: observations made by Mr. W. Wales, in Captain Cook's second voyage, is 38° 32′ 20′′ Ν. and 28°41′ 5" W.; the Requisite Tables give the town in this position, which tends to confirm the position shown in the Table. 4. The position of ST. GEORGE, as given in the Requisite Tables, is erroneous. It states that island to be in 38° 53′ 30′′ N. and 28° 10' W. The north point does not appear to be higher than 38°45′. 5. FLORES and Corvo. The longitude of these islands is given according to the results of Tofino only; having inferred, on comparison, that they are the most exact. Vide the Chart of the Azores, Canary Islands, and opposite coasts, with the harbours, &c., constructed by the editor, and published by the proprietor, of this work. The late Sir Home Popham, from several observations, lunar and chronometric, inferred the longitude of the North point of Flores as 31° 11', or 2° 30′ more to the westward than the position assigned by Tofino. VARIATION OF THE COMPASS.-At St. Michael's, in 1806, the variation appeared to be 23° W. At Flores, 1840 W. Mr. Read states that, not long since, the variation at St. Michael's appeared to have increased to 21⁄2 points, but that it has lately decreased. Captain Livingston, by mean of many observations, found it about 25° W. in 1818. This gentleman properly observes, that these differences may be ascribed to the volcanic commotions and ferruginous nature of the country. See Note on the variation at Tenerife, hereafter. Sta. Cruz, on the E. side [5] 28 43 But the general mean of the longitude of the Mole of Santa 0Cruz, from the observations of Captains Perouse, Bligh, Vancouver, and Krusenstern, of M. Quenot, and the Baron Alexander de Humboldt, is 16° 15′ 18". The latter, by a Berthoud's chronometer, made it 16° 13' 10", in 1799. 0 0 17 46 0 0 17 58 0 20 17 57 0 0/18 10 0 0 30 0 0 28 5 40 1780 NOTES. 1. FUNCHAL. The latitude of Funchal is well ascertained. The longitude was esti mated by M. Bory, in 1772, at 16° 56', as it now stands in the French Tables. Capt. Horsburgh, in his first edition, states that he found it, by good chronometers, 17°6′; and Mr. Wales's observations, by time-keeper, in 1772, gave 17° 6' 22". By an eclipse of the sun and eclipses of Jupiter's satellites, in 1788, noticed on Mr. Johnston's Survey of Madeira, it appeared to be 17° 5' W. Harrison's time-keeper, in 1763, gave 17° 10' W.; and Arnold's, on board the Grenville, 1775, only 16° 46′. The mean, by several chronometers of Capt. Charles M'Intosh, in 1809, gave 16° 50'; and those of Capt. P. Heywood, R.N., 1810, gave 16° 51'.. These differences were, at length, decided by our late respected countryman Captain Flinders; from whose observations, in H.M.S. ship Investigator, 1801, the latitude of the Road appeared to be 32° 37′44′′, and the greatest longitude, by any of six timekeepers, 16° 54′26′′. "This was given by Earnshaw's watch, No. 465, which had kept an uniform rate during fifteen months previously to its being brought on board. We made use of this watch to reduce some lunar observations taken a few days before arriving at, and others after sailing from, the place of anchorage; and the result was as follows: "Ten sets of distances, east and west of the moon, taken by Mr. Crosley, in Funchal Bay, and afterwards, with a Troughton's sextant, 16° 59′ 21′′. "Eight sets, east and west, taken by me with a Troughton's circle and two sextants, before and afterwards, 16° 51′28′′." Hence, west longitude of Funchal, by lunar observations--Mean 16° 55′24′′. The Variation, in 1811, was 21° W. Since the above was written, we have been informed by Mr. William Smith, Master of H.M.S. Ganymede, that, by observations taken 9th August, 1818, Funchal Road appeared to be in 32°37′33′′ N. Longitude, by chronometer, 16°55′30′′; by lunars, 16° 57′15′′. Mr. J. Town, Master of the Salisbury, in Feb. 1816, made the longitude, by chronometer, 16° 55′42′′. His Excellency Sir Thomas Brisbane, on his voyage to New South Wales, (1822,) obtained his time at the house of Mr. J. W. Gordon, at Funchal, by four excellent chronometers, from which the mean longitude was concluded as 16°54′36′′. At the same time the latitude of the tower, on Mr. Gordon's house, was found to be 32°38′ 19′′.7, and that of the Loo Rock 32° 37′53′′.8. The longitude given by Sir Thomas Brisbane, seems to have been confirmed by the Admiralty chronometers, under the care of Dr. Tiarks, in 1823, which gave for the longitude of the British Consul's garden 16° 54′ 45". (In time, 1h. 7m. 39s.) DESERTAS. Captain Flinders found the southern end of the Bujio to be in latitude 32° 24'20", which differs less than a mile from its position as given on the charts; and he discovered a small ledge of rocks projecting from under the cliffs at the S.W. part of this island. 