758-762

Extract from a letter to the Secretary of the Navy, from Lieut. Wilkes, commanding the United States South Sea Surveying and Exploring Expedition, dated on board the United States Ship Vinceunes, Harbour of Rio Janeiro, November 27, 1838.^[1]

I proceeded with the squadron for Madeira. We continued our cruise with light, favourable winds, without any occurrence of importance until the 6th of September, when, being near a shoal, laid down on the chart as St. Anne’s shoal, I deemed it fulfilling instructions, to delay sufficiently for the purpose of examining the same; and having fully explored the locality in and near the supposed neighbourhood, by spreading the vessels of the squadron to embrace a large circumference of the ocean, nothing of it was discovered. A few hours, however, after leaving this vicinity, we fell in with a large cotton wood tree, 120 feet in length and 15 feet in circumference, which was at first reported as a shoal; and if the sea had been at all rough it might, in passing, have been mistaken for one.^[2]

I have little doubt but similar trees have occasioned the frequent reports of vigias, or shoals, being in existence hereabouts. Our position at this time was in latitude 37° 0’ 37” north, and longitude 40° 41’ 54” west, and where any floating bodies drifted by the gulf stream would probably have been deposited, as there is little or no current, and that variable.

We arrived at Funchal, in the island of Madeira, on the 16th of September, after a pleasant passage of twenty nine days. I directed a party of officers to make an excursion to Pico Ruivo, the highest point in Madeira, for the purpose of ascertaining its barometrical admeasurement, in regard to which, doubts have existed, owing to a disagreement of those who have proceeded us. Our observations were conducted with great care, and the barometers used were of the best manufacture of Troughton and Simms. Simultaneous observations were made at the residence of the American consul at Funchal, who was kind enough to afford us every means within his reach to facilitate our various duties.

The party remained on the summit of the mountain over four hours, which afforded us an opportunity of making a number of simultaneous observations, the result of which, in giving the height of Pico Ruivo, was as follows:—The highest point of the peak above the consul’s garden was 6,181 feet. The cistern of the barometer at the garden above half tide carefully levelled, was 56.6 feet.

I feel much confidence in our result, although from the high standing of Captain Sabine. R.A., I feel some hesitation in putting it forth; but the fact of my being supported by such high authority as Dr. Bowditch and Dr. Heinekar, with whom we have differed only seventy-three feet, and one hundred and sixty-three feet, induced me to believe that some accidental error must have occured in Captain Sabine’s observations, or that he was misled by his guides, and stopped short of the summit of the mountain, as they attempted with our party.

It appears, also, that the different results made at three separate periods, and by different persons, approaching so near each other, would be more correct than that of Capt. Sabine, who makes a difference of nearly seven hundred feet.

We made, also, a series of magnetical observations on shore for dips and intensity, and established the rates of our chronometers by a portable transit. We made by them the longitude of the consulate at Funchal, in 16° 54’ 11” west.^[3] and found the latitude by observation to be 32° 38’ 11” north, all which assured me that our chronometers had been performing well since our departure from the United States.

On the 25th September, having completed all that was deemed necessary, we sailed from Madeira, and stood to the southward, intending to pass over and search for the different shoals and vigias laid down in our track. After passing the latitude of the Canary Islands, we experienced a north-easterly current of about half a mile an hour until we reached the latitude of Bonavista, one of the Cape-de-Verds, which sets in an opposite direction to the current said to prevail between these islands, in the longitude from 19° to 21° west. We hove to, and tried the current morning and evening, and always found the same result. The current log used was two kegs, with a distance line of five fathoms between them, the lower one being just loaded sufficiently to sink the air-tight one under the surface of the water, with the usual log line attached to the centre of the distance line, precluding the possibility of its being a surface current; besides which, the dead reckoning of the ship, and our observations gave the same result. On the 29th of September we passed into the coloured water, quite as green in appearance as that of fifty fathoms in depth, on soundings. On entering it, the temperature decreased one and a half degree, and rose two degrees on leaving it. We continued in it until the 2nd of October, having run a distance of450 miles. The vessels of the squadron repeatedly sounded with from one to three hundred fathoms of line, but no bottom was found.

The first reported shoal laid down on our route upon the charts was the Maria rock, in latitude 19° 45’ north, and longitude 20° 50’ west, which we stood for, and hove to, near the position, until we ascertained our situation correctly, by careful observations. The vessels were then spread and the course marked to run directly over the spot; the surface of the ocean visible at the time from the squadron, was not less than 60 miles in circumference, with every opportunity which the clear weather could afford, and sufficient swell of the season to have caused breakers on any shoal within 15 feet of the surface. Nothing, however, was discovered, and no bottom could be found with 300 fathoms of line.

The next position examined was Bona Felix shoal, said to be within 30 miles of Maria Rock; this we searched for in the same manner, but were equally unsuccessful. We then stood for the place assigned the Bonetta shoal, to the eastward of Bonavista, said to be in latitude 16° 32’ north, and in longitude 20° 37’ west. We in like manner hunted for this, and, after exploring the locality of its position on the chart, I steered on the course of its reported bearing, east by north from Bonavista, until nearly up with the Hartwell reef, lying in sight of Bonavista which has, without doubt, been taken for and reported as the shoal called Bonetta.

