PART OF A LETTER from Thos. Forster, Esq., F.R.S., to Mr. Machin, Prof. Astron. Gresham, Sec. R.S., concerning a New Island, lately raised out of the sea near Terceira. [From the Philosophical Transactions.] London, May 12th, 1722. "I have sent you a draft of the several bearings, and the captain's account of an island lately broke out of the sea, bearing south-east from Terceira, distance seventeen leagues. "John Robinson being master of a small pink-snow, called the Richard and Elizabeth from Piscataqua in New England, arrived at Terceira, December 10th, 1720, near which island he saw a fire break out of the sea. The Governor hired him to go with the said vessel to view it, and sent on board sixteen sailors and two priests. On Sunday the 18th of December, we got under sail, at twelve o'clock at night, and stood from Angras south-east. The next day at two o'clock in the afternoon, we made an island all fire and smoke; we continued our course till the ashes fell on our deck like hail or snow all night. We bore from it, the smoke and fire roared like thunder or great guns. At break of day we stood towards it again: at twelve o'clock we had a good observation two leagues south from it. We sailed round it, and so near, that the fire and matter it threw out had like to have done us damage in which consternation we all betook ourselves to prayers, being in danger of driving ashore; then a small gale at south-east sprung up and carried us clear to our great joy. The breeze was accompanied with a small shower of rain, which caused a great dust to fall on our deck with the said breeze we stood away for Terceira. The Governor informed us that the fire broke out the 20th of November, 1720, in the night, and that the prodigious noise it made caused an earthquake, which shattered down many houses in the town of Angra, and places adjacent, to the great terror of the inhabitants. We took several drafts of the island at several bearings in our sailing round, of which the enclosed is a copy. Prodigious quantities of pumice stone, and half broiled fish were found floating on the sea, for many leagues round the island, and abundance of sea birds hovering about it. So far the cap tain. "An acquaintance of mine informed me, that in his passage from Cadiz to London, the latter end of April was twelve months, he observed the sea from Cape Finister, almost to the chops of the Channel, to be covered with pumice stones, some of which he gave me. South, distant two miles. "This island is almost round, and supposed to be about two leagues in diameter. By good observation its latitude is 38° 29′; its longitude 26° 33'. The bearing and making it in sailing round is expressed in the drafts* above." [The following is Captain Tillard's account of the small island on the south-west coast of St. Michael, within a mile of the shore, and which he named after his own vessel.] The eruption producing an island broke out in about thirty fathoms water on the 14th of June, 1811, having been previously for two or three days preceded by repeated shocks of earthquakes, sensibly felt in the capital of the island of St. Michael, and throwing 'down several cottages and parts of the cliff next the south-west side near its vicinity. The first burst through the water was in three or four places about a ship's length apart, which occasionally subsided; on the 15th, the day I arrived off the island, the whole of these had become united, forming an immense column of white smoke, and occasionally throwing up black ashes from 50 to 100 feet high. On the 18th, having proceeded over land to within one mile of it, in company with the consul; shortly after my arrival, for the first time a small peak was discovered above the surface of the water, which at every subsequent eruption increased, and this so rapidly, that in three hours, the time we remained on the cliff, it had formed itself a complete circle of cinders above water, nearly twenty feet high, on the side towards the sea; but which always broke in on the side nearest the land, after a violent explosion, when the water rushed into the crater with the greatest impetuosity. The cliff we were standing upon was perpendicular, and about the height of the North Foreland; the volcano a short mile from the shore, ascertained by bearings from the extremities of a base of 800 feet, and since more accurately by cross bearings in the ship. The