into bays open to the north-west. The anchorage here, and at St. Helena, being on the north-west side of the islands may account for the rollers being said to come from the north-west; and it is probable that they are highest at the anchorages, from their being to leeward. The period when the rollers are said to come in from the northward being in December, at which time the sun is in high south declination, it is not improbable, I think, that the pressure may be greater to the northward than here, and hence propagate a wave in this direction. There is a singular, and as I am told regular, process observable here, and it appears consequent upon the rollers or their causes, which is a beautiful illustration of a nice adaptation of a universal law to individual habitudes, and another of the many proofs of design with which earth, air, and ocean are strewed, bespeaking a Creator, lavish in greatness, supplying all our real wants, bounteous in goodness and truth.* The selvage of sand round the bays where the turtle lay their eggs is increased considerably in breadth, during the season of incubation.

We are induced to add here the following extract, describing these rollers from the "Voyage of the Chanticleer," by Mr. Webster, her Surgeon, on account of its interesting nature, and the cause which he assigns for the phenomenon.-ED.

"One of the most interesting phenomena that the island affords, is that of the rollers; in other words, a heavy swell producing a high surf on the leeward shores of the island, occurring without any apparent cause. All is tranquil in the distance, the sea-breeze scarcely ripples the surface of the water, when a high swelling wave is suddenly observed rolling towards the island. At first it appears to move slowly forward, till at length it breaks on the outer reefs. The swell then increases, wave urges on wave, until it reaches the beach, where it bursts with tremendous fury. The rollers now set in, and augment in violence, until they attain a terrific and awful grandeur, affording a magnificent sight to the spectator, and one which I have witnessed with mingled emotion of terror and delight. A towering sea rolls forward on the island, like a vast ridge of waters, threatening as it were to envelope it; pile on pile succeeds with resistless force, until, meeting with the rushing off-set from the shore beneath, they rise like a wall, and are dashed with impetuous fury on the long line of the coast, producing a stunning noise. The beach is now mantled over with foam, mighty waters sweep over the plain, and the very houses at George Town are shaken by the fury of the waves. But the principal beauty of the scene consists in the continuous ridge of water crested on its summit with foam and spray: for as the wind blows off the shore, the over-arching top of the wave meets resistance, and is carried as it were, back against the curl of the swell, and thus it plays elegantly above it, as it rolls furiously onward, graceful as a bending plume, while, to add still more to its beauty, the sunbeams are reflected from it in all the varied tints of the rainbow.

"Amid the tranquillity which prevails around, it is a matter of speculation to account for this commotion of the waters, as great as if the most awful tempest, or the wildest hurricane had swept the bosom of the deep. It occurs in situations where no such swell would be expected, in sheltered bays, and where the wind never reaches the shore. The strong and well-built jetty of George Town has once been washed away by the rollers, which sometimes make a complete breach over it, although it is twenty feet above high water mark. On these occasions the crane at its extremity is washed round in various directions, as the weathercock is turned by the wind, and landing becomes impracticable for the space of two or three days. Such are the rollers of Ascension, and like unto them are those of St. Helena and Fernando Noronha. The season in which the rollers prevail is from December to April, although they do occur at other periods, and they have been felt severely in July. Ships at the anchorage are perfectly secure, and they have to apprehend no danger unless within the immediate influence of breakers. Not only are the seasons of the rollers the same at St. Helena and Ascension, but they sometimes are simultaneous in occurrence.

"The Chanticleer, while at anchor at St. Helena on the 17th and 18th of January, experienced some very high rollers, insomuch that Capt. Foster and his gig's crew ENLARGED SERIES.-NO. 3.-VOL. FOR 1843.

Y

In this process of extension it becomes shelving and easy of access, after which it appears to narrow to its original dimensions, and becomes precipitous, thus affording additional space and facility of gaining it.

Of the many vessels which arrived at Ascension from England, one only made a really good passage, owing to their going by the western route, or in consequence of standing over to the African shore, supposing no doubt that they would not otherwise fetch Ascension.

