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of earthquakes more dreadful still'. In one letter, moreover, he has mentioned some particulars which afford an excellent lesson to all who are fond of exploring Nature in her wonderful operations; teaching them not to form rash and premature conclusions from appearances only, but to proceed in their researches with patient and steady investigation. He has demonstrated, that many of the revolutions in the face of the globe have been effected by absolute chemical processes, carried on by Nature, on a more wonderful and extensive scale, than the puny efforts of human art.

The gulfs of Gaeta and Terracina (says Sir William) may, in the course of time, become another Campo Felice: for the rich and fertile plain so called, which extends from the bay of Naples to the Appenines, behind Caserta and Capua, has evidently been entirely formed by a succession of such volcanic eruptions. Vesuvius, the Solfaterra, and the high volcanic grounds, on the greater part of which the city of Naples is built, were once probably islands; and we may conceive the islands of Procita, Ischia, Ventotiene, Palmarole, Ponza, and Zannone, to be the outline of a new portion of land intended by Nature to be added to the neighbouring continent; and the Lipari islands (all of which are volcanic) may be looked upon in the same light, with respect to a future intended addition to the island of Sicily.

The more opportunities I have of examining this volcanic country, the more I am convinced of the truth of what I have already ventured to advance, which is, that volcanos should be considered

The dread volcano ministers to good;

Its smothered flames might undermine the world:
Loud Etnas fulminate in love to man.

2 Philos. Trans. vol. xxxvi. part 2, for 1786.

YOUNG.

in a creative rather than in a destructive light. Many new discoveries have been made of late years, particularly in the south seas, of islands which owe their birth to volcanic explosions; and some, indeed, where the volcanic fire still operates. I am inclined to believe, that upon further examination, most of the elevated islands, at a considerable distance from continents, would be found to have a volcanic origin; as the low and flat islands appear in general to have been formed of the spoils of sea productions, such as corals, madrepores, &c.

Those who have not had an opportunity of examining a volcanic country, as I have for more than twenty years, would little suspect, that many curious productions and combinations of lavas and tuffas1 were of a volcanic origin; especially when they have undergone various chemical operations of Nature, some of which have been capable of converting tuffas, lavas, and pumice-stone into the purest clay.

I have observed, that young observers in this branch of natural history have been too apt to fall into the dangerous error of limiting the order of Nature to their confined ideas: for example, should they suspect a mountain to have been a volcano, they immediately climb to the summit to seek for the crater; and if they neither find one, nor any signs of pumice-stone, directly conclude such a mountain not to be volcanic: whereas, only suppose Mount Etna to have ceased erupting for many ages, and that half of its conical part should have mouldered away by time (which would naturally be the consequence) and the harder parts remain in points, forming an immense circuit of mountains (tna extending its

The tuffa, or tufa, is a stone formed of volcanic ashes, concreted with various other species of stone, in which argil predominates. It is harder than marble, but still porous and spongy.

basis more than 150 miles); such an observer as I have just mentioned would certainly not find a crater on the top of any of these mountains; and his ideas would be too limited to conceive, that this whole range of mountains were only part of what once constituted a complete cone and crater of a volcano. It cannot be too strongly recommended to observers in this, as well as in every other branch of natural history, not to be over hasty in their decisions; not to attribute every production they meet with to a single operation of Nature, when perhaps it has undergone various, of which I have given examples in the island which is the principal subject of this letter'. That which was one day in a calcareous state, and formed by an insect in the sea, becomes vitrified in another, by the action of the volcanic fire, and the addition of some natural ingredients, such as sea salts and weeds, and is again transformed to a pure clay, by another curious process of Nature. The naturalist may indeed decide as to the present quality of any natural production; but it would be presumptuous in him to decide as to its former states. As far as I can judge in this curious country, active Nature seems to be constantly employed in composing, decomposing, and recomposing; but surely for all wise and benevolent purposes, though on a scale, perhaps, too great and extensive for our limited comprehension.'

1 The island of Ponza.

No. LVI.

ON THE ART OF NAVIGATION.

Inventâ secuit primus qui nave profundum,
Et rudibus remis sollicitavit aquas;
Tranquillis primus trepidus se credidit undis,
Littora securo tramite summa legens :
Mox longos tentare sinus, et linquere terras,
Et leni coepit pandere vela noto:

Ast ubi paulatim præceps audacia crevit,
Cordaque languentum dedicere metum ;
Jam vagus irrupit pelago, cœlumque secutus,
Ægeas hyemes, Ioniasque domat.

CLAUDIAN.

First on the wave the savage sees afloat,
With uncouth oars, his just invented boat;
With timid eye the tranquil water views,
And close to shore his course secure pursues :
To catch the southern breeze he next essays,
And spreads the sail to cross the spacious bays:
Then, by degrees, forgot dejecting fears,
No more with aspect dread the sea appears;
Intrepid grown, he stretches to the main,
Nor can the shores his eager bark detain;
But far away, the heav'ns alone his guide,
He braves th' Ægean storms and fierce Ionian tide.

LOBB.

sea,

IT is not an ill-founded presumption, that all the early migrations of mankind were made by land. The ocean, which every where surrounds the habitable earth, as well as the various arms of the which separate one region from another, though destined to facilitate the communication between distant countries, seem, at first, to be formed to check the progress of man, and to mark the bounds of that part of the globe to which Nature had confined him. It was long, we may suppose, before men attempted to pass this formidable barrier, and became so skilful

and adventurous as to commit themselves to the mercy of the winds and waves, or to quit their native shore in quest of remote and unknown regions. Horace seems to have this idea, and to consider the first voyager as possessed of an intrepidity more than human:

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Or oak, or brass, with triple fold,
Around that daring mortal's bosom rolled,
Who first, to the wild ocean's rage,
Launched the frail bark-

Jove has the realms of earth in vain
Divided by the inhabitable main,

If ships profane with fearless pride,
Bound o'er th' inviolable tide.

FRANCIS.

Navigation and ship-building are such complicated arts, that they require the ingenuity, as well as experience, of many successive ages, to bring them to any degree of perfection. From the raft or canoe, which first served to carry a savage over the river that obstructed him in the chase, to the construction of a vessel capable of conveying a numerous crew, with safety, to a distant coast, the progress of improvement is immense. Many efforts must have been made, many experiments tried, and much labour and invention employed, before men could accomplish this arduous and important undertaking. The rude and imperfect state in which navigation is still found, among all nations that are not considerably civilized, corresponds with this account of its progress, and demonstrates that, in early times, the art was not so far improved as to enable men to

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