when arsenite of potash or soda is mixed with a solution of any salt of copper, and a caustic alkali is added to it. It also takes place on mixing arsenite of potash or soda with hydrated oxide of copper, and then adding a caustic alkali; the change is very slow with heated oxide of copper. Upon examination of the precipitate after washing the following action takes place. Diluted sulphuric acid is coloured blue, and metallic copper is left; muriatic acid added in a small quantity changes the precipitate into a white powder, a larger quantity gives a brown solution; from which it follows that the precipitate is a suboxide of copper; this is confirmed by the experiments which follow. The reduction of the oxide of copper can only be attributed to the effect of the arsenious acid, which it is to be observed is converted into arsenic acid. 100 parts of arsenious acid, taking 16-1 parts of oxygen for its conversion into arsenic acid will therefore convert 159.6 of oxide copper into suboxide. In order to ascertain whether the reduction of the oxide of copper by the addition of the ingredients in this proportion would also result, as well as by the employment of arsenite of copper in which a larger quantity of arsenious acid was present, the following experiments were made: 1.6 gramme oxide of copper were dissolved in very dilute sulphuric, and 1 grm. of arsenious acid was dissolved in a solution of 10 grms. of caustic soda of specific gravity 1-20; the solutions were mixed together cold, and 20 grms. caustic alkali were added; the mixture was placed in a warm situation and often stirred; the colour soon changed and the precipitate completely formed. The solution was poured off, and the suboxide copper was washed with warm water and separated. The solution was neutralized by nitric acid; sulphate of copper gave a blue precipitate, and nitrate of silver a reddish brown precipitate, indicating the presence of arsenic acid. The washed precipitate mixed with boiled water acidulated by sulphuric acid changed immediately to brown flakes of metallic copper; the supernatant liquid was poured off, and the copper well washed with boiling water, collected and weighed; it weighed 0.62 gram. One half of 1.6 gramme of oxide of copper will give 0.638 metallic copper. The result of the foregoing experiment agrees nearly with this; it may be considered therefore that all the oxide of copper is reduced by arsenious acid to the state of suboxide. If this experiment were repeated by taking double the quantity of arsenious acid the same result would take place, and the oxide of copper would be only reduced to the state of suboxide. When caustic ammonia is used, the oxide of copper is only partially converted into suboxide. The solution remains perceptibly blue, and only becomes colourless upon the addition of a caustic alkali. If the blue ammoniacal solution is supersaturated by sulphuric acid, metallic copper is precipitated. The carbonated alkalies occasion no perceptible reduction of oxide of copper, which is also the case with caustic lime. Upon considering the reducing power of arsenious acid on oxide cimens of Axinus obscurus, and an Avicula, which will be noticed hereafter. At Bedford the magnesian limestone reappears under a form very similar to that at Collyhurst, but has been far more extensively exposed. It has for some time been quarried for burning, but at present the pit is filled with water, so that the fine section there presented from necessity cannot now be examined. As at Collyhurst, it consists of a series of red clays, with thin beds of limestone. The limestones are in numerous thin seams, rarely more than twelve inches in thickness. Towards the upper part they become still thinner, varying generally from one to four inches, and not forming continuous seams, but layers of flattened concretions, on the surface of which are found abundance of fossils. These limestones are variable in colour; the lower and thicker seams are of a greenish yellow colour, and the thinner ones more tinged with the red substance which has given the colour to the separating marles. SECT. III. Fossil Remains. The fossils of the magnesian limestone are neither numerous nor of peculiar interest; they chiefly consist of Axinus obscurus, Avicula, Crassina?, Trochus, and several varieties of minute turbinated shells, probably species of Turbo. The Axinus obscurus of Collyhurst differs only from those of Bedford and Yorkshire in having a regular series of concentric striæ on its external surface. These I have observed in impressions of some from the above places; but neither the granular limestone of Bedford, nor the calcareous shelly marle of Yorkshire, is so well calculated to preserve the delicate characters of the shells as the fine clay of Collyhurst. The Axinus is found in every stage of growth, and at both localities, with the exception of one single specimen from Bedford, consists entirely of single valves. From this it would appear that the shells had been gradually covered up, the ligaments being destroyed before they were buried and protected from decomposition and disunion of the valves. I am uncertain whether the Avicula be an undescribed spesies or not, but rather suppose it is. It approaches closely to Avicula socialis of Sowerby, which has induced some to consider the stratum as identical with the muschelkalk. I believe Professor Phillips is of opinion that the species is undescribed. The Trochus, which is a small and beautifully granulated one, as well as the minute turbinated shells, are certainly new, although some of them may be referred to by Professor Sedgwick, in his paper on the magnesian limestone of Yorkshire, without either figure or description. Two or three smaller bivalve shells occur, one of which, I believe, is Crassina, but as they are only casts, the species cannot easily be determined. The most important fossil is the Axinus, as from its extreme abundance in the magnesian limestone of Yorkshire it formed a ready means of identification. From this it will be seen that the magnesian limestone of the neighbourhood of Manchester is an unimportant bed compared with that of many other districts. The German zechstein and kupferschiefer have their remains of the Monitor and Palæothrissum, together with the peculiar impressions of Fucoids. The limestones of Durham and Northumberland have their Zoophyta and Radiaria, with numerous Mollusca and remains of fish. In Yorkshire are thick ranges of a yellow lamellar limestone, so well exhibited on the line of the Leeds and Selby Railway, literally teeming with beautiful specimens of Axinus; and here we have only a few unimportant beds of limestone, almost