the road to Launceston, similarly associated, with the additional accompaniment of intercalated killas and Coddon Hill grit dipping beneath the volcanic ash of Marly Mead. Mr. Williams also mentions a shaft sunk in a copper lode close by the turnpike gate on the road from Tavistock to Callington, as another instance of floriferous grit, or a rock exactly the same as that which contains the copper lode of Wheal Friendship, underlying pale green slate or killas: and he adds, there can be no doubt that Wheal Friendship mine is in No. 9 or the floriferous series. The next instance mentioned in the paper, is at Linkinghorn and South Hill, north of Callington, where there is stated to be an entire suite of alternations of killas, Coddon grits, and floriferous grits with plants, all dipping south. Again, near Pillaton, between Callington and Saltash, there are said to be countless minor alternations of floriferous and Coddon grits, each thinning out and interlocking like the teeth of a trap. Another instance of the killas overlying the floriferous grit, is said to occur in a hill at Penter's Cross on the road from Callington to Saltash, where a cutting exhibits in the lower part, a series of alternations of floriferous sandstone, and culmy slates which in ascending disappear, and in their place a delicate pale green killas alternates with the sandstone beds, while at the summit the sandstones disappear and are replaced altogether by killas. A fault traverses the hill, and to the south of it only killas occurs.

The general results of his observations, Mr. Williams says, show, that in the ascending order, from Cannington Park and the Quantocks in Somersetshire, to the Land's End, there is a group constituted of ten strikingly simple, consecutive series, severally varying in their mineral and zoological character; that as respects the limestone suites, the thin and spare dimensions of such as occur in the Trilobite slates of Exmoor (No. 7) render them too insignificant to be noticed; that the Posidonia limestones, which by mineral gradation succeed and conformably overlie the latter, are elliptically included in the Coddon Hill grits (No. 8), and together distinctly underlie and constitute the base of the great floriferous series (No.9): that higher up in No. 9 is an extended horizon, which separates the series into an upper and a lower, containing the Bampton, Hockworthy, Holcomb Rogus, and Hastleigh limestones, with red and black slates on the north; the Petherwen and Landlake slates and limestones on the south; and the entire suite of coral limestones to the east of Dartmoor, extending from Chudleigh to Berry Head and Brixham: that the Plymouth limestones included in the killas (No. 10) are higher in the group than those just mentioned, and are introduced first at Millaton, about a mile and a half west of St. Germains.

Mr. Williams considers the slate or killas series of S. Devon to be distinguished from the slates of Exmoor by a peculiar extraneous cleavage. In Exmoor the cleavage, he says, is at all angles, from less than 10° to the vertical, its planes having a direction of about east and west; whilst the cleavage lines of the killas either coincide with the magnetic or true meridian, or depart from it to the east or west only a few degrees, and the inclination approaches the vertical with a strike N. and S., or nearly perpendicular to that of Exmoor.

What, says Mr. Williams, are the results, if the question be tested by the assumed law, that strata may be identified by their organic remains? If the Posidoniæ and Goniatites of the lenticular, black limestones, never exceeding thirty-five feet in thickness, be appealed to, to identify them with the mountain limestone, the weight of organic remains opposed to them in the Launceston and Petherwen fossils, the corals and other organic remains of South Devon belonging to the floriferous series, reduces the evidence to dust. If mineral characters be appealed to, he says, they fail altogether.

In conclusion, Mr. Williams remarks, that in this supplement, he has endeavoured faithfully to transfer the simple truths of nature to his pages, without reference to the theories of others. He would, however, remind geologists that the proposed law of Mr. W. Smith is no law, if it do not imply a final and universal extinction of species. This being his own view, Mr. Williams says, he could not admit that the Goniatites and Posidoniæ of Devonshire were first introduced and became extinct with the mountain limestone, being justified by the fact of superposition, and more reasonable analogy, in concluding that these genera existed elsewhere in congenial conditions during the entire period of the deposition of the Trilobite slates, when that formation ceasing in Devonshire, the ova of the creatures or the creatures themselves were transported to a region favourable to their existence, and were continued during epochs of duration up to the period of the mountain limestone, and probably beyond it, if they be not now in existence. They appear, in his opinion, like the corals of Devon, to have been subject to repeated mineral accidents, and to have been locally destroyed in groups, not universally effaced in species. To guard himself, however, from misconstruction, Mr. Williams adds, he believes entirely in the extinction of genera and species; but at very distinct epochs, and in far thicker and more extended groups of strata than is imagined; and that consequently the identification of strata must be regulated by a per-centage test similar to that applied by Mr. Lyell to the tertiary series. Lastly, he protests against the determination of the age of the Devonshire formations by reference to the structure of a foreign district.

