The height to which the cones of scoriæ rise from the bottom of the crater at Vesuvius also deserves special attention. Shuckburgh found in 1776 a cone of this nature to be 3932 feet above the level of the Mediterranean; and, according to Lord Minto—a remarkably exact observer—the cone of scoriæ which fell in on the 22nd of October, 1822, was even 4156 feet high. On both occasions therefore the cone of scoriæ in the crater exceeded the highest point of the margin of the crater. On comparing the measurements of Rocca del Palo from 1773 to 1822, one is almost involuntarily led to hazard the bold conjecture that the northern margin of the crater has been gradually upheaved by subterranean forces. The correspondence of the three measurements made between 1773 and 1805 is almost as striking as in those between 1816 and 1822. No doubt can be entertained as to the height being from 3970 to 4021 feet during the latter period. Ought less confidence to be attached to the measurements made thirty or forty years previously, and which only gave from 3875 to 3894 feet? After a longer lapse of time the question may be decided, as to how much is attributable to errors of measurement, and how much to the upheaval of the margin of the crater. There is here no accumulation of loose masses from above; if therefore the solid trachytic lava strata of the Rocca del Palo actually rise, we must assume that they are upheaved from below by volcanic forces.
My learned and indefatigable friend, Oltmanns, has published the details of all these measurements with critical remarks.[[RH]] Would that this work might incite geognosists to enter upon a series of hypsometric observations, by which, in the course of time, Vesuvius, which is, excepting Stromboli, the most accessible of all European volcanos, may be thoroughly understood in all periods of its development.
[109]. p. 371—“At elevations where the pressure is less.”
Compare Leopold von Buch on the Peak of Teneriffe, in his Physikalische Beschreibung der canarischen Inseln, 1825, s. 213, and in the Abhandlungen der königl. Akademie zu Berlin, aus den J. 1820–21, s. 99.
[110]. p. 373—“Springs which rise from different depths.”
Compare Arago in the Annuaire du Bureau des Longitudes pour 1835, p. 234. The increase of the temperature is in our latitudes 1° Fahr. for nearly every 54 feet. In the Artesian boring at the New Salt-works (Oeynhausen’s Bath) near Minden, which is the greatest known depth that has been reached below the surface of the sea, the temperature of the water at 2231 feet, is fully 91° Fahrenheit, whilst the mean upper temperature of the air may be assumed at 49°·3 Fahr. It is very remarkable that, even in the third century, Saint Patricius, bishop of Pertusa, should have been led, from the thermal springs near Carthage, to form a very correct view of such an increase of heat.[[RI]]
VITAL FORCE, OR THE RHODIAN GENIUS.
The Syracusans, like the Athenians, had their Poecile,[[RJ]] where representations of gods and heroes, the works of Grecian and Italian art, adorned the richly decorated halls of the Portico. Incessantly the people streamed thither; the young warrior to feast his eyes upon the deeds of his forefathers, the artist to contemplate the works of the great masters. Among the numerous paintings which the active enterprise of the Syracusans had collected from the mother country, there was but one which for full a century had continued to attract the attention of every visitor. Even when, the Olympian Jupiter, Cecrops, the founder of cities, and the heroic courage of Harmodius and Aristogiton, failed to attract admirers, a dense crowd still pressed round this one picture. Whence this preference? Was the painting a rescued work of Apelles, or did it bear the impress of the school of Callimachus? No! although it possessed both grace and beauty, yet neither in the blending of the colours, nor in the character and style of its composition, could it be compared with many other paintings in the Poecile.
The crowd—and how numerous are the classes included in this denomination—ever admires and wonders at what it does not understand! For more than a century had that painting been publicly exhibited, and yet, although Syracuse contained within its narrow limits more artistic genius than all the rest of sea-girt Sicily, the riddle of its meaning still remained unsolved. It was not even known to what temple it had formerly belonged, for it had been saved from a stranded vessel, which was only conjectured, from the freight it carried, to have come from Rhodes.
The foreground of the picture was occupied by a numerous group of youths and maidens, whose uncovered limbs, although well formed, were not cast in that slender mould which we so much admire in the statues of Praxiteles and Alcamenes. The fuller development of their limbs, which bore indications of laborious exercise,—the human expression of passion and of care stamped on their features,—all seemed to divest them of a heavenly or God-like type, and to fix them as creatures of the earth. Their hair was simply adorned with leaves and wild flowers. Their arms were extended towards each other with impassioned longing, but their earnest and mournful gaze was rivetted on a Genius, who, surrounded by a brilliant halo, hovered in the midst of the group. On his shoulder was a butterfly, and in his right hand he held aloft a flaming torch. His limbs were moulded with child-like grace; his eye radiant with celestial light. He looked imperiously upon the youths and maidens at his feet. No other characteristic traits could be distinguished in the picture. Some, however, thought they could perceive at his foot the letters ζ and σ, and as antiquarians were then no less bold than they are now, they inferred, though far from happily, that the artist was called Zenodorus, the name borne at a later date by the modeller of the Colossus of Rhodes.