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fire. On the human frame its effects are considerably felt; the lips and nostrils become sore and inflamed, and the throat parched, and other exceedingly uncomfortable sensations are excited; although it is generally said to give to wounds and ulcers a strong predisposition to heal. Its duration varies from two or three to seventeen or eighteen days; this may be considered as part of the finest season, which continues till the tornados again commence. It is not peculiar to this part alone, but prevails throughout the whole extent of tropical Africa.

The above description of the weather within the before-mentioned limits on the coast of Africa, although it appears to be divided, and governed by laws, with the most perfect regularity, is by no means to be considered as not subject to any variation for although a portion of the year is called the tornado season, tornados are not uncommon during the periodical rains, insomuch that in the neighbourhood of Sierra Leone, the end of September is frequently called the second tornado season.

REFLECTIONS ON VOLCANOS.

BY GAY LUSSAC.

Read before the Royal Academy of Sciences at Paris, May 19, 1823. Ann. de Chimie et de Phys. tom. xxii. p. 415.

BEFORE I offer to the public the following observations on Volcanos, a subject which has so long presented a wide field for hypothesis and conjecture, I ought to premise that I am not in possession of all the knowledge necessary for its full discussion, and that I shall only take a brief and partial view of it, confining myself to certain questions upon which chymistry may throw some light, and which do not absolutely demand an acquaintance with geology. The subject is however one of considerable difficulty, and one which gives me a claim on the indulgence of my readers.

Two hypotheses may be formed as to the cause which produces volcanic phenomena. According to one of these, the earth remains in a state of incandescence at a certain depth below the surface (a supposition strongly favoured by the observations which have been recently made on the progressive increase of temperature in mines;) and this heat is the chief agent in volcanic pheAccording to the second hypothesis, the principal cause of these phenomena is a very strong and as yet unneutralized affinity existing between certain substances, and capable of being called into action by fortuitous contact, producing a degree of heat sufficient to fuse the lavas and to raise them to the surface of the earth by means of the pressure of elastic fluids.

nomena.

According to either of these hypotheses, it is absolutely necessary that the volcanic furnaces should be fed by substances originally foreign to them, and which have been some how or other introduced into them.

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In fact, at those remote epochs which witnessed the great catastrophes of our globe, epochs at which the temperature of the earth must have been higher than it now is, the melted substances which it contained consequently more liquid, the resistance of its surface less, and the pressure exercised by elastic fluids greater, all that could be produced was produced: an equilibrium must have established itself, the agitated mass must have subsided into a state of repose which could no longer be troubled by intestine causes, and which can only now be disturbed by fresh contact between bodies accidentally brought together, and which were, perhaps, only added to the mass of the globe subsequently to the solidification of its surface.

Now the possibility of contact between bodies in the interior of the earth, the ascent of lava to a considerable height above its surface, ejections by explosion, and earthquakes, necessarily imply that those extraneous substances which penetrate into volcanic furnaces must be elastic fluids, or rather liquids capable of producing elastic fluids, either by means of heat which converts them into vapour, or by affinity which sets at liberty some gaseous elements. According to analogy, the only two substances capable of penetrating into the volcanic furnaces in volumes sufficiently large to feed them, are air and water, or the two together. Many geologists have assigned to the air an important office in volcanos; its oxygen according to them sustains their combustion: but a very simple observation will suffice to overthrow this opinion entirely.

How, indeed, is it possible for the air to penetrate into the volcanic furnaces when there exist a pressure acting from within towards the exteriors capable of raising liquid lava, a body three times as heavy as water, to the height of more than 1000 metres, as at Vesuvius, or even of more than 3000, as is the case in a great number of volcanos? A pressure of 1000 metres of lava, equivalent to a pressure of 3000 metres of water, or to that of about three hundred atmospheres, necessarily excludes the introduction of any air whatever into volcanos; and as this pressure exists for a long series of years, during which the volcanic phanomena continue in the utmost activity, it follows that the air can have no share whatever in their production.

It is moreover evident, that if the air had a free communication with the volcanic furnaces, the ascent of lava and earthquakes would be impossible.

If the air cannot be the cause of volcanic phænomena, it is probable, on the contrary, that water is a very important agent în them.

It can hardly be doubted that water does penetrate into volcanic furnaces. A great eruption is invariably followed by the escape of an enormous quantity of aqueous vapour, which, being condensed by the cold which prevails above the summits of vol

canos, falls again in abundant rains accompanied by terrific thunder, as was the case at the famous eruption of Vesuvius in 1794, which destroyed Torre del Greco. Aqueous vapours and hydrochloric gas have also frequently been observed in the daily ejections of volcanos. It is scarcely possible to conceive the formation of these in the interior of volcanos without the agency of water.

If we admit that water is one of the principal agents in volcanos, we must proceed to examine the real means by which it acts, upon either of the hypotheses we have just laid down concerning the heat of volcanic furnaces. If we suppose, according to the first hypothesis, that the earth continues in a state of incandescence, at a certain depth below its surface, it is impossible to conceive the existence of water at that depth; for the temperature of the earth having formerly been of necessity higher, its fluidity greater, and the thickness of its solid crust less than at the present time, the water must necessarily have disengaged itself from its interior and have risen to the surface.

If we wish therefore to give any air of probability to this hypothesis, and to maintain the importance of water as a principal agent in volcanos, we must assume that it penetrated from the surface downwards to the incandescent strata of the earth; but in order to come to this conclusion, we must suppose that it had a free communication with those strata, that it gradually acquired heat before it reached them, and that the vapour it produced com pressed by the weight of its whole liquid column, obtained a sufficient elastic force to elevate the lavas, to produce earthquakes, and to cause all the other terrible phænomena of volcanos.