Our enquiries at St. Jago assured me that the Madeline (the vessel last wrecked) was cast away on the Hartwell reef, which they have reported as the Bonetta shoal.^[4]

I am well satisfied that the positions assigned the above three shoals on the chart, and their vicinity, are free from all dangers. I am of opinion, also, that the particular and indefatigable search made by Capt. Bartholomew, of her Majesty’s ship Leven, and the opportunities afforded me of covering, with the squadron of five vessels, so large a space, at the same time, ought to be sufficient evidence that no such dangers exist as are laid down in those positions, and should cause them to be obliterated from the charts.

From Port Praya, we steered for Patty’s overfalls, as laid down in the chart, in latitude 11° north, and longitude 24° 30’ west, and had a good opportunity of examining their locality. A few rips were observed within a degree of the situation assigned them, but little or no current was found; and I feel confident in asserting that no danger exists in this vicinity, as we were becalmed in the position, and in close proximity to it for 48 hours, the squadron as usual being spread apart, and having a broad expanse of ocean under view. Owing to light contrary winds it was some days before we reached Warley’s shoal, said to be in latitude 5° 4’ north, and longitude 21° 25’ west. This point was carefully examined, but no shoal or appearance of shoal water, or any danger discovered.

Our next examination was of a French shoal, said to be (as laid down in latitude 4° 5’ north, and longitude 20° 35’ west. This was also examined and no danger or appearance of shoal discovered. From this point, I took advantage of the southerly wind, and proceeded west; which carried me as far as 13° of west longitude, and over the position assigned the shoal by the French hydrographers, to enable me to cross the equator eastward of the 17th degree of west longitude. We succeeded in crossing the equator in that longitude on the 5th of November, and then stood for Triton’s bank, said to be in latitude 00° 32’ south, and longitude 17° 46’ west. When within a short distance of its position, the squadron hove to, for the purpose of ascertaining our position accurately; after which a course was steered nearly west. Being at that time well to the eastward, we ran on line due east and west over it; the vessels of the squadron being spread about three miles apart, on a line north and south. We did not, however, find it in our progress, or any bottom or indications of soundings; no discolouration of water was visible, or change of temperature, although the line extended 30 miles east and west of its reported position; after which we again stood to the north, and ran over a vigia as laid down on the charts, but none such was found in existence.

Our next examination was for Bouvert’s Sandy island, which was in like manner carefully searched after, in and around its position as laid down on the charts, but our search was equally unsuccessful. Finally, search was made in and about latititude 2° 43’south, and longitude 20° 35’ west, extending to the north north-west of this point a distance of thirty miles hereabouts, having been assigned as the situation of the submarine volcano reported by Admiral Krusenstern, which it was supposed might have left a shoal. This locality was twice run over in different directions, and carefully examined, with the squadron in open order, but none such was found in existence.

Lieutenant Hudson, of the Peacock, having separated from me on the 16th of October, proceeded on a different course in search of the same shoals which we were looking for, but was equall unsuccessful in finding any, as appears by the following extract from his report to me, which affords further evidence, if it were needed, of their non-existence.

“Having separated from you on the 16th of October, it was not until the 23rd, that I had worked up to the Warley’s shoal; and at 8 o’clock that night I was directly on the spot where it was laid down on the chart. We placed good lookouts, and kept our patent lead going for fifty miles before reaching the location of this shoal as laid down on the chart; also observing our drift at night, in hopes of sweeping over it at early daylight. I continued cruising in this vicinity in various directions, getting casts of lead in from 50 to 100 fathoms, without finding bottom. I now continued my examination, and after having swept over a circle of 40 or 50 miles in different directions, am perfectly satisfied that Warley’s shoal exists no where in the neighbourhood laid down on the chart. I then proceeded for the French shoal with the wind ahead, (south by west,) where I arrived on the 25th of October, and continued cruising all the following day, with a fine breeze, immediately over the location of the shoal, as laid down, and in every direction for miles in its vicinity. After thus thoroughly searching the English locality of this shoal I directed my course for the French position, seventy-six miles distant, making nearly an east course, with lookouts, and the lead going, until I had run immediately over and around the spot, sailing in various directions, a distance of forty miles, without effect. I then made the best of my way for the Triton bank, with the wind veering and hauling from south-south-west, to south south-east, and passed the equator on the night of the 3rd November, in longitude 17° 40’ west, and continued over and around the locality of that bank, until the morning of the 5th, getting casts of the lead during the time in from fifty to two hundred and fifty fathoms, up and down, without finding bottom. I have in our search fully satisfied myself, and hope our examination will prove equally so to you, and all others, that these shoals do not exist.”

Thus, sir, we have effected the examination of the supposed position of eleven shoals or dangers, which have occupied their places on the charts, much to the alarm of navigators. And I sincerely trust that the result of our endeavours and diligent search, with the exertions heretofore made by others, will be sufficient to cause them to be obliterated from the charts, as there are already real dangers sufficient to awaken the watchfulness of the navigator without his being harassed with imaginary ones.

[1] In p. 576 of our August No., will be found Lieut. Wilkes’s letter from Terra del Fuego.

[2] Capt. Vidal, R.N., in his search for Aitkin’s rock in the Onyx and Leveret in 1831, whose proceedings we noticed in our vol. for 1831 and his chart in 1833 makes a simila remark, and that Aitkin’s rock was neither more nor less than an old tree. –Ed. N.M.

[3] Lieut. Raper discusses the longitude of this place in our August No., p. 545, making it 16° 54’ 45”. The present determination in being chronometrical will depend on the meridian measured from.–Ed. N.M.

[4] See p. 102 of our Vol. for 1837 for similar opinions.