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a permanent or in a variable communication between the interior and the exterior of our planet.

The pressure of elastic vapour forces the melted substances upwards through deep fissures while they are undergoing oxida tion; volcanoes, if I may so speak, are intermitting springs of the earth; the liquid mixtures of metals, alkalies, and earths, which on cooling become currents of lava, flow quietly when they are raised, and find a vent. The ancients imagined, according to Plato's Phædon, that all volcanic currents of fire flowed, in a similar way, from the Periphlegeton.

It may be permitted me, perhaps, to add to these considerations one which is still more hazardous. In this interior heat of the earth, indicated by experiments with the thermometer, and by observations on volcanoes, the cause, perhaps, may be found, of one of the most wonderful phænomena which the examination of fossils presents to us. Tropical forms of animals, arboriform ferns, palms, and bamboo-like plants, lie interred in the cold north. The primitive world every where shows a distribution of organic forms at variance with the then existing nature of the climate. In order to solve this important problem, several hypotheses have been invented; as the neighbourhood of a comet, the altered inclination of the ecliptic, the increased intensity of the solar light. Neither of these has been sufficient to satisfy at once the astronomer, the natural philosopher, and the geognost. For my part, I leave the axis of the earth unaltered, as well as the light of the solar disc, by the spots on which, a celebrated astronomer has explained both the ferti lity and the unfruitfulness of the fields; but I believe, that in every planet, independently of its relation to a central body, and of its astronomical situation, various causes exist of the production of heat; oxidation, precipitation, and a change in the capacity of bodies; by increase of electromagnetic charge, by the opening of a communication between the interior and the exterior part of the earth.

Where the deeply cleft crust of the earth in the primitive world radiated heat from its fissures, whole countries, perhaps, could produce for centuries, palms and arborescent ferns, and sustain all the animals of the torrid zone. According to this view, to which I have already alluded in a work just published, "Essai Géognostique sur le Gissement des Roches dans les deux Hemispheres," the temperature of volcanoes would be that of the interior of the earth itself, and the same cause which now occasions such dreadful destruction, would once have occasioned, on the newly oxidated crust of the earth, upon the deeply cleft strata of rocks, the most luxuriant growth of plants in every

zone.

Even if any one should be inclined to suppose, in order to explain the marvellous distribution of tropical forms in their

ancient graves, that shaggy animals of the elephant tribe now imbedded in icebergs, were once peculiar to a northern climate, and that similar forms belonging to the same primary types, like lions and lynxes, could live in very different climates, such an explanation could not, however, be extended to the products of vegetation. For reasons which the physiology of plants explains, palms, and arboriform monocotyledones cannot sustain the northern cold, and in the geological problem we here speak of, it seems difficult to me to separate plants and animals. The same explanation must be applied to both.

Towards the end of this paper, I have combined uncertain hypothetical suppositions with facts collected from the most different parts of the world The philosophical knowledge of nature rises above a mere description of nature. It does not consist in a sterile aggregation of isolated observations. It may sometimes be allowed, therefore, to the curious and ever-active mind of man, to look back upon the past, to imagine what cannot be clearly known, and to amuse himself with the ancient, and, under many forms, returning mysteries of geogony.

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ARTICLE VIII.

Observations on Napthaline, with an Account of the Process by which it is obtained, and of the Mode of crystallizing it. By Mr. F. C. Chamberlain, Agent to the Chartered Gas Com

pany.

SIR,

(To the Editor of the Annals of Philosophy.)

For the purpose of procuring napthaline, the coal tar formed during the preparation of carburetted hydrogen gas is to be submitted to distillation. When a fourth part of the product intended to be obtained has been distilled, it is found to consist of a volatile spirit, ammonia, and water, holding a portion of napthaline in solution; this can only be separated either by very long standing, or by another and very different kind of

distillation.

By continuing the operation, a dense oil is obtained, at the bottom of 'which napthaline may be observed; after this it increases gradually in quantity until about half the product is distilled; if the remaining half be received as it comes over in three separate vessels, it is found that the first portion does not contain a great quantity of napthaline; from the second, little or none is obtained, even by very long standing; but the third portion contains so much napthaline that the last few gallons

sometimes become actually solid, when it has been a few hours distilled. The quantity of napthaline usually obtained is probably about five pounds from 100 gallons of the coal tar; but if the distillation be hurried towards the middle or latter end of the operation, the quantity of napthaline is much increased: may not this happen from the conversion of the oil into napthaline by the increase of temperature? The last portion of napthaline obtained is mixed with a very large quantity of sulphur.

If sulphuric acid be added to coal tar, little or no napthaline is procured; the acid probably decomposes the napthaline, for it holds but a very small quantity of it in solution.

When spirit or oil of tar obtained in making pitch, is set aside, much napthaline separates from it in a few weeks; and this effect may be more quickly produced by artificial cold; but agitation or increase of temperature readily dissolves the portion so deposited.