2. PORTO SANTO. A plan of this island, from a Survey by Lieut.-Colonel Roberts and Captain Thomas Wolley, of H.M. ship Arethusa, 1802, states, in general terms, the latitude of the town to be 33° 2', and its longitude 16° 35', which is only 20 minutes East of the meridian of Funchal. But, upon a comparison of this statement with the different tables and charts, we are apprehensive that the difference should be at least 37 minutes, and have so assumed it in the Table. See the Chart of the Azores and Canary Islands, before mentioned. The Req. Tab. and Conn. des Tems, give the latitude of the middle of the isle 33°5′, and the longitude 16° 14'51", and 16° 17′ 30′′. latter appears to be correct. The 3. The SALVAGES.-The longitude of the Great Salvage, as lately furnished by Five British East-India Journals, differs from 15° 34' to 16° 1'. The mean result of these is 15° 48′ W. Yet we have not deemed this evidence sufficient to cause a deviation from the position assigned by M. de Borda. M. la Perouse has observed, "We were employed on the 18th of August, 1785, in taking observations off the Salvage, and I think its longitude may be fixed in 18° 13', 15° 53' from Greenwich,) and its latitude 30° 8'15". Lieut. Wm. Mudge, R.N., who, with Lieut. Vidal, surveyed the Great Salvage in 1820, places its south side in 30°7′ 39′′ N. and 15° 56′18′′. W.; and he says of it, "This island is obviously of volcanic origin, and consists principally of a dark-coloured black rock, the detached parts of which, as well as the whole, exhibit strong marks of fixed magnetic polarity. Even the dust of the roads, and of the floors of the cottages, has the same character as the rock itself, and may be gathered up, like steel filings, by means of a bar magnet. "The compass was singularly deranged at the three stations taken on the survey, and the extreme difference in its variations amounted to about seventy-two degrees, at a less distance than one mile. At the first station, one morning, Mr. Durnford, one of the party, laid down his watch, and on returning to the same place again it was found that the watch had gained two hours in the interval, an acceleration due to the magnetic action of the rock upon the balance." 4. TENERIFE.-The position of Sta. Cruz, given in the Table, has been sufficiently confirmed. M. la Perouse says, "Several observations were made at Santa Cruz, in Tenerife, which we think may be fixed at 18° 36′ 30′′ (16° 16′ 30′′ from Greenwich,) and 28° 27′ 30′′ Ν. But the situation of the Peak, as given in the Requisite Tables, is 5'33" more westerly than that given by M. de Borda. Mr. Dalrymple's observations, by chronometer, 1775, gave it 12 minutes more to the eastward. 5. PALMA. The observations of Captain L. Wilson, by chronometer, place the north point of Palma between 6 and 7 minutes to the East, and the south point 3 minutes to the West, of M. de Borda's positions. This is a farther confirmation of the accuracy of that excellent observer. On the 21st of February, 1818, Captain J. W. Monteath made the longitude of the Point of Santa Cruz, on this island, by chronometer, to be 17° 45' 30" W., and the latitude of Point Turco, on the North side, 28° 51′30′′ N., and longitude 17° 48′ 30′′ W. 6. FERRO. It is, however, suspected that the Isle of Ferro is placed a few minutes too far to the West; and, probably, if we assign to the middle of it the meridian of 18° 0', we shall be nearer to the truth. This meridian (the first meridian of the antients) has heretofore been assumed, by different geographers, as 17° 40′ and 17° 45′ W. VARIATIONS OF THE COMPASS.