vated, has less for its object to invent, as formerly, systems respecting the states through which the globe has passed, than to describe. exactly its actual state, and the relative position of the minerals which constitute its surface. It is known that in this point of view these masses have been divided into primitive, or those which exhibit no traces of organized beings, and which are considered as anterior to the existence of animals; and into secondary, which are all more or less filled with the remains of these bodies, and which consequently must have been formed after the existence of animals. These masses are, besides, generally different in their nature, and in the substances of which they are composed. It was even long believed that these bodies succeeded each other in a very regular manner, so that none of those deposited before the existence of organized beings were deposited afterwards, and vice versa.

But this was a premature assertion, which has been overturned by more observations. It has been observed that among these two kinds of deposites there exist mixtures, so that ancient formations are reproduced after more modern rocks have shown themselves; and some organized bodies are covered by masses of the same nature as those which were believed to have ceased to be deposited after the appearance of animals upon the globe. These monuments of the passage from one state of things to another have been called transition formations.

It is not always easy to recognise them for such; and M. Brochant, in a memoir published some time ago, required all his sagacity to assign to this intermediate class the greatest part of the rocks in the valley of Tarentaise; especially as at that time certain shells had not been discovered, whose existence in these rocks has confirmed, in the most flattering manner, the conjectures and reasonings of this skilful geologist.

He has since extended this kind of research, and has, during the present year, directed them principally to the old beds of gypsum, found in abundance in certain parts of the Alps, enormous masses of which must be perceived by all the travellers who pass over Mount Cenis. After describing, with the utmost exactness, all the circumstances relative to their position, and after having frequently gone round the mountains on the sides of which they appear, the author shows that their situation and their nature correspond with those of transition rocks, and proves that they must be arranged in that class.

The primitive formations themselves are not always easily characterized. The irregularity of their position, the immense space through which it is sometimes necessary to trace them, and the many variations in their composition, present great difficulties. Thus M. Brochant has ascertained, by long journeys and fatiguing examinations, that the high points of the Alps, from Mount Cenis to St. Gothard, and particularly Mont Blanc, are not, as has been generally believed, granite properly so called, but belong to a variety more crystalline, and more abounding in felspar, of a talky

and felspathic rock, which predominates in a very considerable proportion of the Alps, and which often contains metallic minerals in beds. He satisfied himself, at the same time, that a true granite formation exists on the south side of the chain; and from analogy he considers it as very probable that this granitic formation supports the talky rock. From which he concludes that the high summits of the Alps are not the portion relatively most ancient of these mountains. We gave an account at the time of a very analogous arrangementdiscovered in the Pyrenees by M. Ramond.

We ought always to remark that the primordiality_of_granite among known rocks is subject to exceptions. M. Von Buch ascertained that in Norway granites evidently characterized as such lie over rocks considered as more modern, and even over rocks containing petrifactions. This has been observed likewise in Saxony and in the Caucasus.

M. de Bonnard, Engineer of Mines in France, who, by a singularity honourable for us, has given to geology the first complete description of the Ertzgebirge, of that province of Saxony, which is in some measure the native country of geology. M. de Bonnard has endeavoured in that work to determine the places where the granite is below the other formations, and those in which it lies over any one. It cannot be doubted, from his examination, that the granite of Dohna is in this latter case, as had been announced by Saxon observers; but in other places, and especially near Freyberg, granite was too hastily concluded to be superior, from some irregularities in the form of the masses, the jutting portions of which frequently make their way through the rocks that cover them. It appears, likewise, that the chain which separates Saxony from Bohemia has likewise granite on its south side.

This memoir of M. de Bonnard contains many other precious details on the nature and position of the formations in the celebrated province which he has studied, and likewise on the rich metallic veins which traverse it in all directions, and on which the industry of the miners has been so long employed. In these respects it is equally interesting for geology and for the art of working mines.

M. Heron de Villefosse, at present a free associate of the Academy, has rendered an essential service to the same art by his work, entitled, De la Richesse Minerale. The first volume, which had for its object the administration of mines, was printed in 1810, and has been long known and esteemed. The second, in which he treats of the working of mines, has been presented in manuscript to the Academy. To the directions derived from the numerous sciences which furnish the theory, the author has added an immense number of facts collected in his travels, and in the exercise of his functions; so that the precepts are supported by examples, which have nothing imaginary, but are all realized in some place or other. A magnificent atlas exhibits to the eye all of these examples that can be represented. He gives geological maps of the Hartz

and of Saxony, the countries most celebrated for the antiquity of their mines; plans and sections of all the positions of the ore in the earth, and likewise of the different methods of working it, and every kind of machine employed for that purpose. Almost the whole of these materials are new, and have been collected on the spot by the author. The great utility of such a work, for a country in which the art of which it treats is still in its infancy, cannot be doubted.

The discovery, so important to geology, made by MM. Brongniart and Cuvier, of certain beds which contain only land and fresh water shells, and which of consequence cannot have been formed in the sea, like other beds containing shells, has excited numerous researches all over Europe. We gave an account at the time of those of MM. Marcel de Serres and Daudebart de Ferussac on fresh water beds in different parts of France, Spain, and Germany. Similar and very extensive discoveries have been made in England. This year M. Beudant, Professor at Marseilles, has considered this matter under a new point of view. As we find in some places fresh water shells mixed with sea shells, he endeavoured to discover by experiment how far the molusca of fresh water can be habituated to sea water, and vice versa. He found that all these animals die immediately if we suddenly change their place of abode; but that if we gradually increase the proportion of salt in the water for the one set, and diminish it for the other set, we can in general accustom them to live in a water which is not natural to them. There are some species, however, which resist these attempts, and which cannot bear any alteration in the quality of the water which they inhabit.

