ORIGINAL PAPERS.

SEPTEMBER, 1840.

OBSERVATIONS ON STEAM NAVIGATION TO SPAIN AND PORTUGAL,—with remarks on Major Rennell's Treatise on such "Currents of the Ocean" as affect it.

THESE remarks on a navigation, which most people will consider sufficiently well known, may, perhaps, at first sight appear superfluous to such as have not had some practice in Steam Navigation. But to those who have, it will be well known, that the courses adopted are so very different to those of sailing vessels, that although a man may have been all his life sailing, for instance, between England and Gibraltar, yet he will have much to learn of the whole coast, when undertaking for the first time, the conducting of a steam vessel; and which it becomes necessary to make himself acquainted with before he can make with confidence those direct runs, from point to point, which are essential to the quick passages of steamers. I have therefore put the following remarks together, to serve to quicken a conveyance, so fast progressing towards a general one.

Leaving Falmouth, a S.S.W. course, (compass courses and bearings always, except otherwise expressed,) clears the Manacles. A buoy has recently been laid off these rocks; it is very useful, and shews that this course will clear them well. But in night time, or thick weather, when the compass alone is the guide; I consider it is taking rather too much liberty with them, especially coming out of Falmouth to the west of Black rock; and that S.b.W. W. for half an hour, is no more than prudent. The mark used before the buoy was laid down, of "Mawnan church well open of Nare point till the Beast comes in sight," is very bad to make out, and should I think be made more conspicuous, either by a beacon placed upon it, or by being white-washed; and Nare point itself is very ill defined; a mark should be placed upon it likewise. (I have passed within the Manacles.)

Leaving the Lizard, a S.W. course will generally take a steamer just clear of Cape Torinana, which should always be referred to, as the S.W. boundary of the Bay of Biscay; and on which for the facility of Steam Navigation, a light is quite essential, and not on Cape Finisterre. ENLARGED SERIES.-No. 9.-VOL. FOR 1840

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In respect to the currents supposed to be generally in operation in the Bay, and which have often proved fatal, by setting ships out of their course, there can be no doubt of the fact. But be the wind as it may, I think a steamer should always steer S.W.; because the sooner she gets to the southward, and shuts out the British channel, the sooner she gets into fine weather. I am satisfied that on reaching latitude 47° the weather will, in tempestuous westerly gales, be found different there, than on reaching the same latitude, steering W.S.W.; because the latter course will keep the channel longer open, into which such gales have a tendency to draw; and of course you are longer in reaching this latitude. Nineteen times out of twenty, an observation will be got, on reaching 47°, by the course recommended, or at all events the day following; it will then be time enough to consider how the current is likely to operate on approaching the southern limits of the Bay, a sight for chronometers enabling you to ascertain how it has already acted upon the vessel's course, and the propriety of the course then to be adopted, must be come at, from the following considerations.

It seems to me to be quite clear, that admitting water to be forced into the Bay, along the north coast of Spain, at the commencement, and probably during the whole continuance of the S.W. gales, that this water must find its way out again, as supposed by the theory of the late Major Rennell, (in spite of the opinion of Captain Martin White) and it therefore appears probable, that a steamer keeping a straight course, that is to say, steering S.W. will make Torinana, the same as if no current existed at all; supposing the whole distance to be run, during a steady gale, which had blown for some days; and that the tides in crossing to the parallel of Ushant, had operated equally on the ship, which is probable would be the case. But it will be evident, that all the circumstances must be well considered: for instance, a ship leaves the Lizard at the tail of a S.W. gale. She will then probably experience a strong N.W. current in the early part of her passage. After getting past Ushant and falling calm, or the wind coming east, on reaching 47°, a S.W. course continued, will carry her right out of sight to the west of Torinana, because the waters will in such cases, instantly cease, being forced into the south part of the Bay, and will in fact there, as in every other part, set out to resume their level. Again, leaving the Lizard in fine weather, or in east wind, the probability is, that on reaching 47°, observations will place a ship in pretty nearly the situation, the course and distance would indicate her to be in. But should a gale then come on, from anywhere between south and west, it will be apparent, according to the theory admitted, that most serious danger would be the consequence, of not allowing for a very considerable inset into the south part of the Bay. For

it is probable that at the commencement of such gale, the water is impelled to the east along the north coast of Spain, at its greatest velocity. That at the conclusion of west gales, the whole water of the Bay recedes to the west, I can have no doubt whatever, and under such ciscumstances, the S.W. course will also carry you to the west of Torinana, which will also result from crossing the Bay during fresh easterly breezes. A view of these effects, caused by different winds, will readily determine the course after reaching latitude 47°, about which situation it may pretty well be calculated upon, that the violence of a S.W. gale will be lessened, if as recommended, a S.W. course has been adopted from the Lizard.

