it rests immediately on granite, and at the Muckish mountain contains a bed of pure siliceous sand of considerable thickness. The author proceeds to notice the ancient beaches of Jura which appear hitherto to have escaped observation: these occur on both shores of Loch Tarbert, and are disposed in six or seven terraces rising regularly from the present shore, above which the highest is elevated about 40 feet; the breadth occupied by these beaches, in some instances, amounts to three-fourths of a mile, and their line or extent has been traced eight or ten miles.

The author concludes with a description of, and remarks on, the trap dykes of Jura; these are extremely numerous, and remarkable for preserving courses nearly parallel to each other, and nearly in the line of dip of the quartz rock which they traverse, which gives occasion for offering some reasons to account for that particular disposition.

ARTICLE XV.

SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS CONNECTED WITH SCIENCE.

I. Composition of Morphia.

From the experiments of M. Bussy, it appears that morphia is composed of

II. Corrections for Moisture in Gases.

The following observations and formulæ are taken from the last edition of Dr. Henry's Elements of Chemistry, vol. i. p. 25:

Another correction, which it is often necessary to make in taking the weight of gases, is for the quantity of aqueous vapour diffused through them. It is obvious that all gases, which are specifically heavier than aqueous vapour, must have their specific gravity diminished by admixture with steam; and, on the contrary, all gases are specifically lighter than steam must have their specific gravity increased by that admixture. For the following formulæ, I am indebted to Mr. Dalton, who has obligingly stated them at my request.

that

"At ordinary temperatures, the tension or elasticity of aqueous vapour varies from 1-100th to 1-50th of the whole atmospheric pressure; in the present case it is supposed to be a given quantity. The specific gravity of pure steam compared with that of common air, under like circumstances of temperature and pressure, is, according to GayLussac, as 0-620 to 1.

"Let a weight of 100 cubic inches of dry common air, at the pressure 30 inches and temperature 60° Fahr.; p➡ any variable pres

sure of atmospheric air; and f = pressure or tension of vapour in any moist gas. Then the following formula will be found useful in calculating the volumes, weights, and specific gravities, of dry and moist gases; putting M for the volume of moist gas; D for that of dry gas; and V for that of vapour, all of the same pressure and temperature.

PD PV

D1 = Y

P f

"If we wish to infer the specific gravity of any dry gas from the observed specific gravity or weight of the same mixed with vapour, it will be convenient to expound p by that particular value which corresponds with a, namely 30 inches of mercury; and let s = the specific gravity of the dry gas, and w≈ the observed weight of 100 cubic inches of the moist gas.

Then we shall have the following, viz.

5.

30-f
30

6. $=

f

sa+ × 620 a = w.

30 - ƒ a

1. 98 vol. dry air + 2 vol. vapour 2. Given p = 30, f= 5, and M = 100. Then". M = D, the dry air, = 98±.

P

5. Let f = 5, s = 1·111, a = 30.5, p = 29′5,

Then

30-5
30

.5

1.111 x 30.5 + × 62 × 30.5= 33.64 = w, which

gives the specific gravity 1·103.

29.5

6. Let f, a, and p as above, and w = 2.5, corresponding to specific gravity 0-8197.

"The above formulæ apply equally well if V be a permanent gas, or any other vapour beside that of water, the specific gravity of the gas vapour being substituted instead of 620 that of steam."

or

* It is easy to see that V, in this and the other cases, mostly will denote a virtual vo lume only; or such as would result, if the vapour were condensible like a gas, without being convertible into a liquid.

III. Crystallized Steatite.

According to the analysis of Prof. Dewey, this mineral contains

"In heating the mineral, there was sometimes more and sometimes less than 15 per cent. of water liberated; but the water is taken at 15 per cent." The above proportions, it appears, are between those obtained by Klaproth in his analyses of steatite from two localities; "there can be no doubt, therefore," Prof. Dewey remarks, "that these crystals are real steatite."

Some

"The form of some of these crystals, is that of a six-sided prism terminated by six-sided pyramids, often variously truncated. of them appear to be four-sided prisms terminated by a four-sided pyramid. They are unquestionably the crystals intended by Jameson, as they are found in a similar situation to those mentioned by him, though they seem not to be pseudomorphous. The locality is described, vol. v. p. 249, of this Journal. They are sometimes covered with a very fine grained and close brownish steatite, in which, as in the asbestus, the crystals leave their form. The specific gravity of the crystals is less than that given to steatite. In the various specimens I have tried, it has been found very nearly 2, sometimes a little more or a little less. Their specific gravity may be taken at 2, water being unity."-(Silliman's Journal, vi. 334.)

IV. Earthquake and Volcanic Eruption in Java.

On the 27th of December, a shock of an earthquake was felt at Java, and it was repeated 18 times in 30 hours. At the same time, a subterranean noise was heard in the mountain of Merapic, which began to eject stones. On the 29th, at one o'clock in the morning, an eruption took place, during which half of the mountain was surrounded with torrents of lava and columns of fire, while a heavy shower of sand and small stones covered the environs. The village was destroyed, and 15 persons perished. At the mountain of Bruno, a very strong subterranean noise was heard, and it began to eject small black ashes which were perceptible at a considerable distance.-(Journal de Physique, tom. 96, p. 80.)

