author supposes of the same era with those which occur near Malvern, and at Ludlow and Wenlock-edge, and considers as the upper members of the graywacke series, and a link between the transition slate-rocks and succeeding formations.

2. Old red sandstone.

3. Mountain limestone.

4. Coal measures.

All the beds of this series are highly inclined, and thrown by their undulations into various basins, each of which contains a succession of coal-measures surrounded by bands, formed by the outcrop of the subjacent beds of mountain limestone and old red sandstone.

The principal of these basins are; 1. That of Somerset and South Gloucester, including the collieries of Mendip, Kingswood, and Sodbury.

2. That of the forest of Dean.

3. That of South Wales.

The second formation, beginning with the lowest beds, consists of

1. Calcario-magnesian conglomerate, and magnesian limestone. 2. Newer red sandstone and red marl.

3. Lias.

4. Oolite, which rises to a greater elevation than the three preceding beds, and skirts the eastern border of the district under consideration.

Besides these regular formations, two whin-dykes traverse the north border of the Somerset and Gloucester basin, near Berkeley, extending north and south nearly parallel to each other for about two miles, and cutting the transition limestone and old red sandstone. At one point, called Woodford, one of these dykes has been said to contain organic remains; but these have been found only in portions of the limestone, entangled, and partially enveloped by the sides of the dyke. This trap contains agates, prehnite, sulphate of strontian, carbonate of lime, green earth, and ferriferous magnesian carbonate of lime: the two latter abound in the amygdaloidal varieties at Woodford. In one spot near its south extremity, the dyke becomes columnar.

This paper contains some precise observations of the angles of inclination and direction of the different strata, which, though of little importance when taken singly, possess considerable value in reference to the structure of an extensive district.

A note points out the recurrence of magnesian limestone in all the formations from primitive dolomite upwards through transition limestone, oolite, and chalk, and also that it exists in the London clay. An appendix contains a list of previous works in which accounts of the district under examination may be found, and the authors have given a very brief but useful abstract of these contents.

A paper was read, on the rock of Gibraltar, by Thomas Kent,

Esq. communicated through William Cosens, Esq. both of Gibraltar.

The rock is a mass of limestone, whose greatest height is about 1,440 feet, and its base about 2,200 feet, in its longer diameter. The small rock on which the Devil's Tower is built, appears to be a fragment fallen from it: the edge of the summit is in some places so sharp that a person cannot stand upon it. Part of the rock appears to have been much broken and dislocated, and in the intervals between the fragments, as well as in a cavern in the side of the east cliff, bones have been found incrusted with stalactitic carbonate of lime. The hills near St. Roque, reaching for a distance of several miles into Spain, contain large oyster and cockle, and other shells; but the author has not examined the beds.

The ancient city of Carteia was built of the stone from these hills.

ARTICLE XII.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS CONNECTED WITH SCIENCE.

I. Durham Coal Field.

We understand that it is in contemplation at present to open the Coal Field of Durham into Yorkshire. In the mean time, a bill is to be brought into Parliament to carry a rail-way from Bishop Auckland to Darlington and Stockton. Mr. Stevenson, of Edinburgh, one of the most accomplished engineers of this country, has been called by the committee of subscribers to give an opinion as to the best line. The work is estimated at about 120,0007., a great part of which is already subscribed.

II. Melting Points of Bismuth, Tin, and Lead.

Mr. Creighton, of Glasgow, who has been long celebrated for the beauty and accuracy of the philosophical instruments made by him, and who has consecrated the evening of his life, in a great measure, to the manufacture of thermometers, has made some remarks on the boiling points of bismuth, tin, and lead, which deserve to be better known than they seem to be at pre

He announced his determination of the melting points of these metals in an early volume of the Philosophical Magazine; but whether the facts to which I wish at present to draw the attention of the chemical reader were noticed by him in his original paper, I do not recollect, as I have not the early volumes of that work at present by me. If they were noticed, they seem not to have attracted the attention of chemists; for i

am not aware of any chemical book in which they are mentioned.

The melting points of these metals, as determined by Mr. Creighton, are as follows:

Now the curious circumstance attending these metals is this: When they cool down to the melting point, bismuth instantly sinks 8°, and immediately rises again; tin instantly sinks 4o, and immediately rises again; while lead undergoes no change whatever, but remains stationary at 612° till the whole is congealed.