eruptions were now so violent as to throw up the ashes as much above the level of our eye as the volcano was below it, they were thrown up in a spiral form, the first succeeded rapidly by a second, third, and fourth, each one overtopping the other, so as to form an appearance like a group of magnificent pines; and which, as they attained their utmost altitude broke into smoke in the most fanciful forms imaginable, the most beautiful of which bore an appearance to innumerable plumes of ostrich feathers surmounting each other. The cloud of smoke as it expanded itself in a horizontal direction to leeward, attracting by its heat the water up into it by a quantity of water spouts, formed another extraordinary feature. These eruptions were accompanied by the most vivid flashes of lightning, with a noise like the continued firing of cannon and musketry, and slight shocks like earthquakes, though one was strong enough to loosen the edge of the cliff about fifty yards from where we were standing, and which fell with an amazing crash. Having on the succeeding day proceeded to sea, and again making * Several of these are given, but we have considered one sufficient here. the island on the 4th of July, I found the volcano perfectly quiet, and the wind obliging me to pass pretty near it, I went, accompanied by some of the officers, to explore it more narrowly, and on our approach, from its appearance was induced to land. The form of the island is nearly circular, about a mile in circumference at its base, and its altitude about 300 feet. On the side facing the land is an entrance into the crater nearly upon a level with the sea, and is about eighty or ninety feet diameter, from which there is a small stream running into the sea, about six yards across, and close to the waters' edge was so hot, as only to admit the hand to be dipt into it and taken instantly out again. I should conjecture that the crater is filled from the sea at high-water. About two boats' lengths from the beach we had seven fathoms water, and twenty-five fathoms about half a cable off. J. TILLARD. ON THE LONGITUDES OF THE PRINCIPAL MARITIME POINTS OF THE GLOBE. By Lieut. Raper, R.N., Sec. R.A.S. In the Philosophical Transactions for 1822, in a paper by Mr. Goldingham, will be found notices of observations made at Calcutta, Coringa, Masulipatam, Bombay, and Madras. Mr. Goldingham obtained by Jupiter's Satellites, 5h. 21m. 5s.; by these and other observations, he finally adopted 5h. 21m. 9.4s., or 80° 17′ 21′′. The results of 800 lunar observations, made between 1787 and 1792, gave 80° 20′ 16′′ or 2′ 55′′ too great, as was then considered. These observations are given in the Madras Observatory Papers, contained in three folio volumes, at the India House. Mr. Taylor, (astronomer at Madras,) gives Vol. I. Madras obs. 1831, by Jup. Sat. 5h. 21m. 5·4s., or and by moon culminating stars 5 21 3.8, or Which is adopted in the Nautical Almanac. In Vol. II. for 1832, he gives Jup. Sat. 5h. 21m. 21·8s. or and by moon culminating stars 5 20 55.6, or Which however he considered as 5 or 10 seconds too small. 80° 16′ 21′′ 80 15 57 88 88 80 20 27 80 13 54 In a letter from the Cape, dated January the 23rd, 1840, to Captain Beaufort, Mr. Maclear gives the results of corresponding observations of moon culminating stars at Madras and the Cape, in 1834, 1835, 1836, and 1837,* as follows. * These observations are now printing in the 11th vol. of the Mem, of the Royal Astronomical Society. ENLARGED SERIES.-NO. 11.-VOL. FOR 1841. 5 E Each result includes from two to four different stars. Only three observations of the second limb occur. The result of these 70 observations is stated to be 4h. 7m. 5-6s., with a probable error of +0.5s, Then 4h. 7m. 5-6s. added to 1h. 13m. 55s. (see Nautical Magazine, vol. 1839 p. 548,) gives 5h. 20m. 56-6s. Mr. Riddle has computed the longitude of Madras by comparison of similar observations made at Greenwich, Cambridge, and Edinburgh, in the same years. [Memoirs of the Royal Astronomical Society, vol. 11.] 