They are mostly perpendicular in direction, and nearly circular in shape; although they often appear of an oval form when cut through in the precipices surrounding the Eaton quarries, because the plane of intersection is there, in reality, oblique, and inclined at an angle of about 80 degrees with the horizon. Several sand-pipes often approach very near to each other without any tendency to unite; see a. These pipes are filled with three kinds of materials: 1st, sand and pebbles; 2ndly, loose unrounded chalk flints; 3rdly, fine ochreous sandy clay, not impervious to water. The pebbles are chiefly of black flint, but a few are of white quartz. With these are sometimes seen unrounded fragments of sandstone, with a cement of oxide of iron; the whole agreeing with the contents of the deposit incumbent on the chalk, which at Eaton is about 20 feet thick. The clay is also similar to the finer portion of that found in the gravel above. As a general rule, the sand and pebbles occupy the central parts of the pipe, while the sides and bottom are lined with clay. Neither organic nor inorganic calcareoùs matter occurs in any part of the pipes where the clay is in contact with the chalk. Large unrounded nodules of flint, with their original white coating (bb), are dispersed singly and at various depths in the larger pipes. The smaller pipes are frequently crossed by horizontal layers of siliceous nodules, as at c, d, e, fig. 1., which still remain in situ, not having been removed with the chalk in which they must have been originally imbedded. Single flints, forming part of these layers, sometimes appear in the middle of a small pipe, as at d, fig. 1, surrounded and supported by sand, so that, at first sight, it is not easy to imagine how it can have retained its position during the substitution of the sand and gravel for the original chalk. But, these flints are usually of large size and irregular shape, and may be still supported at one extremity by the chalky matrix. Neither a loose nodule of flint, nor a heap of nodules, has ever been observed at the bottom of a Sand-pipe at Eaton. The middle of each pipe is generally filled with sand and gravel, and the outside and bottom with clay, which is sometimes horizontal over the chalk, as at f, fig. 1.

The age of the gravel and sand undoubtedly belongs to the Norwich crag; as there are not only casts of marine testacea, a characteristic of that formation, in the ferruginous sandstone at Eaton, but also some shells of the genera Mya, Mactrum, Cardium, and Mytilus, in which the calcareous matter is still preserved. One remarkable fact is, that the sides of these pipes are lined almost continuously with a fine clay, nothing similar to the materials, the gravels and pebbles, which fill up their centres, and appear evidently to have been precipitated from above, slowly and gradually after (probably at a much later period) the openings in the chalk have been made to receive them. The chalk on the edges of the pipes is in a most discomposed state and slightly discoloured, of a yellowish hue, as if from clay and sand, and extending to the distance of from one to five feet.

The details of the second locality have been communicated to Mr. Lyell by Mr. Wigham. These pipes, (fig. 2,) occur at Heigham, in the suburbs of Norwich, and are tortuous in their descent. The pit represented is 30 feet deep, and the chalk barely covered with vege-table soil. Its upper portion, 3 or 4 feet deep, is mixed with sand and gravel; a b are cavities in the chalk, from 10 inches to 2 feet in diameter, and are elbows of tortuous sand-pipes, the other parts of which have been removed in excavating the pit.

The layer of chalk flints, c, not being horizontal, implies the chalk to have been disturbed.

At Thorpe is a Sand-pipe, (see fig. 3,) 20 feet in diameter, which on entering the chalk, is filled with gravel, sand, clay, stones, and

(FIG. 3.-Upper portion of a Sand-pipe at Thorpe, near Norwich.) chalk-flints. It penetrates the rough 35 feet of chalk, tapering gradu

ally. Its course is regular through 10 feet of sandy strata, A A, overlaying the chalk, some beds of which, as at b, are rich in the shells of the Norwich crag. A layer of light coloured sandy clay, c, fig. 3, (indicated by dots) lines the sides of the pipe vertically, and horizontally beyond the opening. The dark bed, d, fig. 3, is an indurated layer of sand coloured by oxide of iron, which contains casts of marine shells, not only where horizontal, but where vertical, as far as the entry into the chalk.

At the junction of the chalk and overlaying sand occurs a layer of large flints, which have suffered slightly from attrition.

Mr. Lyell then proceeds to the origin of these Sand-pipes, and concludes: 1. That the chalk has been removed by the corroding action of water charged with acid, in which the siliceous nodules, being insoluble, were left in situ, in the smaller pipes after the calcareous matrix had been dissolved. 2. That, from the dispersion of the flints through the widest pipes, the excavation and filling of the pipes were gradual and contemporaneous processes; for, had the tubes been first hollowed out, flints must have fallen to the bottom from intersected layers in the chalk above. 3. As a corollary of the above propositions, we must hold that the strata of the Norwich crag had been already deposited upon the chalk hefore the excavation of the Sandpipes; and this is farther confirmed by the manner in which the layers in loose gravel of the pipe d, fig. 1, and the dark sand with casts of shells, e, fig. 3, have sunk into the pipe.

