verer of iodine in the atmosphere, is continuing his researches on this subject. The general result of his latest observations leads him to conclude, that the nearer he approached the Alps the smaller was the quantity of iodine, and that in some districts, as Maurienne, this atmosphere contained no iodine.

GEOLOGY.

3. On the Internal Structure of Mountains. By B. Cotta. (Leonhard u. Bronn's Jahrb. f. Min. u.s.w. 1851, p. 181-2.) -In a letter to Dr K. C. v. Leonhard, the author states that in a short memoir on the Internal Structure of Mountains, lately published at Freiberg, he has attempted the physiology, as it were, of mountains, in shewing the different phases of their formation and destruction. The chief results arrived at are

1. The mountains did not suddenly arise, but were formed by degrees, sometimes during very long periods of time.

2. For their position and direction there are as yet no general laws positively known.

3. All true mountains are results of elevatory volcanic (plutonic) action.

4. The majority, however, in their present form, are at the same time the result of a later destructive process (the action of water), in very unequal degrees.

5. The mountain-elevations are to be distinguished as local, from the continental elevations of great tracts of land, which latter may be bare swellings, unless eruptive rocks find a local vent.

6. Horizontal forms of the mountains correspond in some degree to the grouping of the volcanoes, the single mountain masses (Massen-Gebirge) to the central volcanoes (Vulkan-Gruppen), the mountain chains to the lines of volcanoes (Vulkan-Reihen).

7. Of the origin of mountains the author distinguishes three principal kinds, and very many forms of combination, and stages of development and destruction. The three kinds of origin are

a. By the efflux and superficial accumulation of eruptive rocks ;

volcanic mountains.

b. By the elevation of existing hard portions of the earth's crust, caused by eruptive rocks penetrating upwards;-plutonic

mountains.

c. By lateral pressure, and, in consequence thereof, the folding of existing hard portions of the earth's crust.

8. Several of these kinds of development, however, sometimes occur in combination with one another.

9. The mountains originating in the elevation of the existing hard portions of the earth's crust, owing to the upward pressure and penetration of eruptive masses, exhibit the most manifold diversity of stages of destruction, whereby they fall into mountains with folded

strata (Falten-Gebirge), crystalline slate mountains, and central mass mountains of upper, middle, and lower section.

10. The mountains with folded strata of this sort, however, are not always distinguishable from those originating in lateral pressure. 11. Of especial importance in judging of the relative age of the

mountains-besides the distinction of elevated and non-elevated beds brought forward by E. de Beaumont-is the fixing of the mountain chains as lines of separation between deposits during determined periods; recognizable by dissimilar characters in the series of sedimentary formations on two or more sides.

12. The volcanic mountains are distinguished from the plutonic, consolidated within the earth, both by their external form and by their mineralogical conditions. The first form superficial, the second form subterranean, cones of eruption. The section of these last exhibits (for example) the so-frequently referred to granite-ellipsoids. Both, however, fill up also narrower fissures, in which they are then mostly crystallized somewhat otherwise than in the great principal masses.

4. On German Tertiary Formations. By F. Sandberger. (Leonhard u. Bronn's Jahrbuch f. Min. u.s.w. 1851, p. 177.) -Tertiary formations of the age of the Mayence Basin are widely distributed in Germany. That the Brown-coal formations of Westerwald and the Lower Rhine, as also that of the Vogelsberg, belong to this period, is easily proved by their fossil shells and plants. With regard to their Vertebrata, Von Meyer long since supplied the necessary proof. Moreover, the Brown-coal formations of Miesbach, in Upper Bavaria, contain Cyrena subarata, Bronn, Cerithium margaritaceum, and other characteristic forms of the Mayence Basin. The Vertebrata of the Molasse of Switzerland agree also with those of the last deposit; and in respect to North Bohemia, the elaborate work of Von Meyer and Reuss* affords also a similar result. The Mayence Basin is, moreover, the type of a whole series of such deposits, as is the London Basin with respect to the old tertiary clays of the Baltic plain.-Quarterly Journal of the Geological Society, vol. vii., No. 28, p. 118.

