ANNOTATIONS AND ADDITIONS.

[38] p. 226.—“A more complete determination of the height of all parts of the margin of the crater.”

Oltmanns, my astronomical fellow labourer, of whom, alas! science has been early deprived, re-calculated the barometric measurements of Vesuvius referred to in the preceding memoir (of the 22d and 25th of November and of the 1st of December, 1822), and has compared the results with the measurements which have been communicated to me in manuscript by Lord Minto, Visconti, Monticelli, Brioschi, and Poulett Scrope.

A. Rocca del Palo, the highest and northern margin of the Crater of Vesuvius.

Toises.Eng. ft.
Saussure, barometric measurement computed in 1773, probably by Deluc’s formula6093894
Poli, 1794, barometric6063875
Breislak, 1794, barometric (but, like Poli, the formula employed uncertain)6133920
Gay-Lussac, Leopold von Buch, and Humboldt, 1805, barometric, computed by Laplace’s formula, as are also all the barometric results which follow6033856
Brioschi, 1810, trigonometric6384080
Visconti, 1816, trigonometric6223977
Lord Minto, 1822, barometric, often repeated6213971
Poulett Scrope, 1822, barometric, somewhat uncertain from the proportion between the diameters of the tube and cistern being unknown6043862
Monticelli and Covelli, 18226243990
Humboldt, 18226294022

Most probable result 317 toises, or 2027 English feet, above the Hermitage; or 625 toises, or 3996 English feet, above the level of the sea.

B. The lowest and southern margin of the crater opposite to Bosche Tre Case.

Toises.Eng. ft.
After the eruption of 1794 this edge became 400 (426 Eng.) feet lower than the Rocca del Palo; therefore if we estimate the latter at 625 toises (3996 English feet)5593574
Gay-Lussac, Leopold von Buch, and Humboldt, 1805, barometric5343414
Humboldt, 1822, barometric5463491

C. Height of the cone of scoriæ inside the crater, which fell in on the 22d of October, 1822.

Toises.Eng. ft.
Lord Minto, barometric6504156
Brioschi, trigonometric, according to different combinations either6364066
Or6414098

Probable final result for the height of the above-mentioned cone of scoriæ 646 toises, or 4130 English feet.

D. Punta Nasone, highest summit of the Somma.

Toises.Eng. ft.
Schuckburgh, 1794, barometric, probably computed by his own formula5843734
Humboldt, 1822, barometric, Laplace’s formula5863747

E. Plain of the Atrio del Cavallo.

Toises.Eng. ft.
Humboldt, 1822, barometric4032577

F. Foot of the cone of ashes.

Toises.Eng. ft.
Gay-Lussac, Leopold von Buch, and Humboldt, 1805, barometric3702366
Humboldt, 1822, barometric3882481

G. Hermitage del Salvatore.

Toises.Eng. ft.
Gay-Lussac, Leopold von Buch, and Humboldt, 1805, barometric3001918
Lord Minto, 1822, barometric307.91969
Humboldt, 1822, barometric repeated308.71974

Part of my measurements have been printed in Monticelli’s Storia de’ fenomeni del Vesuvio, avvenuti negli anni 1821-1823, p. 115; but the neglected correction for the height of the mercury in the cistern has somewhat disfigured the results as there published. When it is remembered that the results given in the above table were obtained with barometers of very different constructions, at various hours of the day, with winds from very different quarters, and on the unequally heated declivity of a volcano, in a locality in which the decrease of atmospheric temperature differs greatly from that which is supposed in our barometric formulæ,—the agreement will be found to be as great as could be expected, and quite satisfactory.

My measurements in 1822, at the time of the Congress of Verona, when I accompanied the late King of Prussia to Naples, were made with more care and under more favourable circumstances than those of 1805. Differences of height are besides always to be preferred to absolute heights, and these show that since 1794 the difference between the heights of the edges of the crater at the Rocca del Palo and on the side towards Bosco Tre Case has continued almost the same. I found it in 1805 exactly 69 toises (441 English feet), and in 1822 almost 82 toises (524 English feet). A distinguished geologist, Mr Poulett Scrope, found 74 toises (473 English feet), although the absolute heights which he assigns to the two sides of the crater appear to be rather too small. So little variation in a period of twenty-eight years, in which there were such violent commotions in the interior of the crater, is certainly a striking phænomenon.