The napthaline is deposited from the oil in the vessels which contain it, in a semi-crystalline state, and much resembling coral in appearance, excepting that it is greyish instead of being perfectly white; by keeping, it becomes of so very dark a brown colour as to be nearly black; when large masses of it are broken the structure is frequently crystalline at the centre.

The smell of napthaline is extremely powerful and peculiar; when melted and allowed to cool gradually, it presents cells which are intersected in every direction by beautifully white and shining plates.

The napthaline separated from oil which has been twice distilled, requires a much greater heat to sublime it than that found originally in the oil; the latter melts at about 120°, and begins immediately to sublime; but if sulphuric acid be triturated with it, it requires a greater heat even than the first mentioned for sublimation; and by this process, there is obtained a mass resembling a honeycomb in appearance, owing to the peculiar arrangement of the crystalline napthaline.

During the sublimation of napthaline, a fluid is obtained which is worthy of careful examination. At first its taste is sweet, and highly aromatic; it is afterwards pungent; and occasionally hydrocyanic acid may be obtained from it, and in pretty considerable quantity.

When napthaline is mixed with water, it rises in vapour with the water; in this way it is obtained in a state of greater purity than by sublimation, but the quantity procured is small. Napthaline is soluble in spirit of wine, and by evaporation crystals are obtained, but they are neither large nor perfect; nor when dissolved in oil of tar, can any distinct crystals be obtained; after trying various fluids for the purpose of procuring perfect crystals, I succeeded but with oil of turpentine.

When napthaline is added to the last mentioned fluid, its temperature sunk from 65° to 574°, and the best method of causing the solution to crystallize is the following: Dissolve as much napthaline in a quart of oil of turpentine as it is capable of taking up by agitation; then add about two ounces more napthaline, and dissolve it in the oil with the assistance of heat. Set the solution in a very cool place to crystallize; in this way long prismatic crystals terminated by pyramids will be procured. If the fluid poured off after the formation of these prismatic crystals remain in a cool place, large hexagonal plates may be obtained. To obtain a honeycomb mass, differing from that formed by sublimation only in the greater thickness of the partitions, pour off the fluid from the plates obtained as above, after they have been forming for at least 48 hours; set it aside to crystallize, and in a few days, the honeycomb mass will be procured.

It is very entertaining to watch the fluid when crystallization is commencing. Minute particles are seen passing from one part of the vessel to another; sometimes a crystal will be perceived to increase suddenly in size; it will then circulate through the whole of the fluid with great rapidity, and afterwards approaching another similar crystal, they will for some time mutually attract each other; but as soon as they come in contact, both are violently repelled to a considerable distance; after a time attraction recommences; they again approach each other, and are again repelled; the repulsive power lessening after every contact, they eventually unite.

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In this way several prismatic crystals may be observed undergoing alternate and mutual attraction and repulsion, and eventually forming the radii of a hexagon, which is by degrees com pleted, and becomes a regular hexagonal plate.

The action of nitric acid upon napthaline is peculiar; when they are triturated together, a butyraceous compound is formed, which smells exactly like new hay. If the acid be used in con siderable quantity, a great number of small spiculæ, which have the appearance of a salt, are seen floating in it. It might be supposed that they are crystals of nitrate of ammonia, but this is not the case, for they are nearly tasteless, and difficultly soluble; but their true nature I have not yet determined.

ARTICLE IX.

Astronomical Observations, 1823.
By Col. Beaufoy, FRS.

Bushey Heath, near Stanmore.

Latitude 51° 37′ 44.9" North. Longitude West in time 1′ 20.93".

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Clouds prevented the observation of the commencement; but the ending was made under

very favourable circumstances.

ARTICLE X.

ANALYSES OF Books.

1. The Elements of Experimental Chemistry. By William Henry, MD. FRS. &c. &c. The Ninth Edition, comprehending all the recent Discoveries; and illustrated with 10 Plates by Lowry, and several Engravings on Wood. In Two Volumes. 1823.

IN noticing the present edition of Dr. Henry's Elements of Chemistry, it is not my intention to enter minutely into a discussion of its merits: it is a work which has been so long and justly appreciated as to bid defiance to criticism, and render particular commendation superfluous. It would, however, I think, be unjust to the author and the public, not to depart a little from the usual course in thus announcing a new edition of an established work, on account of the improvements and numerous important addi tions with which it has been enriched.

With true philosophical caution, Dr. Henry has not been hasty in admitting more modern doctrines to displace those which were not only by him, but by the chemical world in general, received as true, until within a few years. In making this remark, I allude to Sir H. Davy's views of the nature of chlorine; and if the late edition of Dr. Henry's work was in any respect imperfect, it appeared to me to be in the uncertainty which pervaded it with respect to the nature of chlorine, and the consequent difficulty which must have attended the learner in acquiring settled opinions, when the teacher appeared undecided.

In the present edition this indecision is removed, and although the former opinion of the compound nature of chlorine may be

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