rock; and when the light bears W. N., you are well to the southward of the Boat rock. In beating through this channel, keep on the Albanian shore, it being all bold; and stand very little more than half channel over to the westward until you are well to the southward of the Sarpe rock.

"Vessels going to the northward will have no difficulty in observing these directions in a contrary order."

Directions for navigating the South channel." In coming from the southward of Payo, for the south channel, with southerly or south-westerly winds, you may pass between Payo shoal and light, or to the eastward of the shoal, at pleasure. To pass between the shoal and light, give Anti-Payo a good birth, and as soon as you open the light, bring it to bear N. W., or N. W. W., then steer for it, and keeping it on either of these bearings will lead you to the westward of the shoal; pass half a mile to the eastward of the light, and when it bears W. by S. S., you are to the northward of the shoal, and may keep away N. by W. W., or N. by W. When Payo light bears S. E., keep it on that bearing, and it will lead you well to the eastward of the buoy on the S. W. extremity of cape Bianco shoal. When the cape bears W. by S. S., or Black Island N. E. by E., you will be to the northward of the buoy, and may then steer N. W., or N. W. by N., according to the wind. You will then very soon get sight of Lefchimo light, which must not be brought to the northward of N. W. W. To keep you clear of Lefchimo shoal, which is a continuation of the one off cape Bianco, and runs along the east

side of Corfu as far as the light vessel, pass half a mile to the eastward of the light, and generally by this time you will see Corfu light; bring it to bear N. W. N., or N. W. N., then steer for it; pass half a mile to the eastward of it to clear Old Citadel Point, then steer in and anchor as before.

"Ships coming from the westward for the south channel, between the island of Payo and cape Bianco, should keep midchannel, or nearer to the former than the latter; steer in N. E. & N., or N. E E., and after opening Payo light, continue on the same course until the light bears S. E., then proceed as above.

"In coming from the southward, it will most generally be advisable to pass to the eastward of Payo shoal; then keep in midchannel, or rather the Albanian coast on board, it being all bold, and may be approached within half a mile. When Payo light bears W. by S.

S., you are to the northward of the shoal. When working through the south channel, while well to the southward of Lefchimo light, you may stand to the westward until the light bears N.-W.; but when within a mile of it, it must be brought to the northward of N. W. by W. W., to avoid the N. E. elbow of the shoal. The Albanian coast is all clear and bold to the southward of the light vessel; but after getting abreast of her, you must not stand within two miles of it, to keep clear of the Bacchante shoal. The Corfu side is then all clear, and you may stand well over towards it.

"All the above are to the nearest quarter of a point to the true bearings, or according to the poles of the world.

"The bearings and distances con

tained in the preceding directions were taken by W. Smith, esq., master of his majesty's ship Naiad. (Signed) W. ROBINSON." "Inspector-General of Ionian Ports and Coasts.

"Corfu, April 1, 1825." Currents of the Ocean. "In the voyage between Cape Mount and Cape Three Points, captain Sabine says that the Pheasant's progress appears to have been accelerated 180 miles by the current, which, in the season when the south-west winds prevail on this part of the coast of Western Africa, runs with considerable velocity in the direction of the land round Cape Palmas, to the eastern parts of the gulf of Guinea. In the passage between the river Gaboon and Ascension, being a distance of 1,400 geographical miles, the Pheasant was aided by the current above 300 miles in the direction of her course.

"But the more important distinction, both in amount and in utility in navigation, is between the waters of the Equatorial and the Guinea currents.-These exhibit the remarkable phenomenon of parallel streams, in contact with each other, flowing with great velocity in opposite directions, and having a difference of temperature amounting to ten or twelve degrees. Their course continues to run parallel to each other, and to the land, for above 1,000 miles; and, according as a vessel, wishing to proceed along the coast in either direction, is placed in the one or the other current, will her course be aided from 40 to 50 miles-a-day, or retarded to the same amount. On the day after the Pheasant sailed from Maranham, she entered the current, the full strength of which she had quitted to go to VOL. LXVII.