PROCEEDINGS AT THE FRIDAY-EVENING MEETINGS OF THE ROYAL INSTITUTION.

May 1.-Mr. Griffiths on the sources and uses of sulphuric acid. May 8. Mr. Faraday on the origin of electricity in the Voltaic pile. May 15. Mr. Macilwain on respiration and its relation to animal temperature.

May 22. Mr. Brande on white lead.

May 29.-Mr. Brockedon on some new applications of caoutchouc. June 5.-Rev. Dr. Scoresby on magnetism.

June 12.-Mr. Carpmael on the manufacture of wire cards.

I

[75]

LETTER TO PROF. LIEBIG ON THE THEORY OF SUBSTITU

SIR,

TIONS*.

HASTEN to communicate to you one of the most brilliant facts of organic chemistry. I have verified the theory of substitutions in an extremely remarkable and perfectly unexpected manner. It is only from the present time that we shall be able to appreciate the high value of this ingenious theory, and to foresee the immense discoveries it promises to realize. The discovery of chloracetic acid, and the constancy of the types in the chlorinated (chlorés) compounds derived from æther and the chloride of æthyle, have led me to experiments which I will now describe. I passed a current of chlorine through a solution of the acetate of manganese under the direct influence of solar light. After twenty-four hours I found in the liquid a superb crystallization of a yellow violet salt. The solution contained nothing further than this salt and hydrochloric acid. I analysed this salt: it was the chloracetate of the protoxide of manganese. Nothing extraordinary as yet; a simple substitution of the hydrogen of the acetic acid by an equal number of equivalents of chlorine, already known from the beautiful experiments on chlora. cetic acid. This salt, heated to 110° in a current of dry chlorine, was converted with disengagement of oxygen into a new compound of a gold yellow colour, the analysis of which had for its composition to the formula Mn Cl2 + C4 Cl 6 03. There was therefore a substitution of the oxygen of the base by chlorine, similar to what has been observed in a multitude of cases. The new substance dissolved in quite pure chloral with the aid of heat. I employed this liquid, unalterable by chlorine, in order to continue the treatment by means of this agent. I passed dry chlorine during four days, keeping the liquid constantly near its boiling point. During this time a white substance was constantly deposited, which, when attentively examined, proved to be the chloride of protochloride (?) of manganese. I cooled the liquor when all precipitation had ceased, and obtained a third body in small needles, silky and of greenish yellow colour; it was C4 Cl 10 O 3, or in other terms it was the acetate of manganese, in which all the hydrogen and the oxide of manganese had been replaced by chlorine. Its formula should be written Cl 2 Cl2 + C4Cl6O3. There were therefore six atoms of chlorine in the acid, the four other atoms representing the oxide of manganese. Just as hydrogen, so also manganese and oxygen may be replaced by chlorine, and nothing surprising will be found in this substitution. But this was not the end of this remarkable series of substitutions. On letting a new chlorine act on a solution of this substance in water, there was a disengagement of carbonic acid; and on cooling the liquid to + 2o, a yellowish mass, formed of small laminæ, was deposited, very much resembling the hydrate of

• From Liebig's Journal der Chemie und Pharmacie, vol. xxxiii. part 3.

Al

chlorine, and indeed it consisted of nothing further than chlorine and water. But in taking the density of its vapour I found that it was formed of twenty-four atoms of chlorine and of one atom of water. Here then is the most perfect substitution of all the elements of the acetate of manganese. The formula of the substance should be expressed by Cl2 Cl2 + C18 Cl 6 Cl 6 + Cl 9. though I am aware that in the bleaching action of chlorine there is a substitution of the hydrogen by the chlorine, and that the stuffs which are at present bleached in England, according to the law of substitutions, preserve their types*, I nevertheless believe that the substitution of carbon by chlorine, atom for atom, is a discovery belonging to me. I trust you will take a memorandum of this note in your valuable Journal, and believe, &c.,

types

SCHWINDERT.