The height attained by cones of scoriæ rising from the floor of the crater of Vesuvius is also deserving of particular attention. In 1776 Schuckburgh found such a cone 615 toises, or 3932 English feet, above the surface of the Mediterranean: according to the measurements of Lord Minto, (a very accurate observer,) the cone of scoriæ which fell in on the 22d of October, 1822, even attained the height of 650 toises, or 4156 English feet. On both occasions, therefore, the height of the cones of scoriæ in the crater surpassed that of the highest part of the margin of the crater. When we compare together the measurements of the Rocca del Palo from 1773 to 1822, we are almost involuntarily led to entertain the bold conjecture that the north margin of the crater has been gradually upraised by subterranean forces. The accordance of the three measurements between 1773 and 1805 is almost as striking as that of those taken from 1816 to 1822. In the latter period we cannot doubt the height being from about 621 to 629 toises (3970 to 4022 English feet). Are the measurements made from thirty to forty years earlier, which gave only 606 to 609 toises (3875 to 3894 English feet), less certain? At some future day, after longer periods shall have elapsed, it will be possible to decide what is due to errors of measurement, and what to an actual rise in the margin of the crater. There cannot be in this case any accumulation of loose materials from above. If the solid trachyte-like lava beds of the Rocca del Palo really become higher, we must assume them to be upheaved from below by volcanic forces.

My learned and indefatigable friend Oltmanns has placed all the details of the above measurements before the public, accompanied by a careful critical examination of them, in the Abhandl. der königl. Akademie der Wissenschaften zu Berlin, 1822-1823, S. 3-20. May this investigation be the means of inducing geologists frequently to examine hypsometrically this low and most easily accessible (except Stromboli) of the European volcanos, so that in the course of centuries there may be obtained a frequently checked and accurate account of its periods of development!

[39] p. 235.—“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, 1820-1821, S. 99.

[40] p. 289—“Waters of springs rising from different depths.”

Compare Arago in the Annuaire du Bureau des Longitudes pour 1835, p. 234. The increase of temperature is in our latitudes 1° of Reaumur (2°.25 of a degree of Fahrenheit) for every 113 Parisian feet (120.5 English feet), or 1° Fah. to 53.5 English feet nearly. In the Artesian boring at New Salzwerk (Oeynhausen’s Bad), not far from Minden, which is the greatest known depth below the level of the sea, the temperature of the water at 2094½ Parisian feet (2232¼ Eng.) is fully 26°.2 Reaumur, or 91° Fahr.; while the mean temperature of the air above may be taken at 7°.7 Reaumur, or 49°.2 Fahr. It is very remarkable that in the third century Saint Patricius, Bishop of Pertusa, was led by seeing the hot springs near Carthage to a very just view respecting the cause of such an increase of heat. (Acta S. Patricii, p. 555, ed. Ruinart; Kosmos, Bd. i. S. 231,—English Edition, Vol. i. p. 211.)

THE
VITAL FORCE;
OR,
THE RHODIAN GENIUS.

[FIRST PRINTED IN 1795.]

The Syracusans, like the Athenians, had their Pœcile, in which representations of gods and heroes, the works of Grecian and Italian art, adorned the halls, glowing with varied colours. The people resorted thither continually; the young warriors to contemplate the exploits of their ancestors, the artists to study the works of the great masters. Among the numerous paintings which the active zeal of the Syracusans had collected from the mother country, there was one which, for a century past, had particularly attracted the attention of spectators. Sometimes the Olympian Jove, Cecrops the founder of cities, and the heroic courage of Harmodius and Aristogiton, would want admirers, while men pressed in crowded ranks around the picture of which we speak. Whence this preference? Was it a rescued work of Apelles, or of the school of Callimachus? No; it possessed indeed grace and beauty; but yet neither in the blending of the colours, nor in the character and style of the entire picture, could it be compared with many other paintings in the Pœcile.