5. On an extensive Rock-Formation of Siliceous Polycystina from the Nicobar Islands. By Prof. Ehrenberg. (Berlin Monatsbericht, 1850, p. 476-478. Leonhard u. Bronn's Jahrbuch f. Min., u.s.w. 1850, p. 237.)-Hitherto, Barbadoes only has afforded rocks with Polycystina. The Nicobar Islands lie in nearly an equal latitude with it, but in the East, instead of the West Indies. They consist of syenitic and serpentinous porphyry or gabbro-rock with pyrites, but without any recent volcanic ejectments, on which, to the height of 2000', lie clays, marls, and calcareous sandstones, rich in Polycystina. The author has already obtained

*Palæontographica, II. 2.

from hence 100 species, which are partly identical with the 300 species from Barbadoes. The islands Car Nicobar and Comarta are especially remarkable in this respect, and on the latter exists a hill 300′ high, throughout which the Polycystina-clay occurs. A light meerschaum-like clay and shale (tripoli, polishing shale) found there and at other places is composed nearly altogether of these bodies, mixed with many Spongolithes. These clays are generally traversed by lignitiferous deposits, and by syenitic gravels.—Quarterly Journal of the Geological Society, vol. vii., No. 28, p. 118.

6. Mr J. B. Guimet's Process for the Manufacture of Artificial Ultramarine.-Previous to the year 1828, all the ultramarine in use was obtained from the Lapis Lazuli, a rare mineral procured from Siberia. A common ultramarine thus obtained, is, at the present time, sold at seven guineas per ounce, and the price of a genuine and very choice article, is upwards of twenty guineas per ounce. From its great costliness, the use of this pigment is confined entirely to the artist. Several analyses of ultramarine were undertaken with the view of finding out a method of making it artificially. These analyses shewed it to be a compound of silica, alumina, sulphur, soda; but the supposed colouring principle for some time evaded all attempts at its detection. At last, M. Guimet of Lyons, in the year 1828, aided by these analyses, and encouraged by the offer of a prize of 6000 francs from the Société d'Encouragement of Paris to the person who should succeed in the manufacture of artificial ultramarine, hit on the happy idea of giving up further search for the hidden colouring principle, and confined his attention to the combination of the several colourless ingredients which chemical analysis pointed out as the constituents of natural ultramarine. The result was the discovery of artificial ultramarine. M. Guimet kept his process a secret, selling his ultramarine at 42s. per pound. Gmelin, Persoz, and Robiquet afterwards discovered the process, and published the mode of preparing this pigment, since which time its manufacture has extended in Germany and in France, and has latterly been introduced into this. country.

Ultramarine appears to be a compound of silicate of alumina and silicate of soda, with sulphuret of sodium, and the colour is supposed to be due to the reaction of the last constituent upon the former two. It may be prepared, according to Gmelin, by rapidly igniting a mixture of equal parts of silica, carbonate of soda, and sulphur, first adding a sufficient quantity of a solution of soda to dissolve the silica. The result is a bluish-green mass, which, by ignition in contact with air, becomes blue. Ultramarine is now sold as low as fifteenpence per pound. It is applied to various purposes in the arts, such as paper-staining, the azurage, or blue tinting of writing papers, starch, ground white lead, &c., and has recently been applied to the printing of cotton goods. It has superseded

smalts in many industrial purposes; but as it is not an enamel colour, its employment is not applicable in the colouring of china and earthenware.-Pharmaceutical Journal and Transactions, vol. xi., No. v., p. 230.

MINERALOGY.