that place, and it was then found to be running with the astonishing rapidity of 99 miles in 24 hours. On the 10th Sept., at 10 a. m., while proceeding in the full strength of the current, exceeding four knots an hour, a sudden and very great discolouration of the water a-head, was announced from the mast-head: the ship being in 50 8' north latitude, and 50° 28′ west longitude (both by observation), it was evident that the discoloured water could be no other than the stream of the Amazons, pursuing its original impulse at no less than 300 miles from the mouth of the river, its waters not being yet mingled with those of the ocean, of greater specific gravity, on the surface of which it had pursued its course. It was running about 68 miles in 24 hours."Capt. S. continues, "On a general view of the currents which have been thus particularized, on the Pheasant's progress, in her voyage commencing at Sierra Leone and terminating at New York, it may be seen that she was indebted to their aid on the balance of the whole account, and in the direction of her course from port to port, not less than 1,600 geographical miles, the whole distance being under 9,000 miles; affording a very striking exemplification of the importance of a correct knowledge of the currents of the ocean, to persons engaged in its navigation; and consequently of the value of the information, in the acquisition and arrangement of which major Rennell has passed the latter years of his most useful life. The publication of the charts of the currents in the most frequented parts of the occan, which he has prepared with his accustomed and well-known indefatigable R*

assiduity, and strict adherence to the evidence of facts, (as soon as he shall deem them sufficiently complete), will be a most important service rendered to practical navigation."

Meteor.-Guelderland :-" The rains we had in August have contributed much to the improvement of the crops in general, especially after the great and intolerable heat of which I gave you an account in one of my former letters. In the latter end of August, a singular aerial phenomenon took place at 11 o'clock in the evening, viz.-a very considerable blue light was seen, which gave a most extraordinary appearance to all surrounding objects; so much so, that notwithstanding it was a full moon, and fine clear weather, it so frightened the servants, who were standing in the garden behind our house, that one of them came running into our room, in the greatest state of alarm, to mention the circumstance. The same appearance was noticed at the very moment through the whole country, which proves that the substance or combustible fluid which emitted it must have been at a great elevation."

Two Comets.-The following are particulars of two Comets at present visible in Europe:-

August 22, 1825.

At 1h 39' sidereal time,
Right Ascension 8h 1' 29.16"
Declination... 28° 9 56.78 N.

This Comet also has no appearance of tail; its observed place differs so little with that given in Eicke's Ephemeris, that by placing the instrument according to the data there given, the Comet will be easily found. It is not visible in the night glass, yet it is much more distinct than the preceding Comet. Passy, near Paris, Aug. 23, 1825.

Aurora Borealis. A late number of the Edinburgh Philosophical Journal contains a memoir by professor Hansteen, in which that eminent naturalist has sketched out a very bold and plausible theory of the Aurora Borealis. The connexion of that phenomenon with magnetism has been long remarked, and is further confirmed by the observations of the professor. He considers the Aurora Borealis as a luminous ring surrounding the magnetical pole, with a radius varying from 20 deg. to 40 deg., and at the height of about one hundred miles above the surface of the earth. It is formed, he thinks, by luminous columns shooting upward from the earth's surface, in a direction parallel to the inclination of the needle, and to the direction of the earth's magnetism; these columns render the atmosphere opaque while they pass through it, and only become

luminous after they pass beyond it. From the outer or convex side of the ring beams dart forth in a direction nearly perpendicular to the arch, and ascend towards the zenith; and if they are so long as to pass it towards the south, they collect in the south in a sort of corona or glory, which is situated in that point of the heavens to which the south pole of the needle points. Professor Hansteen finds that the observations made respecting the Northern Aurora are well explained by this hypothesis; and he has collected facts to show that a similar ring exists around the southern magnetic pole situated in New Holland, the northern being in North America. He infers further, though the stock of observations is rather deficient, that similar luminous rings exist above the two extremities of the secondary magnetic axis, in Siberia, and in Tierra del Fuego.

