were frequently drifted many miles out of their current upon this part of the coast.* If so, the course without knowing it, and in bad or cloudy course of the Gulf Stream as it disembogues in the weather when many days would intervene from Atlantic, must be a little to the West, instead of a one observation to another, the set of the current, little to the East of North as our charts represent though really felt for but a few hours during the it. My own information, derived from the obser interval, could only be proportioned out equally vations of an intelligent brother officer, goes to conamong the whole number of days. Therefore Na- firm this opinion; should it be proved correct, it vigators could have only very vague ideas, either will explain the anomaly often remarked upon by as to the strength, or the actual limits of the Gulf Navigators with regard to a stronger current in Stream until they were marked out to the Nan- the Gulf Stream off Cape Hatteras, than further tucket fishermen by the whales, or made known by South, for then, this circumstance may be accounCapt. Folger to Dr. Franklin. The discovery, ted for by the Chart course leading them on the therefore, of its high temperature assured the navi- outer edge of the Gulf Stream until it reaches the gator of the presence of a current of surprising Carolina Capes, where they again get into the velocity, and which, now turned to certain account, strength of it. would hasten, as it had retarded his voyage in a wonderful degree. The place of embouchure for the Gulf Stream, is about the latitudinal limits of the Trade winds, where calms and variables prevail; and where aid from currents is most desirable. Our West India Cruisers are continually passing up and down this part of the stream; a few turns to and fro across it, by them, would show how the thread of the current does lie, of which we are now ignorant. It might materially shorten the passage of vessels bound North from the Gulf. Such, at the present day, is the degree of perfection to which nautical tables and instruments have been brought, that the Navigator may now detect, and with great certainty, every current that thwarts his way. He makes great use of them. Col. Sabine, in his passage a few years ago, from Sierra Leone to New York, was drifted 1,600 miles of his way by the force of currents alone; and, since the application of the thermometer to the The Gulf Stream, as it issues from the straits Gulf Stream, the average passage from Eng- of Florida, is of a dark indigo blue; the line of land has been reduced from upwards of eight junction between it and the roily green water of weeks, to a little more than four. This may, in the Atlantic, is plainly seen for hundreds of miles. some degree, be owing to the improvement in ship Though this line is finally lost to the eye as the building, but it is less owing, I apprehend, to any stream goes North, it is preserved to the thermomincreased speed of vessels, than to a better know-eter for several thousand miles, yet to this day the ledge of winds and currents; for the "Constitu- limits of the Gulf Stream, even in the most fretion" and the "United States" are, at this day, the fastest ships in the Navy; and they are models of the last century. There is a current constantly setting into the Mediterranean to supply the waste, it is said, of evaporation. Now, on account of climate, the evaporation from the Gulf of Mexico in summer, must be much greater than from the Mediterranean; moreover, the rivers which empty into the Gulf are all at low water in summer; yet the Gulf Stream is said to run with much greater velocity in summer than in winter. If so, it is reasonable to suppose that the waters of the Gulf are higher at one season than another. But we have Light houses at the Tortugas, the Balize, Mobile and Pensacola, and keepers at them who would be glad of the employment. A tide staff planted at each, and daily registered for a year or two, would show whether there be a winter and a summer level to the Gulf, and thus settle this interesting ques tion. The manner in which the Florida Straits open out into the Atlantic-inclining to the Westward of North, the contour of the adjacent coast, the deep indent in the shore line here, between St. Augustine and Savannah, all seem to indicate a close pressure of the Gulf Stream and its counter quented parts of the ocean, though so plainly marked, are but vaguely described on our charts. Thousands of vessels cross it every year; many of them make their observations upon it, and many more, if invited would do the same. But no one has invited coöperation; consequently there is no system, and each one that observes, observes only for himself; and when he quits the sea, his observations go with him and are to the world as though they had not been. Captain Manderson of the Royal Navy published, many years ago, "An examination into the true cause of the Florida stream," which he ascribed to the Mississippi and the floods of the other rivers emptying into the Gulf. But judging from what we see going on daily in the Mediterranean, the water from the rivers, especially in summer when the Gulf Stream runs at the greatest velocity, are not sufficient to supply the waste of evaporation. Taking the hypothesis of the English officer for granted, it was asserted by another writer, that the velocity of the Gulf stream might be determin ed by the freshets in the Mississippi. Capt. Li *April 3. This opinion is still further confirmed by an thentic statements, which I have heard, that the islands o the coast of Georgia bear marks of abrasion from the sea, vingston