Much consideration is further necessary, as to the greater length of time a steamer is subjected to one current, more than to the other. She may be detained by very heavy gales, under the influence of the N.W. current, and feel comparatively little inset into the south part of the Bay, through a considerable abatement of the violence of the gale, enabling her to pass it quicker. It is clear according to the foregoing, that in returning across the bay, from the south, a serious error may also be made, by not duly considering these causes and their effects. Suppose the Bay to be entered at the conclusion of a S.W, gale, it will be sur charged with water, its level will be higher than the ocean and the certain tendency thereof, will be, to seek a return to the west in every direction. This will set a ship a long way to the west of the Lizard, in steering N.E., and in winter months, error in reckoning on the homeward passage is of the greatest importance, because the approach to the channel, is lessening the chance of correcting it by observation. The best plan under such circumstances, is to make Ushant, for though the lead would be a certain guide for the longitude, could you depend upon the distance run, so as to assume the latitude, with any thing like confidence; it will be found, that this cannot be depended upon, as in very bad weather, very great errors, are continually committed, in estimating the rate at which a steamer goes through the water, the log being of little use; and I am convinced it will require a very considerable experience, to come to any thing like a fair judgment on this point, a steamer being more impeded by sea, than wind, some more than others, under the same circumstances, and all differently affected in different trims. Again, if either outward or homeward, you enter the Bay at the commencement of a S.W. gale, the outset in the north of the Bay should not be reckoned upon. Coming from the south, you will pass so quick through it, that, especially should the wind be far west, you will find a strong indraught into the Bay right across; for there will not be time so to elevate the waters, as to cause them to force an outlet to the N.W., and this will be still more felt in crossing to the

south; should a gale come on when abreast of Ushant, it will be expe rienced in the whole run.

The opinion however entertained by Major Rennell and mostly adopted by writers of books of Nautical directions, though I entirely assent to it, as respects the water actually being forced into the Bay of Biscay, during heavy gales, from the west and south, as well as the same finding its way out to the N.W.; I must totally reject it when Cape Torinana is passed. I can find nothing to warrant the idea he has published; "of a general tendency of the water of the Atlantic, between latitude 45° and 30°, and from 100 to 130 leagues off the shore, setting into the Straits of Gibraltar!" Only imagine about 400,000 square miles (of surface) of water, continually moving towards a Strait eight miles wide! Why the least possible movement upon the remote part of such a superficies, would accumulate to such an amount, when collected at what may be almost called in comparison a point, as would cause a current greater than the imagination can figure to itself; and this current, according to the opinions entertained by the authority above quoted, is supposed to be, not merely a "surface current," but, (though not so stated in this particular instance,) we must believe from his opinions of the great currents of the ocean generally, to be supposed to extend to a very considerable depth.

It seems extraordinary how books of Nautical directions can contain such a statement, and almost in the same page, assert some strong facts (as they are called,) to shew that there is an under current setting out of the Strait, and that it runs out sometimes at the surface. Some very respectable authorities have asserted, that they have witnessed it running out. A ship coming out with a violent "Levanter" will pass out so quickly, as to give every appearance of having the current with her, but I should like some proof of its being so, rather than the mere opinions of seamen, however respectable, who appear to have adopted such opinions, under the circumstances I have supposed, namely coming out in a strong Levanter. The same is asserted of the waters of the Bosphorus sometimes running up, and there is not a man, forming an opinion from being in a boat, going up or down that Strait in a strong south wind, who would not at first view of his progress think the same, seeing the effect of the wind was such as to cause his progress to be so sensibly different, to what he had been accustomed to, or expected: but, nevertheless, I think that the waters of the Bosphorus running up, or those of the Straits of Gibraltar running out, may be shewn to be impossible.

Some facts have been stated, tending to shew, that the current does sometimes run out of the Straits of Gibraltar, such as sunken ships having been drifted on shore, much to the west of the spot where they

had been lost, and in fact making their appearance on the opposite side. But, as the tides are known to set out along each shore, it is by no means improbable, that the western tide may have set wrecks a long way in that direction; and that a strong wind acting obliquely on the Straits, and they (the wrecks,) floating at the surface, as they must have done, aided by the extraordinary eddies and races prevailing all over the Straits, may fairly account for the position in which they have been found. The idea of wrecks being set to the westward by an under current really seems to me the most extraordinary statement, and evinces a want of consideration unaccountable, on the part of those who have made it. The wrecks were, either floating or were at the bottom, one or the other is quite clear, if they had any heavy cargo in, or from any cause they were specifically heavier than water, they must have rested upon the ground! Does any one seriously believe that it is possible, even supposing the most furious current imaginable, that it would move a sunken vessel? But granting for a moment that it does so, would it not inevitably break her to pieces, before she had been propelled over the ground many hundred fathoms?!! If on the other hand, from the cargo or ballast washing out, or from any cause, the weight in the ship being got rid of, to the extent of rendering her lighter than water, (and which in the cases alluded to certainly took place,) then she would float at the surface, be under the influence of tides and winds, and have made her appearance, under these influences, probably to the westward, and perhaps even on the opposite side, in the manner already stated to have occurred, and her being proof of an under current, vanishes! How otherwise than from the effects of a strong "Levanter" did part of the wreck of the "Don Juan" drift from Tarifa, where she went to pieces to Cape St. Vincent? a westerly tide, and the wind having some southing in it, (it is generally S. E., immediately after leaving the Straits, during what is termed a "Levanter" at Gibraltar,) evidently set it there. No one supposes a current to run in that direction, though from what will be said hereafter, it will appear that within a line drawn from Cape St. Vincent to Tarifa, that is to say to the north of such line, there is a state of eddy and uncertain set of current and tide, at variance with, and often opposite to the general set towards the Straits, which would offer no opposition to this part of the wreck of the "Don Juan" drifting, by aid of wind, in the direction it did, nor interfere with the opinion already given, that in fact the current in the middle of the Strait is always to the east.

The great depth of water in the Straits, added to its constant current, seems to have defied any actual operations being carried on, to ascertain this long disputed point,-but such facts as could be come at, and upon which the latest charts have been constructed, have led to the drawing

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