Mr. Lyell thus rejects all sudden and violent agency, whether for the erosion or filling of the cavities; and concludes that land in this country must have emerged from the sea after the deposition of the Norwich crag, and yet at a period anterior to that of an aqueous denudation which has removed large portions of a deposit overlaying the chalk, and which supplied the contents of the sand-pipes. But, as we know of no denuding agency capable of excavating great valleys in a flat country like Norfolk, except the power of the ocean, operating either at the time of the submergence of land or that of its emergence from the waters, we must infer from all the facts and reasonings set forth, that land, consisting of chalk covered by crag, was first laid dry before the origin of the sand-pipes, and then submerged again before it was finally raised and brought into its present situation.

265

Astronomical and Meteorological Phenomena.

NEW COMET.

Ar 28 minutes after 3 in the morning of December 9, (civil reckoning at Berlin,) Encke observed this Comet at the Royal Observatory at Berlin, where he found its right ascension to be 13 hours, 42 minutes, and 44 seconds; its southern declination being 11 minutes and 30 seconds.

At 31 minutes, 13 seconds, after 6 in the morning of December 10, (civil reckoning at Altona,) Professor Schumacher, at the Observatory of Altona, determined its right ascension to be 13 hours, 43 minutes, 45 seconds, and its north declination 8 minutes and 18 seconds; whilst at 2 minutes 42 seconds after 6 in the morning of the 11th, its right ascension, as observed by the same astronomer, was 13 hours, 53 minutes, 19 seconds, and 27 hundredths; and its north declination was 27 minutes 57 seconds, and 7 tenths.

On the 15th, it was observed at Hamburgh Observatory by Mr. Rumker, when at 24 minutes, 55 seconds, and 38 hundredths after 4 in the morning, (civil reckoning at Hamburgh,) its right ascension was 14 hours, 31 minutes, 59 seconds, 49 hundredths; and its north declination, 1 degree, 39 minutes, 33 seconds, and 49 hundredths.-Times, Dec. 24, 1839.

This Comet was also seen at the Cambridge Observatory on the mornings of December 28, 29, 30, 1839; and January 2 and 3, 1840. The apparent right ascensions and declinations, (exclusive of corrections for parallax,) were found on those days to be nearly as follows, at the subjoined times from Greenwich, mean midnight :—

This comet is a brighter and more considerable object than that of Encke, which appeared towards the close of 1838. It has a well-defined nucleus, which is either solid, or consists of very condensed matter. The tail is well seen in a telescope of very low power, extending in the direction from the sun, making an angle of about 54 degrees, with a circle through the pole.-Observatory, Cambridge, Friday Morning, Jan. 10, 1840.

SPOTS ON THE SUN'S DISC.

ON October 2, Count Decuppis observed an unusual number of Spots on the Sun's disc, and on a quarter before 9 on that day, per

ceived a small black spot entirely free from penumbra, and of entirely spherical form, which had advanced upon the disc, describing an arc of about seven minutes. Reiterated observations convinced him that it had, in the mean time, advanced towards the sun's limb to the extent of two minutes and 30 seconds. At three minutes after 9, when M. Decuppis attempted to make a new observation, the spot had disappeared.

A Correspondent of the Dundee Advertiser, in September, notes:— "The surface of the sun has of late presented a very striking and diversified aspect, when contemplated through a powerful telescope. The spots of all descriptions by which its disc is divaricated have been more numerous, and some of them much larger than have been observed for several years past. On Monday, the 2d inst., almost the whole surface of this luminary seemed to be diversified with large and small spots of every description peculiar to the sun. A cluster containing four or five very large spots, and about thirty or forty smaller ones, disappeared from the western part of the disc on Tuesday, but a very great number of both large and small spots still remain. At present (Sept. 4) there is a very large cluster approaching the centre of the disc, which consists of about eighteen large spots, the smallest of them not much less than the size of the earth, and some of them much larger. Besides these, there are within the compass of the same cluster above eighty smaller spots, which can be distinctly counted by means of an achromatic telescope magnifying 120 times, making about 100 spots in all within the limits of one cluster. The smallest of these spots cannot be less than from 500 to 900 miles in diameter. One of the spots which lately passed off from the western margin of the disc, measured about the 1-30th part of the sun's diameter, and consequently, must have been about 30,000 miles in diameter, or nearly four times the diameter of the earth; and, if it is to be considered as a solid body, it must be above sixty times larger than the earth. It contained an area of more than 700,000,000 miles. Besides the cluster noticed above, there are five other clusters nearer the western edge of the disc, containing several large, and a number of smaller spots, amounting in all to about seventy or eighty; so there are at present nearly 200 spots, great and small, diversifying the surface of this luminary. The largest cluster will likely remain for about eight days longer before it disappears from the western limb. Some of the other spots will disappear in the course of three or four days. There are indications of other clusters about to appear on the eastern limb. Each of the larger spots has a dark nucleus, surrounded with a penumbra, or fainter shade, nearly of the same shape as the nucleus. Some of the nuclei appear nearly round, others elliptical, others conical, and some of them are divided in the middle by a bright streak. When these spots are near the margin of the sun, they appear surrounded with a mottled appearance, such as is seen on some parts of the lunar disc, evidently indicating elevations and depressions, or, in other words, mountains and vales of very great magnitude. These mottled appearances generally precede the appearance of spots on the eastern limb, and plainly show that there is a very great diversity of surface