I was much disappointed by this accident; and after having observed at the foot of the mountain the intensity of the magnetic forces, before sunrise, we set out at five in the morning, accompanied by slaves carrying our instruments. Our party consisted of eighteen persons, and we all walked one behind another, in a narrow path, traced on a steep acclivity, covered with turf. We endeavoured first to reach a hill, which towards the south-east seems to form a promontory of the Silla. It is connected with the body of the mountain by a narrow dyke, called by the shepherds the Gate, or Puerta de la Silla. We reached this dyke about seven. The morning was fine and cool, and the sky till then seemed to favour our excursion. I saw that the thermometer kept a little below 14 degrees (11.2 degrees Reaum.). The barometer showed that we were already six hundred and eighty-five toises above the level of the sea, that is, nearly eighty toises higher than at the Venta, where we enjoyed so magnificent a view of the coast. Our guides thought that it would require six hours more to reach the summit of the Silla.
We crossed a narrow dyke of rocks covered with turf; which led us from the promontory of the Puerta to the ridge of the great mountain. Here the eye looks down on two valleys, or rather narrow defiles, filled with thick vegetation. On the right is perceived the ravine which descends between the two peaks to the farm of Munoz; on the left we see the defile of Chacaito, with its waters flowing out near the farm of Gallegos. The roaring of the cascades is heard, while the water is unseen, being concealed by thick groves of erythrina, clusia, and the Indian fig-tree.* (* Ficus nymphaeifolia, Erythrina mitis. Two fine species of mimosa are found in the same valley; Inga fastuosa, and I. cinerea.) Nothing can be more picturesque, in a climate where so many plants have broad, large, shining, and coriaceous leaves, than the aspect of trees when the spectator looks down from a great height above them, and when they are illumined by the almost perpendicular rays of the sun.
From the Puerta de la Silla the steepness of the ascent increases, and we were obliged to incline our bodies considerably forwards as we advanced. The slope is often from 30 to 32 degrees.* (* Since my experiments on slopes, mentioned above in Chapter 1.2, I have discovered in the Figure de la Terre of Bouguer, a passage, which shows that this astronomer, whose opinions are of such weight, considered also 36 degrees as the inclination of a slope quite inaccessible, if the nature of the ground did not admit of forming steps with the foot.) We felt the want of cramp-irons, or sticks shod with iron. Short grass covered the rocks of gneiss, and it was equally impossible to hold by the grass, or to form steps as we might have done in softer ground. This ascent, which was attended with more fatigue than danger, discouraged those who accompanied us from the town, and who were unaccustomed to climb mountains. We lost a great deal of time in waiting for them, and we did not resolve to proceed alone till we saw them descending the mountain instead of climbing up it. The weather was becoming cloudy; the mist already issued in the form of smoke, and in slender and perpendicular streaks, from a small humid wood which bordered the region of alpine savannahs above us. It seemed as if a fire had burst forth at once on several points of the forest. These streaks of vapour gradually accumulated together, and rising above the ground, were carried along by the morning breeze, and glided like a light cloud over the rounded summit of the mountain.
M. Bonpland and I foresaw from these infallible signs, that we should soon be covered by a thick fog; and lest our guides should take advantage of this circumstance and leave us, we obliged those who carried the most necessary instruments to precede us. We continued climbing the slopes which lead towards the ravine of Chacaito. The familiar loquacity of the Creole blacks formed a striking contrast with the taciturn gravity of the Indians, who had constantly accompanied us in the missions of Caripe. The negroes amused themselves by laughing at the persons who had been in such haste to abandon an expedition so long in preparation; above all, they did not spare a young Capuchin monk, a professor of mathematics, who never ceased to boast of the superior physical strength and courage possessed by all classes of European Spaniards over those born in Spanish America. He had provided himself with long slips of white paper, which were to be cut, and flung on the savannah, to indicate to those who might stray behind, the direction they ought to follow. The professor had even promised the friars of his order to fire off some rockets, to announce to the whole town of Caracas that we had succeeded in an enterprise which to him appeared of the utmost importance. He had forgotten that his long and heavy garments would embarrass him in the ascent. Having lost courage long before the creoles, he passed the rest of the day in a neighbouring plantation, gazing at us through a glass directed to the Silla, as we climbed the mountain. Unfortunately for us, he had taken charge of the water and the provision so necessary in an excursion to the mountains. The slaves, who were to rejoin us, were so long detained by him, that they arrived very late, and we were ten hours without either bread or water.