-Between Porto Santo and Madeira, the mean Variation is about 20 degrees. In the Road of Santa Cruz, Tenerife, it is rather less, if we may conclude that it has been correctly ascertained: but M. de Humboldt has noticed that the variation differs several degrees, according to the place where the observation is made, at the Mole, or at several points to the north, along the shore: and, he adds, we must not be surprised at these deviations in a place surrounded by volcanic rocks. "I remarked with Mr. Gay Lussac, that, on the declivity of Vesuvius, and in the inside of its crater, the intensity of the magnetic forces is modified by the proximity of the lavas. - Personal Narr. Vol. I. 117. According to Mr. Finlaison's observations, made in the Tartar, in 1819, the variation in the Road to Funchal was only 19° 20′ W. and in that of Santa Cruz, Tenerife, he found it 17° 20′ only. The N.E. Point...... The New Town The South Point The Survey of the Cape Verde Islands, by Lieutenants Vidal and Mudge, R. N.; taken by 16 13 20 22 59 40 order of the Lords Commis16 11 0 22 46 30 sioners of the Admiralty, in the 167 0 2259 30 years 1819, 1820, and 1821. 15 57 0 22 52 40 Leton Rock..... 15 48 0 23 13 0 15 19 0 23 16 15 7 30 23 17 15 640 23 14 0 The Survey of the Cape Verde 0 Islands, by Lieutenants Vidal 0 and Mudge. 15 19 30 24 49 30 15 0 30 23 29 0 14 53 40 23 34 0 14 58 30 23 47 0 REMARKS. In the former editions of this work, we gave a detail of the observations, 15 1 15 24 250 made at different times, for deter14 53 0 24 340 mining the situation of the Cape Verde Islands; particularly those made by Messrs. Fleurieu, Borda, 14 48 0 24 47 30 Verdun, &c., by Mr. R. Keilor, 16 34 30 24 30 16 38 0 24 30 0 16 28 30 24 22 0 16 46 0 24 45 0 16 54 0 25 30 4 0 17 12 0 25 9 20 17 4 0 25 25 45 16 55 0 25 22 0 17 5 30 25 2 40 NOTES. Captains P. Heywood, Mortlock, &c. The results, generally, in regard to longitude, placed the islands a few minutes more to the eastward. We then gave Porto Praya in 23°30′34′′, now given in 23°34′ 0": the Road of Bravain 24°45′55′′, now 24° 47′30′′: but to the western side of St. Antonio we assigned 25°25′, since confirmed, not only by the Admiralty Surveyors, but by Captain Monteath and other observers. 1. SAL. A particular description of Sal and all the other islands will be found in our third section, hereafter. 2. MAYO. In the course of the year 1819, while surveying the island Mayo, Lieuts. Vidal and Mudge found the hills upon which they were carrying on their operations so strongly magnetic that the needle belonging to the theodolite became wholly useless; the dip increasing so much that the needle could not traverse, in consequence of one end of it being drawn down to the face of the instrument, &c. 3. ST. ANTONIO.-Captain Krusenstern, in the relation of his voyage around the world, says, "On the 6th of November, (1803,) at day-break, we perceived the island of St. Antonio, at the distance of from 25 to 28 miles. As the wind was moderate, I held directly to the westward, to keep still more away from the land, as calms are very frequent in the neighbourhood of lofty islands. At noon we had an observation in 17° 55' latitude. The S.W. point of the island bore, at that time, S. 24° E., distant about 45 miles. I now steered W.S.W., and, as the wind freshened towards the evening, S.W. by W. The next day, at noon, the S.W. part of the island St. Antonio bore 868, distant about 54 miles; and I again held S.S.W. "The mean of a variety of lunar observations, taken this morning, made our longitude, reduced to mid-day, 26° 17′7". By the watches it was 26°24′ 40′′. I reckoned the longitude of the S.W. point of St. Antonio, by Arnold's large time-piece, No. 128, the best of our chronometers, 25° 24'0"." (Mr. Hoppner's Translation, page 53.) Captain Captain Flinders, in the relation of his voyage, (Vol. I. p. 26,) has said, that he found the variation near the western side of St. Antonio, in the evening of the 14th August, 1801, before making the land, 13°51′; and in the next evening, 13° 3', when four leagues to the westward. He had not an opportunity of making observations to determine the situation of the island, but, according to his estimation, it would appear to be even more to the eastward than the situation now assigned; as he supposed the high land near the S.W. point to be in 25° 12′ W. For further information, see the Chart of the Cape Verde Islands, Second Edition, published by the proprietor of this work, and see, also, the description of St. Antonio, hereafter. VARIATIONS.-In 1821 the Variation of the Compass near St. Antonio was found to be near 16 degrees: at Port Praya, St. Iago, 14° West. The mean variation allowed by Lieuts. Vidal and Mudge is 14°. |