The difficulties obviously involved in these suppositions, and to which many others might be added, render the hypothesis that the heat of volcanos is to be attributed to the state of incandescence of the earth at a certain depth below the surface, perfectly inadmissable. I must further remark that this incandescence is itself quite hypothetical; and that, not withstanding the observations on the increase of temperature in mines, I regard it as extremely doubtful.

(To be continued.)

Miscellaneous.

AMERICAN COLONIZATION SOCIETY.

Extracts from the First Report of the New-York Colonization Society. NEARLY seven years have elapsed since a Society was formed at Washington, for the purpose of " promoting and executing a plan for colonizing the free people of colour, residing in America, in Africa, or such other place as Congress should deem most expedient." As a preliminary step to the carrying of this plan into successful execution, it was deemed proper to send out agents to the coast

of Africa, to ascertain the most favourable site for the proposed colony, and at the same time to gather such general information as might facilitate the future operations of the Society. Messrs. Mills and Burgess were accordingly appointed upon this service in the year 1817; and the result of their labours and inquiries was such as to satisfy the Managers that the establishment of a colony on the west coast of Africa might be attempted, not merely with safety, but with every prospect of success. Having obtained this information, it was determined at once to commence their labours in this region of the globe; and measures were immediately adopted for sending out, with all possible speed, the first settlers in the proposed colony. A vessel, the Elizabeth, was accordingly chartered and dispatched to Africa, with about eighty coloured people, together with the two agents of the Society, and one of the government of the United States, appointed to superintend the reception of rescued slaves from on board the slaving ships. The vessel sailed from this port, and the spirit and alacrity with which our citizens came forward to furnish her with necessary supplies, exhibit a satisfactory proof that they are not insensible to the claims of this noble and benevolent enterprise.

The first location of the colonists, on their reaching Africa, proved, unfortunately, to be in every respect disadvantageous; and information soon reached the Managers of the death of the three agents, together with about twenty of the colonists. In consequence of these and other disasters, threatening their immediate and almost total destruction, the colonists, on the arrival of new agents from the United States, were removed to Sierra Leone, and placed under the protection of the British government. Here they remained until a proper situation could be procured for their settlement. Through the zeal and ability of Dr. Ayres, agent of the Society, and Lieutenant Stockton, of the United States Navy, this was accomplished. A tract of land at Cape Montserado,* was purchased from the native kings, which, according to the description given of it, combines every local advantage, situated on the banks of a large river," and with one of the best harbours between Gibraltar and the Cape of Good Hope." The colonists were soon after removed to this spot, and the first foundation of a settlement laid, whose benign influence, we trust, will be felt and acknowledged for ages to come, in the remotest regions of Africa.

It is unnecessary to dwell, in detail, upon the intermediate history of the colony. The annual Reports of the parent Institution contain the amplest information on this subject, and are filled with a recital of the most important incidents in relation to its origin and progress. To the lover of bold adventure, as well as

Cape Montserado, which is high land, is situated in about the fifth degree of north Latitude. Sierra Leone is in N. lat. 8° 30'. Mesurado is the name of the river and bay that wash the cape. · The cape is also sometimes called Mesurado.

to the philanthropist and the Christian, we recommend the perusal of these interesting documents. It is sufficient for our present purpose to state, that, notwithstanding the dangers and the difficulties necessarily attending the planting of an infant settlement on a remote and barbarous shore, the colony still exists and flourishes. According to the latest accounts, the number of settlers is about two hundred, under the superintendence of two agents, of acknowledged character and abilities. The misunderstanding, which at first existed between them and the natives, has been satisfactorily adjusted, and every thing seems propitious to the growth and perpetuity of the establishment.

Such is a brief sketch of what has been accomplished under the auspices of the parent Society. To aid in the execution of a plan, so magnificent in its design, and so benevolent in its object, this Auxiliary was formed. It has already existed for six years, and though less has been done by it than was either wished or expected by the friends of colonization, yet the Managers feel confident that its formation and continued existence have not been without their use. Although it has thus far contributed but little to the pecuniary resources of the Society, the Managers flatter themselves that it may have been the means of keeping alive, in this section of our country, a sympathy for the general object, which, it is hoped, will ere long pervade every portion of the community. Notwithstanding the open hostility of some, the skepticism of others, and the cold indifference of a still greater number, the Managers are proud to record their firm and unalterable conviction in favour of the great cause in which they are enlisted. They believe it to be a project, not merely practicable, but pregnant with the greatest blessings to humanity. To this country it offers the only possible means of gradually ridding ourselves of a mighty evil, and of obliterating the foulest stain upon our nation's honour. To those who emigrate, it offers an asylum in the land of their fathers, where they may stand forth in the character of men, and enjoy the rights and privileges of freemen. To Africa, it offers the suppression of the slave trade, while it presents in bold perspective the brightest prospects of future civilization and refinement. If this unfortunate portion of our globe is ever to be regenerated in its intellectual and moral character, there is no question that it will have to be the result of efforts foreign to itself. All history proves that no people were ever redeemed from ignorance and barbarism, except through the agency of a nation already civilized.

If such be the fact, how immensely does the establishment of this colony swell in interest, when viewed in its relations to Africa! It is no extravagant supposition, that, if success attends the present enterprise, colonies will ere long be found established in abundance along the coast of Africa, and that through them, civilization, science, and Christianity, will pour their blessings

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