Chronometers.-The official report from the board of Longitude of last year's trial of chronometers has been published. The annual prize of 300l. has been awarded to Mr. W. Widinham, of East-street, Red-Lion-square, for the best chronometer, it having varied only 1 second and 80 hundredths of a second on its mean daily rate during the 12 months. The prize of 2001. has been awarded to Mr. J. M. French, of the Royal Exchange, for the second best chronometer, his having varied 1 second and 85 hundredths of a second during the 12 months; 85 hundredths of a second during the last 9 months; and 45 hundredths of a second during the last six months, on its mean daily rate. Mr. French's chronometer, No. 720, was made

the standard during Dr. Tiarks' survey to ascertain the longitude of Madeira in July and August, 1822; and its accuracy during the time it was under his care induced him to take the longitude of Madeira from it. Dr. Tiarks takes the mean of the whole 16 chronometers employed on the occasion, by interpolation; and the standard gives the same result as the whole 16, within two hundredths of a second. It appears that through the means of these chronometers, Dr. Tiarks has been enabled to discover a considerable error in the longitude of Madeira (as laid down by a former survey), and to find out where the errors lay. He was employed by the Admiralty, at the recommendation of the board of Longitude, in 1823, to find, by the use of chronometers, the differences of longitude between Dover and Falmouth, and Portsmouth and Falmouth; and for that purpose he was furnished with 29 chronometers from the royal observatory, including all that were on trial for the prize. On this survey, he has discovered an error in the longitude of these important stations, as laid down by former surveys, in consequence of the accurate rate of going of these chronometers. He has thus been enabled to establish the following results:-Longitude of Dover station, 5 min. 17 sec. 54. E.; Portsmouth Observatory, 4 min. 24 sec. 77. W.; Pendennis Castle, 20 min. 10 sec. 85.; Madeira, 1h. 7 min. 39 sec. 08. On this occasion, also, it appears that Mr. French's chronometer was the standard. The former survey had placed the longitude of the two latter places about 4 seconds less to the westward.

Natural Sources of Carbonic Acid Gas.-Bischoff and Nöggerath, in Schweigger's Journal, mention a pit on the side of the Lake of Laach, in which they found many dead animals, as birds of different kinds, squirrels, bats, frogs, toads, and also insects. On descending into the pit, and gradually sinking the head, they experienced the same sensation as when held over a vat in a state of fermentation. The quantity of gas evolved varies at different times. This evolution of carbonic acid gas is more striking in the volcanic Eifel. On the right bank of the river Kyll, nearly opposite to Birresborn, there is a spring named Brudelreis; a provincial name for a boiling spring, and applied to this because it is perpetually agitated by large bubbles of gas, the agitation being so great as to produce a noise heard 400 yards off. In its vicinity numerous dead birds are found, killed by the carbonic acid rising from the water; and persons who kneel to drink at the spring are driven back by the gas. As MM. Bischoff and Nöggerath approached this spring, they heard the noise of its ebullition at a considerable distance, and by approaching their faces to the surface of the turf in the vicinity of the spring, found that it was covered with a layer of carbonic acid gas. They did not observe any deleterious effects produced on the surrounding trees or grass. On emptying the basin no more water was collected, showing that it was rain, not spring water.

Electric Powers of Oxalate of Lime.---Some oxalate of lime, obtained by precipitation, when well

washed, was dried in a Wedgewood's basin, at a temperature approaching 300°, until so dry as not to render a cold glass plate, placed over it, dim. Being then stirred with a platina spatula, it in a few moments, by friction against the metal, became so strongly electrical, that it could not be collected together, but flew about the dish whenever it was moved, and over its sides into the sand-bath. It required some little stirring before the particles of the powder were all of them sufficiently electrical to produce this effect. It was found to take place either in porcelain, glass, or metal basins, and with porcelain, glass, or metal stirrers; and, when well excited, the electrified particles were attracted on the approach of all bodies, and when shaken in small quantity on to the cap of a gold-leaf electrometer, would make the leaves diverge two or three inches. The effect was not due to temperature, for, when cooled out of the contact of air, it equally took place when stirred; being, however, very hygrometric, the effect soon went off if the powder were exposed to air. Excited in a silver capsule, and then left out of contact of the air, the substance remained electrical a great length of time, proving its very bad conducting power; and in this respect surpassing, perhaps, all other bodies. The effect may be produced any number of times, and after any number of dessications of the salt. Platina rubbed against the powder became negative-the powder positive; all other metals tried, the same as platina. When rubbed with glass the glass became strongly negative,