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"oce Anic CURRENTs. 225
rent moves along northward, it retains a large proportion of the warmth which it had in the Gulf, and is easily recognized from the rest of the ocean by its higher temperature, even as far north as the banks of Newfoundland, where the temperature is from 8° to 10° above the surrounding ocean. To the east of Boston and in the meridian of Halifax, the stream is two hundred and seventy-six miles broad. Here it is suddenly turned to the east, its western margin touching the extremity of the great bank of Newfoundland, where the current sends off a branch which proceeds to the north-east, sometimes depositing tropical fruits and seeds upon the coast of Norway, and the shores of Ireland and the Hebrides. The main current continues to flow and spread out until, in the neighborhood of the Azores, it is about five hundred miles in breadth. From the Azores it flows towards the straits of Gibraltar, the island of Madeira, and the Canary isles, along the western shores of Africa as far south as Cape Verd, where it is again deflected by meeting the great equatorial current flowing from the coast of Guinea to the Brazils. In this manner, according to Humboldt, the waters of the Atlantic are carried around in a continual whirlpool, performing a circuit of 13,000 miles in about two years and ten months. The branch of the Gulf Stream which is given off near the banks of Newfoundland, passes northward and eastward by the coast of Scotland and Norway, as far as the North Cape, where, being met by a polar current from Nova Zembla, it is deflected westward along both sides of Spitzbergen ; still influenced by the polar current, it passes along the shores of Greenland to Davis’ Straits, where it meets a fourth current from Baffins Bay, which deflects it southward towards the banks of Newfoundland, where it again meets the Gulf Stream. Thus two great whirlpools, connected with each other and revolving in opposite directions, touch at the Banks of Newfoundland, which seems to be a bar cast up by their conflicting waters. Branches of the Gulf Stream sent off at the Azores, set from the Bay of Biscay through the English Channel, and through St. George's Channel. The general direction of these great currents may be observed on the little chart preceding. Besides these great currents, there are local or temporary currents, produced by winds, the discharge of rivers, the melting of ice, &c. The great oceanic currents however depend upon no temporary or accidental circumstances, but like the tides, on the laws which regulate the motions of the heavenly bodies. The lines of coast which are subjected to their continual action, are undergoing perpetual change, the amount of this change being dependant upon the exposure, and the actual constitution of the coast. We find everywhere, the most lofty cliffs, promontories, and precipices, whatever be their composition, whether like the primary deposits of the Shetland isles, or like the chalk cliffs of Dover, or the diluvium of Boston Harbor, all in a state of rapid and fearful destruction, crumbling away more or less quickly according to the hardness and crystalline character of the materials which compose them. The whole of Boston Harbor, which is now dotted with small islands, was once one piece of solid land. The diluvium which formerly covered the rocks, has been gradually worn away by the ocean, the outermost islands present nothing but the bare rock, and the inner ones are now being denuded. Indeed, as Prof. Hitchcock observes, when writing of the effect of the ocean upon coasts exposed to its fury, “It is difficult to examine the coast of Nova Scotia and New England, to witness the great amount of naked battered rocks, and to see harbors and indentations, chiefly where the rocks are rather soft, while the capes and islands are chiefly of the hardest varieties, without being convinced that most of the harbors and bays, have been produced by this agency.” To witness in perfection the immense power of the waves, urged by the tempests and currents upon the coasts exposed to their irresistable force, we must visit the northern isles of Scotland, and behold steep cliffs hollowed out into deep caves and lofty arches; and immense blocks of stone overturned and carried incredible distances. In the winter of 1802, in the isle of Stenness, says Dr. Hibbert, a tabular shaped mass of rock, eight feet two inches, by seven feet, and five feet one inch thick, was dislodged from its bed and removed to a distance of from eighty to ninety feet; and on Meikle Roe, one of the Shetland isles, a mass of rock twelve feet square, and five
ER CRG.ACHMENT'S OF THE SEA. 227
feet in thickness, was removed from its bed fifty years ago, to a distance of thirty feet, and has since been twice turned over. The long continued and violent action of the surf, finally frets away the softer parts of islands, and nothing remains but fanciful clusters of rocks, and mere shreds and patches of masses once continents. We give below a view of the cluster of rocks to the south of Hillswick Ness, one of the Hebrides, from a sketch by