put these theories to rest by showing that the volume of waters discharged through the Gulf Stream, exceeds what is emptied from the Mississippi by more than three thousand times. actually forced up an inclined plane, whose submarine ascent is not less than 10 inches to the mile? The Niagara is an "immense river descending into a plain." But instead of preserving its character in Lake Ontario as a distinct and well defin Upon the ruins of this hypothesis which Capt. Livingston had so completely overturned, he ad-ed stream for several hundred miles, it spreads itvanced the opinion that the velocity of the Gulf Stream "depends on the motion of the sun in the Ecliptic, and the influence he has upon the waters of the Atlantic." To this day our books on navigation quote this opinion without comment. The most generally received opinion, however, is the one repeated by Dr. Franklin, that the Gulf Stream is the escaping of the waters that have been forced into the Carribbean sea by the Trade winds; and that it is the pressure of those winds upon the water, which forces up into that sea a head, as it were, for this stream. self out, and its waters are immediately lost in those of the Lake. Why should not the Gulf Stream do the same? It gradually enlarges itself it is true; but instead of mingling with the ocean by broad spreading as the "immense rivers" descending into the Northern lakes do, its waters, like a stream of oil in the ocean, preserve their distinctive character for more than 3,000 miles. Moreover, while the Gulf Stream is running to the North from its supposed elevated level at the South, there is a cold current coming down from the North; meeting the warm waters of the We know of instances in which waters have been Gulf midway the Ocean, it divides itself and runs accumulated on one side of a lake, or in one end by the side of them right back into those very reof a canal, at the expense of the other. But they servoirs at the South, to which theory gives an eleare rare, sudden and partial, and for the most part vation sufficient to send out entirely across the Atconfined to sheets of shoal water where the rip-lantic a jet of warm water said to be more than ples are proportionably great. As far as they go, three thousand times greater in volume than the the pressure of the Trade winds may assist to give Mississippi river. This current from Baffin's Bay the Gulf Stream its initial velocity; but is it of has not only no trade winds to give it a head; but itself adequate to such an effect? To my mind, the prevailing winds are unfavorable to it, and for a the laws of Hydrostatics as at present expounded, appear by no means to warrant the conclusion that it is, unless the aid of other agents also be brought to bear. great part of the way it is below the surface, and far beyond the propelling reach of any wind. And there is every reason to believe that this polar current is quite equal in volume to the Gulf Stream. Are they not the effects of like causes? If so, what have the trade winds to do with the one more than the other? Supposing the pressure of the waters that are forced into the Carribbean sea by the Trade winds to be the sole cause of the Gulf Stream, that sea and the Mexican Gulf should have a much higher It is a custom often practised by sea-faring peolevel than the Atlantic. Accordingly, the advo-ple to throw a bottle overboard, with a paper stacates of this theory require for its support "a great ting the time and place at which it is done. In the degree of elevation." Major Rennell likens the absence of other information as to currents, that stream to "an immense river descending from a afforded by these mute little Navigators is of great higher level into a plain." Now we know very value. They leave no tracks behind them, it is true? nearly the average breadth and velocity of the and their routes can not be ascertained. But knowGulf Stream in the Florida pass. We also know, ing where they were cast, and seeing where they with a like degree of approximation, the velocity are found, some idea may be formed as to their and breadth of the same waters off Cape Hatteras. course. Straight lines may at least be drawn, showTheir breadth here is about 75 miles against 32 in ing the shortest distance from the beginning to the the "Narrows" of the Straits, and their mean ve- end of their voyage, with the time elapsed. I hold locity is 3 knots off Hatteras, against 4 in the in my hand a chart representing in this way the "Narrows." This being the case, it is easy to tracks of more than one hundred bottles. From show that the depth of the Gulf Stream off Hat- it, it appears that the waters from every quarter of teras is not so great as it is in the "Narrows" of the Atlantic, tend toward the Gulf of Mexico and Bemini by nearly 50 per cent, and that consequent-its Stream. Bottles cast into the sea midway bely, instead of descending, its bed represents the tween the old and the new worlds, near the coasts surface of an inclined plane from the North, up which the lower depths of the stream must ascend. If we assume its depth off Bemini to be 200 fathoms, which are thought to be within limits, the above rates of breadth and velocity will give 114 Of two cast out together in South latitude on fathoms for its depth off Hatteras. The waters the coast of Africa, one was found on the island therefore, which in the straits are below the level of "Trinidad," the other on Guernsey, in the Eng of Europe, Africa and America, at the extreme North or furthest South, have been found either in the West Indies, or within the well known range of the Gulf