56 By 54 corresponding observations at Greenwich 5h. 20m. 54.9s. "" 65 If we consider these three observatories as equally well established, and then attach to each result the weight proportioned to the number of observations, we obtain 5h. 20m. 55·7s., a result agreeing within 1s. of that depending on the Cape alone. We shall adopt accordingly 5h. 20m. 56s., or St. George's church is 2' 21" east of the observatory, and the flag-staff on the same meridian very nearly, or From the paper quoted above, by Mr. Goldingham, we have, by 180 do. Subtracting 2' 55" from these according to the correction applied to the lunars taken at the same time at Madras, as before-mentioned, gives Jup. Sat correcting the Tables D.L. Madras observatory, 1ch. 16d. 7° 24′ 12′′ 72° 57' 37" 72 57 55 72 54 52 72 53 26 72 53 9 The mean of all these is 72° 53′ 49′′. The place of observation, (in latitude 18° 57' 44" by 32 mer. alts. of the sun and stars,) being 3′ 19′′ N. and 13′′ E. of the light-house, gives for the latter 72° 53′ 26′′. Hosb. 1803. Flag-staff S.E. bastion of Castle, 10 obs. Jup. Sat. 72 57 40 Captain B. Hall, 1814 72 504 Captains Elwon and Moresby in their surveys of the Red Sea, and Captain Haines in his survey of Socotra, have adopted 72° 53′ 26′′. In a note to Captain Washington, Captain D. Ross quotes the position of the observatory, connected by Lieutenant Shortreed with the general triangulation of India, in 72° 51′ 15.6", as depending on Madras in 80° 16' 30" To this he states 1' 18.6" is to be added, for the position of the church, which is the point of departure of the marine surveys, and which would accordingly be thus placed 72° 52′ 34·2′′. According to this statement, the diff. long. between the church at Bombay, and the observatory at Madras is 7° 23′ 56", which subtracted from 80° 14' 0'' our adopted longitude, leaves for the longitude of the church 72° 50′ 4′′. Captain D. Ross in the note just mentioned quotes also other meridian distances from Madras, which we shall annex, viz. Hosb. D.L. Madras fl. st. Heyw. D.L. do. 7° 21' 45" Horsburgh seems to quote this difference as 7° 23′ 18′′, vol. 2, (1836,) page 398. McIntosh. D.L. do. Goldingh. D.L. do. 7° 25' 0" 7 25 42 The mean of these is 7° 24′ 7′′, which subtracted from 80° 16' 20' gives 72° 52′ 13′′, agreeing closely with the position above discussed as regards the observatory, but not the flag-staff. In a letter at the India House, of May, 1840, Col. Everest gives the long. of the light-house 72° 51′ 11.7"; stating, however, that the computations had not undergone revision, and that the result depended partly on the measurement of the Beda base which awaited verification. Since the receipt of that letter, Mr. Walker, (the hydrographer to the H.E.I. Company,) acquaints me that the Beda base has been verified. If, therefore, we apply the diff. long. between the above and Madras (in 80° 17′ 21′′,) or 7° 26′ 9′′, to 80° 14′ 0′′, we obtain for the lighthouse 72° 47′ 51′′. The flag-staff, which is 1' 30" east of the lighthouse, would, therefore, be in 72° 49′ 21′′; and the church which, with the saluting battery, is 16" west of the flag-staff, in 72° 49′ 5′′. Since however, the position is on the point of being definitively connected with Madras, we shall not, until the result is officially given out, make any alteration in the longitude employed in the extensive marine surveys of the Persian Gulf, Coast of Arabia, and Red Sea, namely, the church in 72° 53′ 26′′, which for the present we adopt. It will be proper, therefore, to bear in mind, that the longitudes referred to the church will be subject to a minus correction, which may be expected not to differ much from 4' 21", 188. Agoada Point. Jetty. Lt. ho. Lambton, D.L. Madras obs. 6° 28' 28" Moresby, D.L. Bombay We adopt 73° 45′ 32". 73° 45' 32" 0 56 4* This diff. long. applied to 73° 45′ 32" gives for Bombay, (church as we suppose) 72° 49′ 26′′, agreeing nearly with the position deduced. 189. Mangalore flag-staff. Lambton, trig. survey, 74° 50′ 53′′. Horsburgh quoting the trig. survey, adopts 74° 53'. Again, in the original list of the positions of the trig. survey, the diff. long. between Madras and this place is given at 5° 24′ 45′′, which applied to his long. of Madras or 80° 18'30", gives 74° 53' 45". The difference of the two longitudes 80° 18' 30", and 74° 50' 53" is 5o 27' 37". It appears from a document of Capt. D. Ross's (at the Geographical Society,) that the flag-staff has been moved one mile to the N.N.E.; hence, as we do not know precisely when this took place, we must be content to admit for the present a discrepancy, amounting however to only 22". 1° 59' 1" 1 59 41 0 24 Moresby, D.L. Bombay * Master of her Majesty's ship Andromache. 74° 52' 27" 74 53 7 74 53 50 |