Dr. Hibbert. These fantastic shaped rocks, which are all that remain of what was once an island covered with vegetation, are striking monuments of that incessant change which, continually, though silently and almost unnoticed, is going on, but whose final effects are of the most magnificent character. Examples of such rocks as are figured above, are found in many places along the coast of the United States, where it is exposed to the action of the storms of the Atlantic. We may be able to form some idea of the degrading power of the ocean from the following statement, which is given on the authority of Lieut. Mather, geologist to the first district of the state of New York. “Vast masses of the cliffs of loam, sand, gravel, and loose rocks, of which Long Island is composed, are undermined and washed away by every storm. The water on the ocean coast, to some distance from the shore, is almost always found to have more or less earthy matter in suspension, much of which, except during storms, is derived from the grinding up of the pebbles, gravel, and sand, by the action of the surf. This earthy matter is carried off during the flood tide, and in part deposited in the marshes and bays, and the remainder is transported seaward during the ebb, and deposited in still water. After a close observation, I have estimated that at least 1000 tons of matter is thus transported daily from the coast of Long Island, and probably that quantity, on an average, is daily removed from the south coast, between Montauk Point and Nepeague Beach. This shore of 15 miles in length, probably averages 60 feet in height, and is rapidly washing away; 1000 tons of this earth would be equal to about one square rod of ground, with a depth of 60 feet. Allowing this estimate to be within proper limits, more than two acres would be removed annually from this portion of the coast. It is probable that any attentive observer would not estimate the loss of land there at less than this amount. Nearly one half the matter coming from the degradation of the land is supposed to be swept coastwise in a westerly direction. There are many evidences that the east end of Long Island was once much larger than at present; and it is thought probable that it might have been connected with Block Island, which lies in the direction of the prolongation of Long Island.” A remarkable exhibition of the conjoint power of waves and currents was exhibited during the building of the Bell Rock Lighthouse. The Bell Rock, on which it stands, is red sandstone, about twelve miles from the mainland, and from twelve to sixteen feet under the surface at high water. At a distance of 100 yards from the rock, there is a depth in all directions, of two or three fathoms at low water. During the erection of the lighthouse in 1807, six large blocks of granite, which had been landed on the reef, were carried away by the force of the sea, and thrown over a rising ledge to the distance of twelve or fifteen paces, and an anchor weighing 22 cwt. was thrown up upon the rock. We are informed by Mr. Stevenson, that drift stones of more than two tons weight, have, during storms been often thrown upon this rock from the deep water.
A.NcRoAcMMENTs of the skA, 229
The eastern coast of England has been greatly changed by the action of the waves, the ancient sites of towns and villages, being now sand banks in the sea. The whole coast of Yorkshire, from the mouth of the Tees to that of the Humber, is in a state of comparatively rapid decay; the inroads of the sea at different . points being limited by the nature of the soil, or the hardness of the rocks. Pennant, after speaking of the silting up, or filling up with water transported sand, clay, gravel, &c., of some ancient posts in the estuary of the Humber, observes, “But in return, the sea has made most ample reprisals, the site, and even the very names of several places, once towns of note on the Humber, are now only recorded in history; Ravensper was at one time a rival to Hull, and a post so very considerable in 1332, that Edward Baliol, and the confederated English barons, sailed from hence to invade Scotland; and Henry IV. in 1399, made choice of this port to land at, to effect the deposal of Richard II; yet the whole of this has long since been devoured by the merciless ocean ; extensive sands, dry at low water, are to be seen in its stead.” Instances like these are not rare, the towns of Cromer, and Dunwich, are both lost, swallowed up by the ocean, which is now encroaching at Owthone at the rate of about four yards a year. At Sherringham, in Norfolkshire, where the present inn was built in 1805, and the sea was a distance of fifty yards, the mean loss of land being about one yard annually, it was calculated that it would require about seventy years before the sea would reach that spot, but between the years 1824 and 1829 no less than seventeen yards were swept away, and a small garden only, was left between the house and the sea, and when Mr. Lyell in 1829 visited the place, he found a depth of twenty feet, (sufficient to float a frigate), where, only forty-eight years ago, stood a cliff fifty feet high. Mr. Lyell justly remarks, “If once in half a century an equal amount of change were produced suddenly, by the momentary shock of an earthquake, history would be filled with records of such wonderful revolutions of the earth’s surface; but if the conversion of high land into deep sea be gradual it excites only local attention.” The flag-staff of the Preventive Service station, on the south side of the harbor, has, within