Stream. of the Hatteras depth, so far from descending, are lish channel. In the absence of positive information on the More water can not run from the equator, or the subject, the circumstantial evidence that the latter pole, than to it. If we make the trade winds cause performed the tour of the Gulf, is all but conclusive. the former, some other wind must produce the latAnother bottle thrown over off Cape Horn by ter; but these, for the most part, and for great an American master in 1837, has been recently distances, are submarine and therefore beyond the picked up on the coast of Ireland. An inspection influence of winds. Hence, it should appear that of the chart and of the drift of the other bottles winds have little to do with the general system of seems to force the conclusion, that this bottle too aqueous circulation in the Ocean. went even from that remote region to the so called higher level of the Gulf Stream reservoir. The other" fork" runs between us and the Gulf Stream to the South as already described. As far as it has been traced, it warrants the belief that it too runs up to seek the so called higher level of the Mexican Gulf. Midway the Atlantic, in the triangular space between the Azores, Canaries and the Cape de Verd Islands, is the Sargasso Sea. Covering an area equal in extent to the Mississippi valley, it is so The power necessary to overcome the resistance thickly matted over with Gulf weed (fucus natans) opposed to such a body of water as that of the that the speed of vessels passing through it, is Gulf Stream, running several thousand miles withoften much retarded. When the companions of out any renewal of impulse from the forces of Columbus saw it, they thought it marked the limits gravitation or any other known cause, is truly surof Navigation and became alarmed. To the eye, at a little distance, it seems substantial enough to walk upon. Patches of the weed are always to be seen floating along the Gulf Stream. Now if bits of cork or chaff, or any floating substance be put into a basin, and a circular motion be given to the water, all the light substances will be found crowding together near the centre of the pool, where there is the least motion. Just such a basin is the Atlantic Ocean to the Gulf Stream, and the Sargasso Sea is the centre of the whirl. Columbus first found this weedy sea in his voyage of discovery, there it has remained to this day, and certain observations as to its limits extending back for fifty years, assure us that its position has not been altered since that time. This indication of a circular motion by the Gulf Stream is corroborated by the bottle chart and other sources of information. If, therefore, this be so, why give the end-wardly rate. There is, doubtless, another force less current a higher level in one part of its course than another? Nay more. At the very season of the year when the Gulf Stream is rushing in greatest volume through the straits of Florida and hastening to the North with the greatest rapidity, there is a cold stream from Baffin's Bay, Labrador, and the coasts of the North, running to the South with equal velocity. Where is the Trade wind that gives the high level to Baffin's Bay, or that even presses upon or assists to put this current in motion? The agency of winds in producing currents in the deep sea must be very partial. These two currents meet off the Grand Banks, where the latter is divided. One part of it underruns the Gulf Stream, as is shown by the icebergs which are carried in a direction tending across its course. The probability is, that this "fork" continues on towards the South and runs into the Carribbean Sea, for the temperature of the water at a little depth there, has been found far below the mean temperature of the earth, and quite as cold as at a corresponding depth off the Artic shores of Spitsbergen. prizing. It so happens, that we have an argument for determining, with considerable accuracy, this resistance which the waters of this stream meet with in their motion towards the East. Owing to the diurnal rotation, they are carried around with the earth on its axis towards the East with an hourly velocity 127* miles greater when they enter the Atlantic than when they arrive off the banks of New Foundland. In consequence of the difference of latitude between the parallels of these two places, their rate of motion around the axis of the earth is reduced from 925† to 758 miles the hour. Therefore this immense volume of water, in passing from the Bahamas to the Grand Banks, meets with an opposing force in the shape of resistance, sufficient in the aggregate to retard it two miles and a half the minute, and this only in its East quite as great, retarding it towards the North, for its course shows that it is the resultant of two forces acting in different directions. If the former resistance be calculated according to received laws, it will be found equal to several atmospheres. And by analogy, how inadequate must the pressure of the gentle trade winds be to such resistance, and to the effect assigned them? If, therefore, in the proposed inquiry we search for a propelling power no where but in the higher level of the Gulf, we must admit, in the head of water there, the existence of a force capable of putting in motion and of driving over a plain, at the rate of 5 miles the hour, all the waters as fast as they can be brought down by 3,000 such streams as the Mississippi river-a power at least sufficient to overcome the resistance required to reduce from two miles *In this calculation the earth is treated as a perfect aphere, with a diameter of 7925.56 