were astonished to find themselves one day sailing along a summer sea, and the next day, when within sight of land perhaps, blown off the shore by an Arctic gale, which dressed in icicles the spars and ropes. By degrees, however, it came to be understood that there was a constant set of the ocean into the Gulf of Mexico from the south-east and north, and a flow outwards towards the north-east. Since the year 1808, the direction of these currents has by degrees been most carefully mapped by the practice introduced into our navy of casting bottles into the ocean, containing papers accurately marking the position of the ship at the time these fragile messengers were sent forth.
The surface drift after many days casts these ashore, if they go in a shoreward direction; and the records of the passages made by them for the last half century have been collected by the hydrographer of the Admiralty into what is termed “The Current Bottle Chart.” This singular map clearly shows that all the bottles thrown into the ocean near the Canaries, or the Cape do VerdeIslands, make directly for the west, and touch land among the West India Islands, some even penetrating to the shores of the Gulf of Mexico.
Those, again, which are cast into the ocean on the western side of the Atlantic, from about the latitude of New York, make off in a northeastern direction, and voyage until they are cast on the western shores of Europe. Frail as these bottles may seem, some of them must have made extraordinary voyages ere they finally reached their haven.
Thus, a bottle thrown overboard from the Prima Donna off Cape Coast Castle, on the west coast of Africa, after voyaging for two years, was finally found on the coast of Cornwall.
Now, it is evident that this little messenger, before it could have reached this shore, must have been carried by the Guinea current eastward until it met the African current coming from the southward, with which it would recross the equator, and travel with the equatorial current through the West India Islands until it got within the influence of the Gulf Stream, which finally carried it to the north-east, and cast it on the shores of Cornwall, after a journey of many thousand miles.
Other bottles, again, that have been east into the sea from sister ships, making for the Arctic Ocean, although at seven hundred miles distance, have been known, after traversing the Atlantic from north to south-west, to finish their journey within thirty miles of each other!
And now having shown the direction of the currents to and from the Gulf of Mexico, let us follow the Gulf Stream. If we look at a map of the Gulf of Mexico we find that it is a land-locked sea on the north, south, and west; it is shaped indeed like a vast cauldron, the ascertained average depth of which is one mile; for heating this cauldron we have the fierce sun of the equator, which sends its temperature up to eighty-five degrees. The sea-water thus heated expands, and pours out of the Gulf, in one immense stream, the centre of which is found to be about two inches higher than its edges in the surrounding ocean. This stream, which in consequence of its intense saltness is tinged a deep indigo colour, immediately it clears the Straits of Florida makes away in a north-east direction for the western shores of the Old World.
The extraordinary nature of the flow is, that it is a warm river in the ocean, its banks on either side, and its bottom, being in the winter composed of icy cold water. This tremendous issue from the Gulf must however find some supply to fill up the vacuum that otherwise would arise, and we find it mainly coming from the Arctic Sea, the current pushing its way down between the coast of North America, and the Gulf Stream flowing up across the Atlantic, in a north-east direction.
The Arctic downward current, however, expands and contracts with the seasons; at one time shouldering the hot current more to the east, and then again giving way on the coming of winter. By reason of this agency the Gulf Stream is continually waving about in mid-ocean, as Lieutenant Maury poetically says ”like a pennon in the breeze.”
But there is also the flow into the Gulf termed
the Equatorial Current, which sweeps through the West India Islands, and enters the cauldron from the eastward. Thus we have a great horse-shoe bend, as it were, in the currents of the Atlantic Ocean, in the centre of which there is a region of comparatively still water, situated midway between the Azores, the Canaries, and the Cape Verde Islands.
Here in the centre of the great whirl, the whole surface of the sea is covered with thickly matted Gulf weeds, and with all the drift wood, and other matters sloughed off by the southern edge of the Gulf Stream; this extraordinary floating surface, termed the Sargossa Sea, is the same that Columbus met with in his great voyage of discovery, and which terrified his sailors into the belief that they had reached the limits of navigation.
