I would fain be permitted to add one yet bolder observation to those I have already ventured to advance. May not the cause of one of the most wonderful phenomena presented by the study of petrifactions, be dependent on the condition of the inner heat of our planet, which is indicated by thermometric experiments on springs[[110]] rising from different depths, and by observations on volcanos? We find tropical animals, arborescent ferns, palms, and bamboos, buried in the cold north, and everywhere the primitive world presents a distribution of organic structures wholly at variance with existing climatic relations. Many hypotheses have been advanced in elucidation of so important a problem, such as the approximation of a comet, the altered obliquity of the ecliptic, and the increased intensity of the sun’s light; but none of these have satisfied at once the astronomer, the physicist, and the geologist. I, for my part, would willingly leave undisturbed the axis of the earth or the light of the sun’s disk, (from whose spots a celebrated astronomer explained fruitfulness and failure of crops,) yet it appears to me that in every planet there exist, independently of its relations to a central body and its astronomical position, numerous causes for the development of heat, in processes of oxidation, in precipitation, in the chemically altered capacity of bodies, the increase of electro-magnetic tension, and in the channels of communication opened between its internal and external parts.
Wherever, in the primitive world, heat was radiated from the deeply fissured crust of the earth, palms, arborescent ferns, and all the animals of the torrid zone, could perhaps have flourished for centuries over extensive tracts of land. According to this view, which I have already published in my work entitled Geognostischer Versuch über die Lagerung der Gebirgsarten in beiden Hemisphären,[[RG]] the temperature of volcanos would be that of the interior of our earth itself, and the same causes which now occasion such fearfully devastating results, may have been able to produce, in every zone, the most luxuriant vegetation on the newly oxidized crust of the earth and on the deeply fissured strata of rocks.
Should it be assumed, for the purpose of explaining the wonderful distribution of tropical forms in their ancient mausolea, that the long-haired elephantine animals, which are now found embedded in ice, were once indigenous to northern latitudes, and that animals of similar forms, belonging to the same type, as, for instance, lions and lynxes, were capable of living in wholly different climates, such a mode of explanation would at all events not admit of being extended to vegetable products. From causes developed by the physiology of vegetation, palms, bananas, and arborescent monocotyledons, are unable to endure the deprivation of their appendicular organs, by the northern cold; and in the geological problem which we are here considering, it seems to me a matter of difficulty to admit any distinction between vegetable and animal structures. One and the same mode of explanation must be applied to both forms.
In concluding this treatise, I have added some uncertain and hypothetical conjectures to the facts which have been collected in widely remote regions of the earth. The philosophical study of nature rises above the requirements of mere delineation, and does not consist in the sterile accumulation of isolated facts. The active and inquiring spirit of man may therefore be occasionally permitted to escape from the present into the domain of the past, to conjecture that which cannot yet be clearly determined, and thus to revel amid the ancient and ever-recurring myths of geology.
EXPLANATORY ADDITIONS.
[108]. P. 363.—“A more complete determination of the margins of the Crater of Mount Vesuvius.”
My astronomical fellow-labourer, Oltmanns, who was unhappily too early lost to science, has re-calculated the barometric measurements I made on Mount Vesuvius (from the 22nd to the 25th of November, and on the 1st of December, 1822), and compared the results with those yielded by the measurements given to me in manuscript by Lord Minto, Visconti, Monticelli, Brioschi, and Poulett Scrope.
| A. Rocca del Palo, the highest northern margin of the Crater of Vesuvius, was estimated by— | |
|---|---|
| Feet. | |
| Saussure, in 1773, barometrically, probably according to Deluc’s formula | 3894 |
| Poli (1794), barometrically | 3875 |
| Breislak (1794), barometrically, although, as in the case of Poli, it is uncertain what formula was used | 3920 |
| Gay-Lussac, Leopold von Buch, and Humboldt (1805), barometrically, according to the formula of Laplace, as in all the following barometric results | 3856 |
| Brioschi (1810), trigonometrically | 4079 |
| Visconti (1816), trigonometrically | 3977 |
| Lord Minto (1822), barometrically, and frequently repeated | 3971 |
| Poulett Scrope (1822). This calculation is somewhat uncertain, owing to the unknown relation of the diameters of the tubes to those of the cistern | 3862 |
| Monticelli and Covelli (1822) | 3990 |
| Humboldt (1822) | 4022 |
| The most probable final result is 2026 feet above the hermitage, or 3996 feet above the level of the sea. | |
| B. The lowest south-eastern margin of the Crater, opposite Bosche Tre Case. | |
| After the eruption of 1794, this margin was 426 feet lower than the Rocca del Palo, consequently, if the latter be estimated at 3996 feet, it would be | 3570 |
| Gay-Lussac, Leopold von Buch, and Humboldt (1805), barometrically | 3414 |
| Humboldt (1822), barometrically | 3491 |
| C. The elevation of the cone of scoriæ that fell into the Crater on the 22nd October, 1822. | |
| Lord Minto, barometrically | 4156 |
| Brioschi, trigonometrically, according to different combinations— | |
| Either | 4067 |
| Or | 4099 |
| The most probable final result for the height of the cone of scoriæ that fell in during the year 1822, is 4131 feet. | |
| D. Punta Nasone, the highest summit of the Somma. | |
| Shuckburgh (1794), barometrically, probably according to his own formula | 3734 |
| Humboldt (1822), barometrically, according to the formula of Laplace | 3747 |
| E. Plain of the Atrio del Cavallo. | |
| Humboldt (1822), barometrically | 2577 |
| F. Base of the cone of ashes. | |
| Gay-Lussac, Leopold von Buch, and Humboldt (1805), barometrically | 2366 |
| Humboldt (1822), barometrically | 2482 |
| G. Hermitage of Salvatore. | |
| Gay-Lussac, Leopold von Buch, and Humboldt (1805), barometrically | 1918 |
| Lord Minto (1822), barometrically | 1969 |
| Humboldt (1822), again barometrically | 1974 |
Some of my measurements have appeared in Monticelli’s Storia de’ fenomeni del Vesuvio, avvenuti negli anni 1821–1823, p. 115, but owing to the correction of the height of the mercury in the cistern having been omitted, the numbers are not given with perfect exactness. When it is remembered that the results contained in the above table were obtained with barometers of very different construction, at different hours of the day, during the prevalence of various winds, and on the unequally heated declivity of a volcano, in a locality where the decrease of the atmospheric temperature differs very considerably from that assumed in our barometrical formulæ, the amount of correspondence between the various results will appear sufficiently satisfactory.
My measurements of 1822, at the time of the Congress of Verona, when I accompanied the late King to Naples, were conducted with more care and under more favourable circumstances than those of 1805. Differences of elevations are moreover always preferable to absolute elevations. These differences show, that since 1794, the relative condition of the margins of the Rocca del Palo and of that towards Bosche Tre Case had remained almost the same. I found, in 1805, for the height, 441, and in 1822, nearly 524 feet. A distinguished geologist, Mr. Poulett Scrope, obtained 473 feet, although his absolute heights for these two margins of the crater appear somewhat too low. So inconsiderable a variation in a period of twenty-eight years, and during violent disturbances in the interior of the mountain, is undoubtedly a remarkable phenomenon.