A more richly varied and broken outline gives to the northern shore of the Mediterranean an advantage over the southern or Lybian shore, which according to Strabo was remarked by Eratosthenes. The three great peninsulas, the Iberian, the Italian, and the Hellenic, with their sinuous and deeply indented shores, form, in combination with the neighbouring islands and opposite coasts, many straits and isthmuses. The configuration of the continent and the islands, the latter either severed from the main or volcanically elevated in lines, as if over long fissures, early led to geognostical views respecting eruptions, terrestrial revolutions, and overpourings of the swollen higher seas into those which were lower. The Euxine, the Dardanelles, the Straits of Gades, and the Mediterranean with its many islands, were well fitted to give rise to the view of such a system of sluices. The Orphic Argonaut, who probably wrote in Christian times, wove antique legends into his song; he describes the breaking up of the ancient Lyktonia into several islands, when ‘the dark-haired Poseidon, being wroth with Father Kronion, smote Lyktonia with the golden trident.’ Similar phantasies, which indeed may often have arisen from imperfect knowledge of geographical circumstances, proceeded from the Alexandrian school, where erudition abounded, and a strong predilection was felt for antique legends. It is not necessary to determine here whether the myth of the Atlantis broken into fragments should be regarded as a distant and western reflex of that of Lyktonia (as I think I have elsewhere shewn to be probable), or whether, as Otfried Müller considers, “the destruction of Lyktonia (Leuconia) refers to the Samothracian tradition of a great flood which had changed the form of that district.”
[9] p. 12.—“Prevents precipitation taking place from clouds.”
The vertically-ascending current of the atmosphere is a principal cause of many most important meteorological phenomena. When a desert or a sandy plain partly or entirely destitute of plants is bounded by a chain of high mountains, we see the sea breeze drive the dense clouds over the desert without any precipitation taking place before they have reached the mountain-ridge. This phenomenon was formerly explained in a very inappropriate manner by a supposed superior attraction exercised by the mountains on the clouds. The true reason of the phenomenon appears to consist in the ascending column of warm air which rises from the sandy plain, and prevents the vesicles of vapour from being dissolved. The more complete the absence of vegetation, and the more the sand is heated, the greater is the height of the clouds, and the less can any fall of rain take place. When the clouds reach the mountains these causes cease to operate; the play of the vertically-ascending atmospheric current is feebler, the clouds sink lower, and dissolve in rain in a cooler stratum of air. Thus, in deserts, the want of rain, and the absence of vegetation, act and react upon each other. It does not rain, because the naked sandy surface having no vegetable covering, becomes more powerfully heated by the solar rays, and thus radiates more heat; and the absence of rain forbids the desert being converted into a steppe or grassy plain, because without water no organic development is possible.
[10] p. 14.—“The mass of the earth in solidifying and parting with its heat.”
If, according to the hypothesis of the Neptunists, now long since obsolete, the so-called primitive rocks were precipitated from a fluid, the transition of the crust of the earth from a fluid to a solid state must have been accompanied by an enormous disengagement of heat, which would in turn have caused fresh evaporation and fresh precipitations. The later these precipitations, the more rapid, tumultuous, and uncrystalline they would have been. Such a sudden disengagement of heat might cause local augmentations of temperature independent of the height of the pole or the latitude of the place, and independent of the position of the earth’s axis; and the temperatures thus caused would influence the distribution of plants. The same sudden disengagement of heat might also occasion a species of porosity, of which there seem to be indications in many enigmatical geological phenomena in sedimentary rocks. I have developed these conjectures in detail in a small memoir “über ursprungliche Porosität.” (See my work entitled Versuche über die chemische Zersetzung des Luftkreises, 1799, S. 177; and Moll’s Jahrbücher der Berg- und Hüttenkunde, 1797, S. 234.) According to the newer views which I now entertain, the shattered and fissured earth, with her molten interior, may long have maintained a high temperature on her oxydised surface, independently of position in respect to the sun and of latitude. Would not the climate of Germany be wonderfully altered, and that perhaps for centuries, if there were opened a fissure a thousand fathoms in depth, reaching from the shores of the Adriatic to the Baltic? If in the present condition of our planet, the stable equilibrium of temperature, first calculated by Fourier in his Théorie analytique de la chaleur, has been almost completely restored by radiation from the earth into space; and if the external atmosphere now only communicates with the molten interior through the inconsiderable openings of a few volcanoes,—in the earlier state of things numerous clefts and fissures, produced by the frequently recurring corrugations of the rocky strata of the globe, emitted streams of heated air which mingled with the atmosphere and were entirely independent of latitude. Every planet must thus in its earliest condition have for a time determined its own temperature, which afterwards becomes dependent on the position relatively to the central body, the Sun. The surface of the Moon also shows traces of this reaction of the interior upon the crust.
[11] p. 14.—“The mountain declivities of the southern part of Mexico.”