The course I should recommend, is to pass sufficiently far to the westward of the Cape de Verds, and continue till to the southward of their influence in order to avoid the calms, with rain in squalls which generally obtain under their lee. Then shape a course for 16° on the equator. This will bring you soon into the south-west wind which obtains generally throughout the year, and which will enable you to make southing to get out of the easterly current, the limits in latitude of which vary from the equator to 2° north. A westerly current obtains to the southward of this, and within narrow limits. Should you not have crossed the line before coming to 8° longitude go about if you can make a west course by compass on the port tack, from which you will fetch Ascension as you come up on drawing out from the African Coast. Several steamers have taken the eastern passage to the Cape of Good Hope, erroneously considering that they will invariably have land and sea breezes to aid them to the southward, and that they will be enabled to get fuel not only in sufficient quantity but with facility. The green wood which is to be had is a very insufficient fuel for obtaining full steam, and even this is not to be procured without delay. It is better far to coal at Ascension, but even this delay may be avoided by husbanding fuel on the passage from England.

may

For instance let a vessel leave England with fourteen days coals on board, and have also the ordinary amount of sail that our men-of-war steamers have, such as the Vixen. Then working expansively and taking advantage of the winds, she need not expend more than seven days coal before she arrives in the south-east trade, from which she must sail with one engine going to the southern limits which thus be reached by vessels such as the Vixen in eight or nine days, and the westerly winds may be reached in one day more, having expended then from twelve to thirteen days coal. These westerly winds will run her to the Cape in eight or nine days, or even to a position to fetch Maurilanded with the utmost difficulty. On our subsequent arrival at Ascension, I inspected the meteorological journal of my friend Mr. Mitchell, the Surgeon of the sland, and found it noted that the rollers were so violent on the 15th, 16th, and 17th of January, that landing was impossible. Here then, is a coincidence as to time. "The cause of the rollers have been speculated on, and various conjectures have been formed of them. Some have attributed them to the effects of the moon, "Whom Ocean feels through all his countless waves, And owns her power on every shore he laves.'"

year,

"And others have attributed them to the tides; but it is evident that these have nothing to do with them. They occur in the most tranquil season of the when the south-east trade wind is often very light, where the vast volume of water is constantly impelled in one direction. There is then a tendency to a back-set, or, a rush of water in a contrary direction, and a tumultuous swell is produced, wherever it meets with resistance from the islands and the banks on which they are based, as well as the shores of a continent. The long steep beaches of Ascension are admirably adapted for the full display of the effect which has just been described."

tius with the south-east trade in five days more. If she be bound to China this would be advisable, though in following this route she may have gone much to the southward of her direct course to the Cape, she will yet have attained to a latitude in which the degrees of longitude are so short as nearly to compensate for that but apparent great difference. Now, let it be supposed that the same vessel shall have gone to Ascension with only the same consumption of coals, or two days at least more. If she objects to make the detour necessary to fetch it under sail, this she cannot effect under two to six days more time. She will not then complete her coals, in the first case under six days, and in the second case under under eight days. She will not then reach the Cape of Good Hope if she steer direct in fourteen days time, and may be blown off by a south-easter, and then have to stand to the southward under sail, her coals being expended, while if she shape her course to the southward of a great sailing course as far as may be without increasing her distance above that of a direct course distance, she will have arrived in the westerly winds, which will run her into the Cape, so as to insure fetching, though a south-easter should catch her, and this in about fifteen days, perhaps with a saving of one or two days coals, which are valuable to contend with any unforeseen difficulties which might occur. For instance they might enable her to steam in against a north-wester. Then suppose a similar vessel to make the eastern passage, and to complete her coals at Fernando Po:she will not arrive at this place till six days at least after another may have reached the northern limit of the south-east trade;—she will then require six days to complete her coals;-she will not then reach the Cape, husbanding her coals as she may, under twenty days, for which she must have eighteen days fuel. If she stop any where to obtain the four days above her ordinary quantity, it will occupy fully eight days, if not eight days will not be more than enough to allow for completing the passage under sail.