This singular marine phenomenon is an example on a small scale of what we may see occurring every day in a pan of water to which a rotatory motion has been given — all the light floating particles, such as bits of straw, cork, &c, collecting in the centre, and there remaining, in consequence of its being the spot least disturbed by the surrounding motion. Into this great “bend” of the Atlantic we behold the gathering place and final tomb of those mighty icebergs which, every spring, issue forth in such majestic procession from their birth-place in the Arctic Ocean, sucked southward by the current flowing towards the Gulf. When, after their long march, they reach these still waters, their dissolution rapidly commences, the warm air above, and the hot water beneath assault and undermine their glittering pinnacles, and with thundering crashes they split and subside into their ocean bed.
Lieutenant Maury in his charmingly suggestive volume, “The Physical Geography of the Sea,” has ingeniously and truly likened the grand mechanism of the Gulf Stream to the artificial methods by which we produce warmth in our houses. Messrs. Weeks, the great hot-house builders, might have taken a hint from the currents of the Atlantic as to the best method of producing a summer atmosphere in the depths of the winter.
In the downward flow of the Arctic current would be found the counterpart of the feed-pipe of the hot-water apparatus; in the Caribbean Sea and the Gulf of Mexico, the vast boiler which elevates the temperature of the water to eighty-five and sometimes ninety degrees and in the Gulf Stream, the hotwater pipes which as they floor themselves out over the ocean for thousands of miles, present a vast amount of cooling surface, which gives off to the western breeze a moist hot-house temperature in the cold seasons of the year. It must have often struck the reader as a remarkable fact that even as late as June many of the ports in our North American provinces are closed with ice, whilst we are revelling in bright summer weather — yet Labrador is situated in a more southerly parallel of latitude than England.
The explanation of this is, that the Gulf Stream is pushed off the North American seaboard by the descending cold current, the difference of temperature between the two streams running side by side being in the depth of winter not less than thirty degrees. We may here state, en passant, that the tremendous fogs, which in the winter season are always found hanging over the Grand Banks of Newfoundland, are attributable to the condensation of the warm and humid air of the edge of the Gulf Stream, by the cold air of the adjacent current.
If we follow the Gulf Stream across the ocean, we perceive how fully it fulfils the purpose for which it was designed. Sir Walter Scott tells us that the pools in the Orkneys are never frozen, the effects of the grand hot-water warming apparatus of a far distant shore being sensibly felt even in these islands, which are situated in latitude nearly ten degrees further north than the ice-bound coast of Labrador.
We all know that in Great Britain there is an extraordinary difference between the eastern and western coasts – so great indeed as to induce completely different systems of agriculture. The Emerald Isle owes her splendid grazing-land to the soft west breezes born of the Gulf Stream which strikes full upon her shores; the western shores of England are robed in bright green pastures nourished with the warmth and moisture issuing from the same tropical source.
The dairy produce of Great Britain has its root and issue in this stedfast hot-water river in the ocean, the limits of which modern science has so accurately mapped; nay, the florid plump looks of our people, and the large size of our domestic animals, are but effects of that moist and genial atmosphere which finds its birthplace in the beneficent Gulf Stream.
And in order to bring the effects of this extraordinary marine phenomenon closer home to the stomach of our reader, we may perhaps be permitted to ask him, how it is that of late years he has purchased peas, potatoes, and broccoli so many weeks before their season in Covent Garden Market?
Peas in May were once thought to be an extravagance, only allowable to a duke. Now any moderate man may indulge in them to his heart’s content. Well, these vegetables are forced — but in a hot-house atmosphere of nature’s own contriving.
Where the tail of the British dolphin dips into the Atlantic, there the effects of the Gulf Stream are most felt; it is bathed with the warm moist air, heated by the far-off Gulf cauldron, and we may say with exactness that the majority of our early vegetables sold in the open market are forced in hot-houses in Cornwall and Portugal (the seaboard of the more southerly promontory), by means of a boiler situated beyond the West Indian Archipelago, the conducting hot-water pipe of which runs for nearly four thousand miles between the cold walls of the surrounding ocean.
Had the ancients been aware of this property of the ocean, it would have modified the representations of the Pagan Olympus, and we should have been familiar with the spectacle of — Neptune turned gardener…