Nature pointed out these results beforehand. Certain oysters, certain cerites, the common muscle, proceed pretty high up in rivers; and we see some limneas in places where the water is a good deal mixed with sea water.

M. Marcel de Serres has continued his former researches on fresh water beds, of which we gave an account in our analysis for 1813. He has directed his principal attention this year to a formation of this kind, which he considers as newer than all the others, and which he discovered in seven different places in the environs of Montpellier. His observations are in some measure connected with those of M. Beudant. He distinguishes the species in the neighbourhood of Montpellier into those that do not appear capable of living except in fresh water; those which can exist in brackish water, of which the maximum is 2.75°; and those to which sea water appears necessary. He explains in this way some very rare

mixtures of the remains of these animals.

The formation which he describes is composed in some measure of two beds containing different shells. The upper one contains land shells at the same time with aquatic shells. The new forma tion is laid upon the surface of different formations, and chiefly

upon the sides of hills or platforms. We see there many land shells and vegetable impressions perfectly similar to the species living at present upon the same soil.

In proportion as we advance in Europe in geological observations, there are zealous individuals who apply them to remote countries, and who find nature faithful to the same laws.

We have spoken several times of the immense labours of Humboldt on the structure and elevation of the mountains of the two Americas. This philosophic traveller appears to have given a prelude to labours no less important by a general view of the results obtained in India respecting the height of different peaks of that immense chain known to the ancients by the name of Imaus, and where the Hindoos have placed the principal facts of their mythology.

From the trigonometrical measurements of Mr. Webb, an English engineer, four of these peaks are more elevated than Chimborasso; and one of them, the highest mountain at present known on the globe, is 4013 toises or 7821 metres in height, or according to other calculations 4201 toises, or 8187 metres.

M. de Humboldt in this memoir has made a happy use of the laws of vegetable geography, to supply information respecting the height of certain platforms which it has not been possible hitherto to ascertain directly. When such or such a plant is cultivated in a place he determines according to the latitude what height the platform in which the plant occurs cannot exceed. This will be a curious subject of verification for travellers, who, from the numerous relations established with them, will now go in greater numbers to visit these valleys and these mountains of Imaus, Thibet, Boutan, and Nepaul, countries probably the most interesting of all for the history of mankind, since every thing announces that it was from them that our race originally descended.

In a more limited space, M. Moreau de Jonnés, named lately a correspondent of the Academy, has not failed to make useful observations. He has presented to the Academy a geological map part of Martinique, in which the height of the different mountains is marked with great care, especially of the extinct volcano which seems to have produced most of those inequalities.

The author has extended his researches to the geology of a great part of the Antilles. Volcanic peaks occupy the elevated centres of these islands, and are called mornes. The beds of lava which have flowed from them are called barres, and the plains formed at their lower parts are distinguished by the appellation of plainiers.

Islands in which only one peak and a single system of eruptions occur, such as Saba, Nieves, St. Vincent, are smaller, and less important for agriculture. They have no good ports, because the harbours are merely the plains left between two or more systems, such as we see at Guadaloupe, Martinique, Dominica, St. Lucie, Grenada, &c. Martinique in particular seems to owe its origin to six volcanoes, and shows at present six peaks, to which the whole of it may be referred.

VOL. X. N° II.

K

M. de Jonnés gives us the exact topography and mineralogy of one of these; namely, Mount Pelée. He considers this volcanic nature as so general that he conceives it serves as a base to the whole Antilles, which exhibit superficially only lime-stone obviously containing shells, such as La Barbade and the larger portion of Guadaloupe. Guadaloupe properly so called is formed of four systems of eruption, one of which, the Soufriere, still retains some activity. M. de Jonnés likewise gives a description of it in a general statistical account of this island.

(To be continued,)

ARTICLE XIII.

SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

I. A Descending Spout on Land. By Luke Howard, Esq. On the 27th of the sixth month, at about seven in the evening, there occurred in our neighbourhood an undoubted exhibition of that rare spectacle (to observers on land)—the water-spout. I shall give the observations of two of our workmen at the Laboratory who saw it from Stratford, passing on their N horizon from NW to NE. I was absent myself in the West of England; but my friend John Gibson witnessed the latter part of the phenomenon.

The clouds had been exceedingly dark and threatening, and there had been thunder and rain in that direction; but at the time of the observation a clear sky was discernible beneath the clouds. From a dense cloud, the base of which might be at an elevation of 20°, there issued suddenly a descending cone, which one of the observers compared to a steeple inverted: this returned back to the cloud: a second and a third followed, one of which came lower, with a considerable perpendicular oscillation, and at length opened out below; and a straight column, which he compared to a dart, proceeded from its enlarged extremity to the earth, being visible also as a denser body pretty far up into the cloud. In a little time this cone also, losing its appendage, was drawn up again, and another or two, similar to the first mentioned, succeeding, closed the train of appearances, the whole having lasted about 15 minutes.

The course of this spout appears to have been over the country about Hampstead. In a communication, by another observer, to the Philanthropic Gazette, a person states himself to have been overtaken by it on Hampstead Heath, and to have been drenched by a fall of rain in very unusual torrents during its short passage. He conceived the spout to touch the top of the tree under which he had retired for shelter. The denser column seen by the observer at Stratford to proceed from the cloud admits of an explanation