miles. Or 915,26 to 758,60. On the latter parallel, the current has an East set of about 1 miles the hour-making the true velocity to the East and on the axis of the earth about 760 miles the hour at the Grand Banks. and a half to a few feet per minute, the velocity | verted, spiral turning towards the West. Owing of a stream that keeps in perpetual motion one to the principle here alluded to, all currents from fourth of all the waters in the Atlantic Ocean. the Equator to the poles should have an Eastward The facts, from observation on this interesting tendency, and all from the poles towards the equasubject, afford us at best, but a mere glimmer of tor, a Westward. light, by no means sufficient to make my mind clear Let us now suppose the solid nucleus of this as to a higher level of the Gulf, or as to the suffi-hypothetical globe to assume the exact form and ciency of any other of the causes assigned for this wonderful stream. If it be necessary to resort to a higher level in the Gulf, to account for the velocity off Hatteras, I cannot perceive why we should not, with like reasoning, resort to a higher level off Hatteras also, to account for the velocity off the Grand Banks; and thus make the Gulf Stream, throughout its circuit, a descending current, and by the reductio ad absurdum, show that the Trade winds are not adequate to the effect ascribed. When facts are wanting, it often happens that hypothesis will serve, in their stead, all the purposes of illustration. Let us, therefore, suppose a globe of the earth's size, having a solid nucleus and covered all over with water 200 fathoms deep! and that every source of heat and cause of radiation be removed, so that its fluid temperature becomes constant and uniform throughout. On such a globe, the equilibrium remaining undisturbed, there would be neither wind nor current. And the poet's picture would apply to every sea: "Still as a slave before his lord His great bright eye most silently Let us now suppose that all the water within the tropics, to the depth of 100 fathoms, suddenly becomes oil. The aqueous equilibrium of the planet is thereby disturbed, and a general system of currents, and counter currents is immediately commenced-the oil in an unbroken sheet on the surface running towards the poles, and the water in an under current, towards the equator. The oil is supposed, as it reaches the polar basin, to be re-converted into water, and the water to become oil as it crosses Cancer and Capricorn, rising to the surface and returning as before. shape of the bottom of our seas and in all respects, as to figure and size, to represent the shoals and islands of the sea, as well as the coast lines and continents of the earth. The uniform system of currents just described would now be interrupted by obstructions and local causes of various kinds, such as unequal depth of water, contour of shore lines, &c.; and we should have, at certain places, currents greater in volume and velocity than at others. But still there would be a system of currents and counter currents to and from either pole and the equator. Now do not the cold waters of the North, and the warm waters of the Gulf made specifically lighter by tropical heat, which we see actually preserving such a system of counter currents, hold, at least in some degree, the relation of the supposed water and oil. Apparently, in obedience to the laws here hinted at, there is a constant tendency of polar waters towards the tropics and of tropical waters towards the poles. The Exploring Expedition crossed one of these hyperborean currents 200 miles in breadth at the equator. There is also one near our own coast, another on the West coast of South America, as well as several others elsewhere known to exist; but for obvious reasons they are, for the most part, submarine and but little understood. Counter to these are the Gulf Stream and the Lagullas current, besides numerous others more tial velocity of the Gulf Stream. Thus, without wind, we should have a perpetual and uniform system of tropical and polar currents. In consequence of diurnal rotation of the planet on Assuming its maximum velocity at 5 knots, and its axis, each particle of oil, were resistance small, its depth and breadth in the Narrows of Bemini, as before, the vertical section across would prewould approach the poles on a spiral turning to the sent an area of two hundred millions of square East, with a relative velocity greater and greater, feet moving at the rate of 7 feet 3 inches per until, finally, it would reach the pole and whirl second. The difference of specific gravity between about it at the rate of nearly a thousand miles the the volume of Gulf water that crosses this sectional hour. Becoming water and losing its velocity, it would approach the tropics by a similar, but in-line in one second, and an equal volume of water at the ocean temperature of the latitude, is fifteen millions of pounds. If these estimated dimensions (assumed here-as throughout this paper they have been upon the best authority, but merely for the purposes of illustration,) be within limits, then the force per second, operating here to propel The Gulf, or Carribbean Sea, may have, towards the channel of Yucatan, a higher level of a few inches and such only as is due to any other large stream of 3 or 4 knots when deflected in its course, as the Carribbean currents are, between their entrance into that sea and their exit from the Gulf. VOL. X-51 the waters of the Gulf towards the pole, is the equilibrating tendency due to 15 millions of pounds of water in the latitude of Bemini. as from other circumstances. If