ON THE FORMATION OF LAMPIC ACID.

Lampic acid, according to the experiments of Stas and Martius, is a mixture of formic and aldehyd acids. Mr. R. F. Marchand states that these acids vary in their respective proportions in the combination according to the temperature of the platina wire generating the acid, and that they may be obtained in a constant proportion, which may be nearly accurately determined when the experi. ment is made with alcohol or æther. When alcohol or æther is dropped upon a red-hot platina dish, the peculiar phænomenon is instantly produced; the liquid runs about the red-hot metallic surface without quickly evaporating, and forms the known figures which have been described by Bættcher. The vapour may be collected by putting a tubulated glass retort with the bottom off over the platina dish. By pouring fresh liquid through the tube a considerable quantity may be obtained in a short time. Upon examination it is easily ascertained that it is no longer alcohol, but possesses all the properties of lampic acid. The composition, or rather the mixture of the two ingredients, varies according to the temperature of the platina dish, in the same manner as that produced by platina wire. In order to ascertain whether the effect was peculiar to platina, Mr. Le Marchand tried glass, porcelain, polished copper and iron dishes; these also produced the same effects. They must, however, be polished and not present any rough surfaces; in the latter case the peculiar effect was not produced: it is also not produced when sand or glass is strewed over the platina dish.

The temperature to which the alcohol rises varies (as is the case with water) according to the heat of the dish and to the size of the drop. With water Mr. Le Marchand found it very accurately beginning at 180°, increasing to 204°, and then to 212o Fahr.: arrived at this point, the experiment is over, by the boiling of the water. The

en

* I have just learnt that there are already in the shops of London stuffs in spun chlorine (étoffes chlore filé), lé), much in request, and preferred to everything for night-caps, drawers, &c. † [Schwinder we presume means Hoaxer."-EDIT.]

same takes place with regard to alcohol; the temperature, beginning at 140°, rises at last to the boiling point of the liquid. When this takes place, the greater part of the alcohol burns; but before the burning commences, light blue flames are visible, which Dæbereiner also observed upon the vaporization of æther dropped on hot platina. Mr. R. F. Marchand wishes to guard against the inference that might be drawn from this experiment, that he considered that the liquids used were decomposed. The formation of lampic acid is based upon the fact, that the undecomposed vapour of alcohol passing within a certain distance, immediately over the hot metallic surface, is oxidated, which is also the case with platina wire. If the vapour were in actual contact with the metallic surface it would inflame.

Both experiments are a confirmation of Buff's explanation of the repulsion in Poggendorff's Annals, xxi., which is so full and satisfactory that it is unnecessary to look for any further elucidation.Journal für Pratische Chemie, 1840. No. 1.

ANALYSIS OF THE ASHES OF THE Salsola Tragus.

M. Guibourt has analysed the ashes of this plant from the neighbourhood of Cherbourg. He found that it consisted, independently of some silica, of

M. Guibourt observes, that it is curious that the salts of the ashes should contain potash as the alkali, and that it constitutes an exception to a maritime plant containing no soda. - Journ. de Chim. Med. Mars, 1840.

UNCOMBINED HYPOSULPHUROUS ACID.

M. Langlois, professor of chemistry at Strasburg, has succeeded in isolating hyposulphurous acid; he obtained it perfectly pure by decomposing hyposulphate of potash, with oxichloric acid, which forms an insoluble salt with potash.

The acid thus obtained is liquid, colourless, and of a slightly syrupy consistence. A period arrives when its density cannot be increased without partially decomposing it. Its taste is strongly acid and bitter; it does not appear to be very caustic. When exposed to the air, it attracts moisture, when heated in a glass tube to 176o Fahr., and there are produced a deposit of sulphur and sulphurous acid gas. It does not render the solutions of the salts of lime and strontia turbid. It produces no effect upon the solutions of the salts of iron, zinc, or copper; but with the salts of lead it yields a white precipitate which becomes black when heated. In the solution of nitrate of silver it forms at first a yellowish preci