The multitude (comprehending therein many classes of society), often regard with astonishment and admiration what they do not comprehend: this picture had occupied its place for a hundred years; but though Syracuse contained within the narrow limits enclosed by its walls more of the genius of art than the whole of the remainder of sea-surrounded Sicily, no one had yet divined the hidden meaning of the design. It was even uncertain to what temple the painting had originally belonged, for it had been rescued from a shipwrecked vessel, which was only conjectured from the merchandise it contained to have come from Rhodes.

On the foreground of the picture youths and maidens formed a closely crowded group. They were without clothing and well formed, but at the same time did not exhibit the more noble and graceful proportions admired in the statues of Praxiteles and Alcamenes. Their robust limbs, shewing the traces of laborious efforts, and the purely terrestrial expression of their desires and sorrows, seemed to take from them every thing of a diviner character, and to chain them exclusively to their earthly habitation. Their hair was simply ornamented with leaves and field-flowers. Their arms were outstretched towards each other, as if to indicate their desire of union, but their troubled looks were turned towards a Genius who, surrounded by bright light, hovered in the midst. A butterfly was placed on his shoulder, and in his hand he held on high a lighted torch. The contours of his form were soft and child-like, but his glance was animated by celestial fire: he looked down as a master upon the youths and maidens at his feet. Nothing else that was characteristic could be discovered in the picture. Some persons thought they could make out at its foot the letters ζ and ς, from whence (as antiquaries were then no less bold in their conjectures than they now are), they took occasion to infer, in a somewhat forced manner, the name of Zenodorus; thus attributing the work to a painter of the same name as the artist who at a later period cast the Colossus of Rhodes.

The “Rhodian Genius,” however,—for such was the name given to the picture,—did not want for commentators and interpreters in Syracuse. Amateurs of the arts, and especially the younger amongst them, on returning from a short visit to Corinth or Athens, would have thought it equivalent to renouncing all pretensions to connoisseurship if they had not been provided with some new explanation. Some regarded the Genius as the personification of Spiritual Love, forbidding the enjoyment of sensual pleasures; others said it was the assertion of the empire of Reason over Desire: the wiser among the critics were silent, and presuming some high though yet undiscovered meaning, examined meanwhile with pleasure the simple composition of the picture.

Still, however, the question remained unsolved. The picture had been copied with various additions and sent to Greece, but not the least light had been thrown on its origin; when at length, at the season of the early rising of the Pleiades, and soon after the reopening of the navigation of the Egean Sea, ships from Rhodes entered the port of Syracuse, bearing a precious collection of statues, altars, candelabras, and paintings, which Dionysius’s love of art had caused to be brought together from different parts of Greece. Among the paintings was one which was immediately recognised as the companion or pendent of the Rhodian Genius: the dimensions were the same, and the colouring similar, but in a better state of preservation: the Genius was still the central figure, but the butterfly was no longer on his shoulder; his head was drooping, and his torch extinguished and inverted. The youths and maidens pressing around him had met and embraced; their glance, no longer subdued or sad, announced, on the contrary, emancipation from restraint, and the fulfilment of long-cherished desires.

The Syracusan antiquaries were already seeking to modify the explanations they had previously proposed, so as to adapt them to the newly-arrived picture, when Dionysius commanded the latter to be carried to the house of Epicharmus, a philosopher of the Pythagorean school, who dwelt in a remote part of Syracuse called Tyche. Epicharmus rarely presented himself at the court of Dionysius, for although the latter was fond of calling around him the most distinguished men from all the Greek colonial cities, yet the philosopher found that the proximity of princes takes even from men of the greatest intellectual power part of their spirit and their freedom. He devoted himself unceasingly to the study of natural things, their forces or powers, the origin of animals and plants, and the harmonious laws in accordance with which the heavenly bodies, as well as the grains of hail and the flakes of snow, assume their distinctive forms. Oppressed with age, and unable to proceed far without assistance, he caused himself to be conducted daily to the Pœcile, and thence to the entrance of the port, where, as he said, his eyes received the image of the boundless and the infinite which his spirit ever strove in vain to apprehend. He lived honoured alike by the tyrant, whose presence he avoided, and by the lower classes of the people, whom he met gladly, and often with friendly help.