7. Exhibition of Statues and Gems in the Crystal Palace.-The nature of the articles exhibited depends as much upon the character of the building which is to receive them as it does upon their own individual character. In a building which admits the whole light of the sky, except where it is eclipsed by the beams of its carpentry, it would be impossible to make a favourable exhibition of pictures, while statues could be advantageously displayed. When an oil painting is illuminated from numerous points, or by broad beams of light, the varnished surface, thus rendered visible, destroys the finest touches of the artist, and removes the illusion which he had produced. In like manner, gems, such as the diamond, which derive their principal beauty from the prismatic spectra which they produce, lose all their charm when exhibited in a palace of crystal, while gems and precious stones, which derive all their beauty from their colour, are displayed to great advantage. The great Koh-i-noor, or Mountain of Light, the Durra-i-noor, or the Sea of Light, and the fine blue diamond of Mr Hope, have less effect, as now exhibited by daylight, than a piece of glass of the same size and tint would have, if exhibited in a private room with two or three windows. In the spectra produced by broad luminous spaces, all the colours are recombined into white light, and hence the disappointment which every person has experienced at the first sight of these singular gems. Were the same gems to be worn by a lady in a drawing-room, with numerous bright lights, their effect would astonish the company.* The fine coloured refractions of the diamond disappear also under other circumstances. When the diamonds are very small, and set closely together, the numerous prismatic spectra which they produce are mingled, and produce white light on the retina of the eye, and this diminution of colour increases with the number of lights. When small diamonds, however, are at a sufficient distance from each other, they are seen to the greatest advantage when the lights are sharp and numerous.

As the sight of rare precious stones must always be exceedingly interesting, because they are never seen in collections of minerals, and when in the possession of individuals can only be seen by their private friends, it would have been desirable to place all the diamonds (as the Koh-i-noor is, on Fridays and Saturdays), in a dark apartment, illuminated by numerous small and brilliant lights. Till this

itself.

Many intelligent persons mistook the hollow foil for the great diamond

was done with the Koh-i-noor, nobody had any idea of its purity and beauty, and, indeed, nobody till then could say that it was not a piece of glass.*-North British Review, No. xxx., p. 542.

ZOOLOGY.

8. Flying-Fish.—The common opinion that the motion of the Flying-fish through the air is nothing more than a vigorous leap, sanctioned as it is by many honoured names in science, I have long believed to be incorrect, having on several former occasions seen what appeared to me a distinct motion of the fins. To settle this point was one of the desiderata which I had particularly noted down on commencing this voyage; and the result has fully confirmed my belief. The observations as they occurred, I shall quote in the form in which they were recorded.

I

Nov. 20th.-Lat. 19° 24′ N., long. 41° 5′ W.-Many Flyingfishes appeared in the course of the day: the first we had observed. They were the silvery species commonly seen in the Atlantic, of middling size, with clear wings; probably Exocetus volitans. now feel certain that these fishes have power to change their direction when in the air; more than one, which I saw to-day, turned aside at nearly a right angle.

Nov. 22d.-Flying-fishes leap from the sea every few minutes; several made courses distinctly angular, and some, I am quite sure, rose and sunk in undulations. To confirm my own observations, I requested a gentleman on board to notice this point; and he was quite certain of both of these facts.

Nov. 24th.-I observed to-day a Flying-fish, after flying a short distance, suddenly turn downward, abruptly and perpendicularly, as if alarmed, and enter the water. The action exactly resembled that of a bird.

Nov. 25th. Several times I have observed in the flight of the Exocœtus, when near, an occasional fluttering of the pectorals. In general, these wing-fins appear notionless; but at the moment of rising to avoid the crest of a wave, there is a slight but rapid vibration of these organs, distinctly perceptible, if the fish be pretty close to the ship. I saw an Exocœtus to-day which was much larger than the species hitherto observed, with the pectorals wholly of a sooty black colour. Probably it is the Exocatus Noveboracensis of Dekay. The others are still rather numerous, but do not rise in flocks.

Nov. 27th. This morning multitudes of Flying-fishes rose, dis

* The introduction of ground glass globes into our apartments, however beautiful they may be as objects seen by the eye, destroy the beauty of all other objects. Silver and gold plate, and all other objects that derive their beauty from the reflected light, lose their polish, and have actually the same appearance as if their surface was ground. The coloured spectra, too, produced by the diamond and other precious stones, are all dimmed as if they were seen through ground glass.