The accompanying abstract will shew the relative values of each

route:

Probable passsges of three steam vessels of equal capacities from point of . divergence lat. 14° North, allowing that each has expended five days coals in reaching that point, then

If to Mauritius without touching at the Cape 12 days more, total

24

111

36 14

Eastern Passage touching at Fernando Po.

Expended as above

From divergence to Fernando Po

To complete coals at Fernando Po

From Fernando Po to Cape of Good Hope

She will require eight days to complete the quantity of fuel above stated

Should she not complete her fuel, she will require the above eight days to sail, and will then use but fourteen days fuel

Total from divergence with expense of fuel

If she do not stop to complete her fuel

Then coals being expended by sail, from Ascension to Cape

53

14

Total

14

At 2h. 30m. P.M. on the 14th of October, we left Ascension with a light and variable trade, and generally found ourselves to the northwestward of our reckoning, for though the current as appeared in the abstract, was but the difference between the dead reckoning and the observed, yet being with so very few exceptions, in one way it shewed the direction, though the amount may not be correct. Much of the amount however would appear to arise from the circumstance of the vessel overrunning the log, and when making westing the difference was westerly, and when making easting the difference was easterly. On the 19th of November we arrived at the island of St. Michaels, off which we anchored, with the city bearing S.E.b.E. F., on which bearing is the best anchorage, good holding ground, but very much exposed to winds from W.S.W.

to E.S.E. Experienced considerable difficulty in weighing with patent windlass; bad landing, and dangerous to boats alongside, from the heavy sea which sets in with southerly winds.*

Beef is easily obtained of good quality, at 34d. per pound. We found our chronometer 40' miles out owing to the concussion from firing (possibly), it being from a jump rather than an altered rate, at least such appeared to be the case, from our making St. Agnes at a distance rather to accord with the old rate than with the new.

We found 3° of decrease of heat in the water on getting into soundings. Part, but only part of this fall of temperature arose from changes of latitude, as appeared from the changes previously. It is also possible that part might arise from the coming east wind, which we afterwards experienced. This appears more probable as on the 18th we had an equal but contrary change and a southerly wind obtained.

On the 16th of November we experienced a rise of the barometer, and an E.N.E. by S. and S.E. wind followed, in strong squalls, indicating a change, and to the S.E. as the barometer fell a little. On the 19th we arrived at Spithead.

IMPROVEMENTS IN NAVAL ARCHITECTURE.

THE method of theoretic construction, which this paper is intended partly to elucidate, differs from every one that has been as yet set forth. It does not set out, as founded upon mathematical investigation; yet it will be found, whenever it shall be fully known, and examined, to be capable of sustaining the most rigid search, under that view; so that it will become refined, rather than destroyed, by such a process. It bears a very faint resemblance to some of the modes of Naval Architecture, already used and condemned; but it differs from them in this, that, while even the best of them, takes for the groundwork of its rules, a standard necessarily not perfect, although the best that was known at the time; this takes for its basis a standard derived from nature, consequently correct. In the application of this principle, the various results ascertained by science, and general experience, are taken to assist but not to control. For several years, the naval world has been violently agitated, between scientific and practical persons, as opposed to one another; not remembering, that science and practice if both true, must agree. The truth does not appear to have rested wholly with either, and while in their turn, they can each boast of very successful attempts, they have both also to acknowledge great failures.

The principle this paper sets out with is, that water, in passing obstacles, assumes certain determinate courses, which, it is presumed, are the curves of least resistance, under the existing circumstances. It is not deemed unreasonable, to construct a system of designs, mainly

* So many anchors have been lost off St. Michaels by vessels being obliged to slip their cables from bad weather coming on, that, the anchorage in many parts is foul. So much dispute has taken place about recovering lost anchors that the Governor gives none up to a vessel, that is not marked with her name.-ED.