It is well known that water in certain circumstances may be sunk down considerably below the freezing point without congealing; but the instant it begins to congeal, it rises again to 32°, at which it remains stationary till the whole is converted into ice. The subsidence of the bismuth and the tin is obviously analogous to that of the water, and the subsequent rise is doubtless owing to the commencement of congelation in these metals. The curious circumstance is, that each sinks a definite number of degrees, and that lead does not sink at all. I conceive that these phenomena depend upon the latent heat of these liquid bodies. When water is cooled down below its freezing point, it gives out a portion of its latent heat. The evolution of the latent heat, as it congeals, raises the temperature to 32°, and keeps it at that point till the whole water is converted into ice. Bismuth and tin, in like manner, may be cooled down several degrees below their point of congelation, and the heat they give out is a portion of their latent heat. When they begin to congeal, that portion which becomes solid gives out the whole of its latent heat, and this evolution keeps up the temperature at the melting point till the whole has congealed. But the latent heat of lead is much smaller than that of the other two metals. It seems this metal is incapable of parting with a portion of its 'latent heat. The whole of it escapes at once in proportion as the metal congeals: consequently the thermometer must remain stationary. The latent heat of these three metals, according to the experiments of Dr. Irvine, is as follows:

Bergman states the specific gravity of copper at 9.3243 (De Niccolo, Opusc, ii. 263).

Cronstadt states the specific gravity of Japan copper to be 9.000. I have never myself been able to

meet with copper of even so high a specific gravity as that given by Cronstedt, though I have examined the purest copper used in this country for alloying gold, and in which I could detect no sensible quantity of any foreign ingredient. I was naturally anxious on that account to take the specific gravity of the best kinds of Japan copper. This I have been enabled to do by the kindness of Professor Jameson, who got a piece of Japan copper, said to be of the very best quality, from a gentleman who had been in the habit of dealing largely in that article of commerce in India, and had himself (for he was the captain of a ship) carried it from Japan to India in great quantities. I found its specific gravity only 8-434, and hence, I think, we may conclude, that the number assigned by Cronstedt for the specific gravity of copper is above the truth. Bergman's number, à fortiori, is also in

excess.

IV. Measurement of an Arc of the Meridian in India.

Many of our readers are probably aware that a trigonometrical survey of India has been going on for a good many years, at the expense of the British government in that country, and under the superintendence of British officers well qualified for performing a task of that kind. Lieut.-Col. William Lambton, F.R.S. of the 33d reg. of foot, took the opportunity of this survey to measure, at different times, an arc of the meridian from north latitude 8° 9'38" to north latitude 18° 3′ 23.6", being an amplitude of 9° 53′ 45′′, the longest single arch that has ever been measured on the surface of the globe. The full details of this great measurement are partly contained in the 12th volume of the Asiatic Researches; and will be partly inserted in the 13th volume of that work, which will not probably be published for these three or four years. Col. Lambton has inserted an abstract of the principal results into a paper, which has been published in the second part of the Philosophical Transactions for 1818. From that paper I shall take a few of the facts which are most likely to be generally interesting to European readers.

1. The mean length of a degree due to latitude 9° 24' 44" in fathoms, is ..

... 60472.83 The mean length of ditto due to lat. 12° 2′ 55′′, is.. 60487-56 The mean length of ditto due to lat. 16° 34' 42", is 60512-78

Thus we see that these measurements show the degree lengthening as we advance towards the pole. In this respect, they agree with all preceding observations, which demonstrate that the polar axis of the earth is shorter than the equatorial.

2. Col. Lambton has shown by a comparison of his measurements with the length of a degree as determined in France, in England, and in Sweden, that the compression at the poles amounts too of the length of the axis.

The comparison of the Indian measurement with the French measurement, gives for the compression.

The comparison of the Indian measurement with the English measurement gives 113 11

While the comparison of the Indian with the Swedish measurement gives for the compression.

The mean of these three comparisons gives, or almost for the compression at the poles.

3. From the preceding compression of, Col. Lambton has calculated the length of a degree of latitude from the equator to the pole. The following table exhibits the result of this calculation. The last column of the table gives the length of the degree of longitude at the latitude indicated in the first column of the table.

Lat.

Degrees on the meri-Degrees on the perpen-Degrees of longitude.

dian.

dicular.