The greenstone in globular concretions of the mountain district of Guanaxuato is quite similar to that of the Franconian Fichtel-Gebirge. Both form grotesquely shaped summits, which pierce through and cover the transition argillaceous schists. In the same manner, pearl stone, porphyritic schists, trachyte, and pitch-stone porphyry, constitute rocks similar in form in the Mexican mountains near Cinapecuaro and Moran, in Hungary, in Bohemia, and in Northern Asia.
[12] p. 16.—“The dragon-tree of Orotava.”
This colossal dragon-tree, Dracæna draco, stands in the garden of Dr. Franqui in the small town of Oratava, the ancient Taoro, one of the most delightful spots in the world. In June 1799, when we ascended the Peak of Teneriffe, we measured the circumference of the tree, and found it nearly 48 English feet. Our measurement was taken several feet above the root. Lower down, and nearer to the ground, Le Dru made it nearly 79 English feet. Sir George Staunton found the diameter still as much as 12 feet at the height of 10 feet above the ground. The height of the tree is not much above 69 English feet. According to tradition, this tree was venerated by the Guanches (as was the ash-tree of Ephesus by the Greeks, or as the Lydian plane-tree which Xerxes decked with ornaments, and the sacred Banyan-tree of Ceylon), and at the time of the first expedition of the Béthencourts in 1402, it was already as thick and as hollow as it now is. Remembering that the Dracæna grows extremely slowly, we are led to infer the high antiquity of the tree of Orotava. Bertholet, in his description of Teneriffe, says, “En comparant les jeunes Dragonniers, voisins de l’arbre gigantesque, les calculs qu’on fait sur l’age de ce dernier effraient l’imagination.” (Nova Acta Acad. Leop. Carol. Naturæ Curiosorum, T. xiii. 1827, p. 781.) The dragon-tree has been cultivated in the Canaries, and in Madeira and Porto Santo, from the earliest times; and an accurate observer, Leopold von Buch, has even found it wild in Teneriffe, near Igueste. Its original country, therefore, is not India, as had long been believed; nor does its appearance in the Canaries contradict the opinion of those who regard the Guanches as having been an isolated Atlantic nation without intercourse with African or Asiatic nations. The form of the Dracænas is repeated at the southern extremity of Africa, in the Isle of Bourbon, and in New Zealand. In all these distant regions species of the genus in question are found, but none have been met with in the New Continent, where its form is replaced by that of the Yucca. Dracæna borealis of Aiton is a true Convallaria, and has all the “habitus” of that genus. (Humboldt, Rel. hist. T. i. p. 118 and 639.) I have given a representation of the dragon-tree of Orotava, taken from a drawing made by F. d’Ozonne in 1776, in the last plate of the Picturesque Atlas of my American journey. (Vues des Cordillères et Monumens des Peuples indigènes de l’Amérique, Pl. lxix.) I found d’Ozonne’s drawing among the manuscripts left by the celebrated Borda, in the still unprinted travelling journal entrusted to me by the Dépôt de la Marine, and from which I borrowed important astronomically-determined geographical, as well as barometric and trigonometric notices. (Rel. hist. T. i. p. 282.) The measurement of the dragon-tree of the Villa Franqui was made on Borda’s first voyage with Pingré, in 1771; not in his second voyage, in 1776, with Varela. It is affirmed that in the early times of the Norman and Spanish Conquests, in the 15th century, Mass was said at a small altar erected in the hollow trunk of the tree. Unfortunately the dragon-tree of Orotava lost one side of its top in the storm of the 21st of July, 1819. There is a fine and large English copperplate engraving which represents the present state of the tree with remarkable truth to nature.
The monumental character of these colossal living vegetable forms, and the kind of reverence which has been felt for them among all nations, have occasioned in modern times the bestowal of greater care in the numerical determination of their age and the size of their trunks. The results of these inquiries have led the author of the important treatise, “De la longévité des Arbres,” the elder Decandolle, Endlicher, Unger, and other able botanists, to consider it not improbable that the age of several individual trees which are still alive goes back to the earliest historical periods, if not of Egypt, at least of Greece and Italy. It is said in the Bibliothèque Universelle de Genève, 1831, T. lxvii. p. 50:—“Plusieurs exemples semblent confirmer l’idée qu’il existe encore sur le globe des arbres d’une antiquité prodigieuse, et peut-être témoins de ses dernières révolutions physiques. Lorsqu’on regarde un arbre comme un agrégat d’autant d’individus soudés ensemble qu’il s’est développé de bourgeons à sa surface, on ne peut pas s’étonner si, de nouveaux bourgeons s’ajoutant sans cesse aux anciens, l’agrégat qui en résulte n’a point de terme nécessaire à son existence.” In the same manner Agardh says:—“If in trees there are produced in each solar year new parts, so that the older hardened parts are replaced by new ones capable of conducting sap, we see herein a type of growth limited only by external causes.” He ascribes the shortness of the life of herbs, or of such plants as are not trees, “to the preponderance of the production of flowers and fruit over the formation of leaves.” Unfruitfulness is to a plant a prolongation of life. Endlicher cites the example of a plant of Medicago sativa, var. β versicolor, which, bearing no fruit, lived eighty years. (Grundzüge der Botanik, 1843, S. 1003).