Exhausted with fatigue, he was reposing on his couch, when the newly-arrived picture was brought to him by the command of Dionysius. Care had been taken to bring, at the same time, a faithful copy of the “Rhodian Genius,” and the philosopher desired the two paintings to be placed side by side before him. After having remained for some time with his eyes fixed upon them, and absorbed in thought, he called his scholars together, and spoke to them in the following terms, in a voice which was not without emotion:—

“Withdraw the curtain from the window, that I may enjoy once more the view of the fair earth animated with living beings. During sixty years I have reflected on the internal motive powers of nature, and on the differences of substances: to-day for the first time the picture of the Rhodian Genius leads me to see more clearly that which I had before only obscurely divined. As living beings are impelled by natural desires to salutary and fruitful union, so the raw materials of inorganic nature are moved by similar impulses. Even in the reign of primeval night, in the darkness of chaos, elementary principles or substances sought or shunned each other in obedience to indwelling dispositions of amity or enmity. Thus the fire of heaven follows metal, iron obeys the attraction of the loadstone, amber rubbed takes up light substances, earth mixes with earth, salt collects together from the water of the sea, and the acid moisture of the Stypteria (στυπτηρια υγρα), as well as the flocculent salt Trichitis, love the clay of Melos. In inanimate nature all things hasten to unite with each other according to their particular laws. Hence no terrestrial element (and who would dare to include light among the number of such elements?) is to be found anywhere in its pure and primitive simple state. Each as soon as formed tends to enter into new combinations, and the art of man is needed to disjoin and present in a separated state substances which you would seek in vain in the interior of the earth, and in the fluid oceans of air or water. In dead inorganic matter, entire inactivity and repose reign so long as the bonds of affinity continue undissolved, so long as no third substance comes to join itself to the others. But even then, the action and disturbance produced are soon again succeeded by unfruitful repose.

“It is otherwise, however, when the same substances are brought together in the bodies of plants and animals. In these the vital force or power reigns supreme, and regardless of the mutual amity or enmity of the atoms recognised by Democritus, commands the union of substances which in inanimate nature shun each other, and separates those which are ever seeking to enter into combination.

“Now come nearer to me, my friends; look with me on the first of the pictures before us, and recognise in the Rhodian Genius, in the expression of youthful energy, in the butterfly on his shoulder, and in the commanding glance of his eye, the symbol of vital force animating each individual germ of the organic creation. At his feet are the earthy elements desiring to mix and unite, conformably to their particular tendencies. The Genius, holding aloft his lighted torch with commanding gesture, controls and constrains them, without regard to their ancient rights, to obey his laws.

“Now view with me the new picture which the tyrant has sent to me for explanation: turn your eyes from the image of life to that of death. The butterfly has left its former place and soars upwards; the extinguished torch is reversed, the head of the youth has sunk: the spirit has fled to other spheres, and the vital force is dead. Now the youths and maidens joyfully join hands, the earthy substances resume their ancient rights: they are freed from the chains that bound them, and follow impetuously after long restraint the impulse to union.—Thus inert matter, animated awhile by vital force, passes through an innumerable diversity of forms, and perhaps in the same substance which once enshrined the spirit of Pythagoras, a poor worm may have enjoyed a momentary existence.

“Go, Polycles, and tell Dionysius what thou hast heard;—and you my friends, Euryphamos, Lysis, and Scopas, come nearer to me and support me; I feel that in my weakened frame the enfeebled vital power will not long hold in subjection the earthly substances which reclaim their ancient liberty. Lead me once again to the Pœcile, and thence to the sea shore; soon you will collect my ashes.”