lost amongst the clays in which they occur, and only exhibiting a few casts of fossils, of which but one or two (the specific characters of which are so striking as not to be mistaken,) can be distinctly recognised. We will now examine the series of limestones, which as a means of local distinction we have called the (SECT. IV.) Ardwick Limestones. This provincial name has been given to the series of strata from the pits where they are chiefly worked being situated near the township of Ardwick. In this neighbourhood they are only exposed at the surface in the bed of the river Medlock, near Ancoats, but on the elevated ground above the river they are worked in several pits on a similar plan to the_collieries. These are now the property of Brocklehurst, Esq., and are under the management of Mr. F. Mellor, whose practical information and readiness to afford us every opportunity of examining the sections exposed in the different pits have been of the greatest importance to us. The following is an average section of the general appearances of the strata at the above pits, in a descending order: Limestone Ft. In. 4 0 Coloured red and blue clay, by the miners called " clunch" 6 0 60 60 0 3 3 0 5 0 2 0 necessary to be kept in view in order to obtain a correct analysis.— Poggendorff's Annals, 1836, No. 2. NOTICE OF THE LIFE AND CONTRIBUTIONS TO SCIENCE OF THE LATE M. NOBILI. The following notice of the scientific labours of M. Nobili, from the pen of Professor A. de la Rive, is translated from an article in the Bibliothèque Universelle. "It is with a feeling of the deepest grief that we announce the loss which science has recently experienced in the person of the Chevalier Leopold Nobili of Reggio. This distinguished natural philosopher died at Florence, on the 5th [17th?] of August 1835, at an age which gave the hope of a still longer continuance of his life: it appears that he sank under an affection of the chest. This loss, felt by all the learned world, is especially so by the editors of the Bibliothèque Universelle, to which M. Nobili was in the habit of consigning his important researches. Our journal has had the advantage of making known the first labours of the learned Italian, and of publishing thenceforward successively all the others. We therefore believe that we obey a sacred duty, and discharge the debt of a very natural gratitude, in endeavouring to recall in a few words the principal services which M. Nobili has rendered to science. "After having occupied himself with investigations respecting magnetism and light, purely theoretical, M. Nobili began in 1825 to devote himself to experimental researches. He commenced by inventing the galvanometer with two needles, which has since rendered such great services to experimental philosophy, and which has been generally adopted; its description will be found in the Bibliothèque Universelle, vol. xxix. p. 119. More recently, he added to this first invention that of the comparative galvanometer. But the series of investigations which in an especial manner made M. Nobili known to the learned world, was that relative to the colours developed upon metallic plates acting as poles in the electro-chemical decomposition of different solutions. The discovery of this brilliant phænomenon, the study of all the circumstances which accompany and modify the production of these coloured rings, were the object of two important memoirs, which, inserted at first in vols. xxxiii. and xxxiv. of the Bibl. Univ., were afterwards republished in most of the scientific journals. "It was while pursuing the examination of this subject, that M. Nobili succeeded in demonstrating the cause of the electro-chemical motions of mercury, (Bibl. Univ. vol. xxxv. p. 161,) and in discovering in the de-formation which the coloured appearances undergo in certain cases, the existence of a reciprocal action exerted by electrical currents, and analogous to the interference of luminous rays. (Bibl. Univ. vol. xxxvi. p. 3.) Some years later, he resumed the questions which related to the form and the production of these electro-chemical appearances, and succeeded in employing them as a valuable criterion to follow the elementary electrical currents in their progress, Three of the limestones are worked at Ardwick for the lime, viz. the "Four-Feet Mine," the "Yard Mine," and the main "Three-Yards Mine." There seems to be little difference between the qualities of these, their chemical constitution as well as general appearance being very similar. or Although I have given the average thickness of the limestones in the section, their exact thickness cannot always be estimated, owing to their being divided into layers with irregular seams of clunch. These interposing clays are not much liked by the miners, being unfavourable to their process of blasting, by diminishing the extent of the fall. This clunch, which forms an important feature in the vicinity of the limestones, consists of a dark brown clay, irregu larly tinged with a bluish green substance. It is found in connexion with all the layers, and is often of considerable thickness. SECT. V. Mineralogical Character of the Limestones. The most striking character of the whole of these limestones is the singular conglomerate appearance they present. This is more or less visible in all the strata, but more especially in the first, or Four-Feet Mine. A seam of variable thickness, generally about ten inches, passes along the lower part of this limestone, possessing the conglomerate character in so striking a degree that the miners can always recognise it where it appears, although it is sometimes interrupted; they know it by the name of Maxfield, a corruption of Macclesfield: the name has no meaning in it, except from a local circumstance of no importance. The limestone is generally of a light gray colour, often tinged with red: where the mottled appearance presents itself, the matrix is of a darker red or gray, and the imbedded fragments of a lighter hue, the ordinary colour of the stone. All the limestones are liable to slight variations of colour, even in the different divisions of the same "mine," being sometimes of a dirty gray and sometimes of a reddish yellow. The lowest portion of the Yard Mine almost approaches to black. The shales and clays between the limestones vary so much that a detailed description of them would be difficult. They are found of every variety, from a hard sandstone to a finegrained strong clay or marl, which latter sometimes contains organic remains, as above the " Four-Feet" seain on the bank of the Medlock, where it contains an Unio abundantly, and about sixty yards above the main or Three-Yards seam it is |