it did, the upper edges of its cold banks would support a lateral pressure of at least 100 lbs to the square foot; and In drawing up a plan for investigating the currents vessels, in crossing it, would sail over a ridge as of the seas, such agencies should be taken into ac- it were; on the East side of which, they would count. As a cause, I doubt whether this one is suf- meet an Easterly current; and on the West side, ficient of itself to produce a stream of such great a Westerly current. The resolution of the forces velocity as that of the Gulf; for, assuming its es- of each of these currents, with the Northwardly timated discharge to be correct, the proposition is set of the stream itself, would induce Navigators almost susceptible of mathematical demonstration, to report a North Eastwardly current as they asthat to overcome the resistance opposed in conse-cend the other side of this ridge, and a North Westquence of its velocity, would require a force at wardly current as they descend on this; yet never least sufficient to drive, at the rate of 3 miles the was it heard that the Gulf Stream runs North hour, ninety thousand millions of tons up an in- West. clined plane, having an ascent of 3 inches to the mile. Yet the very principle from which this agent is derived, is admitted to be one of the chief causes of those winds which are said to be the sole cause of this current. Should this roof current be too superficial to be felt by a vessel, the Gulf weed and all the floating substances borne by the stream across the Atlantic would run off on either side. But there is little or no Gulf weed along it WesBut, in addition to this, may there not be a pe- tern edge, and its prevalence on the Eastern side culiar system of laws not yet revealed, by which may be readily accounted for by the operation of the motion of fluids in such large bodies is govern- quite another law. Why this warm water thereed when moving through each other in currents of fore should not appear lighter than cold water is different temperature. That currents of sea water, a curious phenomenon that, as far as I know, has having different temperatures, do not readily com- never been considered. It is worthy of investi mingle, is shown by the fact already mentioned: that gation. Nor should the paradox as to a higher the line of separation between the warm waters of level-a double inclined plane in the Gulf Stream the Gulf and the cold waters of the Atlantic is itself, escape attention. Dr. Lardner assures us, perfectly distinct to the eye for several hundred and such too is the doctrine not yet exploded from miles; and even at the distance of a thousand our popular works,* that sea water expands accordmiles, though the two waters have been in contact ing to the laws of fresh; and from this circumand continued agitation for many days, the ther-stance he argues that the fish in polar seas are premometer shows that the cold water on either side served by the cold water being on top and the still performs the part of river banks in keeping the warm waters of the stream in their proper channel. warmer below. But deep sea soundings do not confirm this. With a surface temperature of 34°, Northern voyagers have obtained a temperature at In a winter's day off Hatteras, there is a differ- the depth of several hundred fathoms of 25°, which, ence between these waters of near 20°. Those according to the received laws of expansion, should of the Gulf being warmer, we are taught to be- have the specific gravity of water at 55°. And a lieve that they are lighter; they should therefore thermometer thrust down the throat of a fish caught occupy a higher level than those through which in polar seas, has been said to stand at Zero. The they float. Assuming the depth here to be 114 journals of arctic cruizers assure us of the fact, fathoms, and allowing the usual rates of expansion, that the deeper we go down in the Northern seas figures show that the middle of the Gulf Stream of America, the colder the water, while the warmth here should be nearly 2 feet higher than the con- off the shores of Northern Europe increases as tiguous waters of the Atlantic. Were this the we go down; thus showing a warm stratum of case, the surface of the stream would present a water to be lighter than the cold in one part of the double inclined plane, from which the water would Ocean, and in another contiguous to it, to be heabe running down on either side, as from the roof vier. of a house. As this ran off at the top, the same But to return to the mingling of the waters.weight of colder water would run in at the bottom; We know from a familiar experiment,† that oil and thus, before this mighty stream had completed placed on water in a state of rest exerts an obvi half its course, its depths would be brought up to ous and sensible force to put itself in motion; and the surface, and its waters would be spread out it is a fact well known to iron founders, that cold over the ocean. Why then does not such a body and therefore heavier iron, will not sink in the of warm water, flowing and adhering together * Dr. Marcet shows that sea water contracts until it through a cold sea, obey this law, and occupy a freezes. higher level? That it does not, we may infer from the silence of Navigators on the subject, as well * Supposing there be no resistance from friction. + If a bit of paper cut in the shape of a comma be dipped in oil and laid on water, the oil, in running off, will cause the paper to spin round. A cannon ball dropped into a ladle of melted iron will not sink till it expands, grows red hot, and becomes lighter. |