V. Glassy Actynolite.

The characters and constituents of glassy actynolite from Concord Township, Delaware County, Pensylvania, as determined by Mr. H. Seybert, are as follows:

Colour, in the mass, emerald-green; powder greenish-white. Lustre vitreous. Translucent. Fracture in one direction fibrous; in the opposite irregular. Very frangible. Scratches glass. Structurę

fibrous and fasciculated. Specific gravity 2.987. Fusible before the blowpipe into an opaque greenish enamel. It contains

The loss of weight by ignition is estimated as water in this statement. --(Silliman's Journal, vol. vi. p. 331.)

VI. Discovery of Mineral Caoutchouc in New England, United States. The following is Prof. Silliman's account of this discovery, as given in his journal, vi, 370:

"This remarkable mineral, hitherto nearly or quite confined to the Odin mine at Castleton, in Derbyshire, has been recently found at Southbury, 20 miles north-west of New-Haven. This region is a secondary trap basin, and although only six or eight miles in diameter, it presents all the characteristics of the great trap region of Connecticut and Massachusetts described by Mr. Hitchcock. Among other things, it contains slaty rocks with bituminous minerals; these have induced a search for coal which is now going on. We understand that they find bituminous slate or shale with small veins of coal. Specimens confirming this statement are now on the table, and they exhibit fibrous limestone, forming very distinct veins, or rather layers, running parallel with, and lying between, those of the slate. The fibres of the satin spar or fibrous limestone are one inch or more in length; they are often cracked in the direction of the fibres, and between them there are veins occupied by the mineral caoutchouc. It has but little elasticity, it is soft, easily impressible by the nail, and compressible between the fingers like potassium, and can be formed into a perfect ball; its colour is jet black; some varieties of it are a little harder, and have a resinous and splendent lustre, and a flat conchoidal fracture; it burns with extreme brilliancy, with much black smoke, and an odour between that of a bitumen and that of an aromatic; during the combustion, drops of liquid fire fall in a stream, or in quick succession, and with a whizzing noise, exactly like the vegetable caoutchouc, and it melts precisely as that substance does. Rubbed on paper, it leaves a black streak, and acquires a high polish; it does not remove pencil marks from paper. The veins containing this mineral are about one-quarter of an inch wide, and several inches long."

VII. On an Improvement in the Apparatus for procuring Potassium. By W. Mandell, BD. Fellow of Queen's College, Cambridge. "On repeating the late Prof. Tennant's experiment for procuring potassium (which differs from the similar one first made by the French chemists, Gay-Lussac, and Thenard, principally in being more simple

and commodious for practice), it occurred to me, that one part of the apparatus made use of, might, with advantage, be still further simplified; and as every circumstance, however apparently obvious, or trivial in itself, which, in any degree, tends to facilitate the production, in greater quantity, of so powerful a chemical agent as potassium, is of importance, I have thought that the mode of operating which I pursued might not be wholly unworthy the notice of this Society."

It is well known that the grand difficulty in successfully performing the experiment in question, consists in protecting the gun-barrelfrom the effects of that extreme and long-continued heat, which is necessary to decompose the alkali, and to volatilize its base. The usual practice hitherto has been to surround with a lute that portion of the gun-barrel which is introduced into the fire. This operation, however, is always tedious; and although it be conducted even with the greatest care, it is found extremely difficult to prevent fissures in the coating, particularly when the heat is much increased in the course of the experiment. Hence, if eventually the fire have direct access to the barrel, through any crevice which may be formed, the fusion of the denuded part is generally the consequence, and the whole labour of the experiment is lost."

"This then being the common cause of failure, it occurred to me that, if there were substituted for the luting, a thin but sound and well-burnt tube or hollow cylinder of Stourbridge clay, of such dimensions as just to cover that portion of the barrel which is subjected to the fire, the unfortunate result, which I have alluded to, might possibly be avoided."

"A tube of this description was accordingly procured; and in order to guard against the hazard of its cracking, by reason of exposure to a sudden increase of temperature, it was, in the first place, gradually and with caution, heated to redness."

"The remaining part of the experiment was then performed with entire success; and a very considerable quantity of potassium obtained."

"It may be proper to remark that the hollow cylinder, and that portion of the gun-barrel which it incloses, should be of such relative diameters that, when cool, their corresponding surfaces are not quite in close contact; otherwise the cylinder will be in danger of bursting, not only on account of its own contraction, but also on account of the simultaneous expansion of the gun-barrel, from the effects of that very high temperature, to which, in this state of combination, they are sub

mitted."

"Moreover, the whole apparatus should be supported accurately in the same position throughout the experiment (by means of rests made of Stourbridge clay), and should be so situate in the fire, that the materials operated upon may, during the whole process, be submitted to its greatest intensity."

"With due attention to these precautions, and to some minor circumstances in the manipulation of the experiment, which I shall not take up the Society's time in detailing, it is believed that the decomposition of potash, by means of iron, might, in every instance, be effected with almost entire certainty, and potassium be obtained in great abundance." (Cambridge Phil. Trans. 1822. Part II.)