The eastern peak is the most elevated of the two which form the summit of the mountain, and to this we directed our course with our instruments. The hollow between these two peaks has suggested the Spanish name of Silla (saddle), which is given to the whole mountain. The narrow defile which we have already mentioned, descends from this hollow toward the valley of Caracas, commencing near the western dome. The eastern summit is accessible only by going first to the west of the ravine over the promontory of the Puerta, proceeding straight forward to the lower summit; and not turning to the east till the ridge, or the hollow of the Silla between the two peaks, is nearly reached. The general aspect of the mountain points out this path; the rocks being so steep on the east of the ravine that it would be extremely difficult to reach the summit of the Silla by ascending straight to the eastern dome, instead of going by the way of the Puerta.
From the foot of the cascade of Chacaito to one thousand toises of elevation, we found only savannahs. Two small liliaceous plants, with yellow flowers,* alone lift up their heads, among the grasses which cover the rocks. (* Cypura martinicensis, and Sisyrinchium iridifolium. This last is found also near the Venta of La Guayra, at 600 toises of elevation.) A few brambles* (* Rubus jamaicensis.) remind us of the form of our European vegetation. We in vain hoped to find on the mountains of Caracas, and subsequently on the back of the Andes, an eglantine near these brambles. We did not find one indigenous rose-tree in all South America, notwithstanding the analogy existing between the climates of the high mountains of the torrid zone and the climate of our temperate zone. It appears that this charming shrub is wanting in all the southern hemisphere, within and beyond the tropics. It was only on the Mexican mountains that we were fortunate enough to discover, in the nineteenth degree of latitude, American eglantines.* (* M. Redoute, in his superb work on rose-trees, has given our Mexican eglantine, under the name of Rosier de Montezuma, Montezuma rose.)
We were sometimes so enveloped in mist, that we could not, without difficulty, find our way. At this height there is no path, and we were obliged to climb with our hands, when our feet failed us, on the steep and slippery acclivity. A vein filled with porcelain-clay attracted our attention.* (* The breadth of the vein is three feet. This porcelain-clay, when moistened, readily absorbs oxygen from the atmosphere. I found, at Caracas, the residual nitrogen very slightly mingled with carbonic acid, though the experiment was made in phials with ground-glass stoppers, not filled with water.) It is of snowy whiteness, and is no doubt the remains of a decomposed feldspar. I forwarded a considerable portion of it to the intendant of the province. In a country where fuel is not scarce, a mixture of refractory earths may be useful, to improve the earthenware, and even the bricks. Every time that the clouds surrounded us, the thermometer sunk as low as 12 degrees (to 9.6 degrees R.); with a serene sky it rose to 21 degrees. These observations were made in the shade. But it is difficult, on such rapid declivities, covered with a dry, shining, yellow turf, to avoid the effects of radiant heat. We were at nine hundred and forty toises of elevation; and yet at the same height, towards the east, we perceived in a ravine, not merely a few solitary palm-trees, but a whole grove. It was the palma real; probably a species of the genus Oreodoxa. This group of palms, at so considerable an elevation, formed a striking contrast with the willows* scattered on the depth of the more temperate valley of Caracas. (* Salix Humboldtiana of Willdenouw. On the alpine palm-trees, see my Prolegomena de Dist. Plant. page 235.) We here discovered plants of European forms, situated below those of the torrid zone.
After proceeding for the space of four hours across the savannahs, we entered into a little wood composed of shrubs and small trees, called el Pejual; doubtless from the great abundance here of the pejoa (Gaultheria odorata), a plant with very odoriferous leaves.* (* It is a great advantage of the Spanish language, and a peculiarity which it shares in common with the Latin, that, from the name of a tree, may be derived a word designating an association or group of trees of the same species. Thus are formed the words olivar, robledar, and pinal, from olivo, roble, and pino. The Hispano-Americans have added tunal, pejual, guayaval, etc., places where a great many Cactuses, Gualtheria odoratas, and Psidiums, grow together.) The steepness of the mountain became less considerable, and we felt an indescribable pleasure in examining the plants of this region. Nowhere, perhaps, can be found collected together, in so small a space, productions so beautiful, and so remarkable in regard to the geography of plants. At the height of a thousand toises, the lofty savannahs of the hills terminate in a zone of shrubs which, by their appearance, their tortuous branches, their stiff leaves, and the magnitude and beauty of their purple flowers, remind us of what is called, in the Cordilleras of the Andes, the vegetation of the paramos and the punas.* (* For the explanation of these words, see above Chapter 1.5.) We there find the family of the alpine rhododendrons, the thibaudias, the andromedas, the vacciniums, and those befarias with resinous leaves, which we have several times compared to the rhododendron of our European Alps.
Even when nature does not produce the same species in analogous climates, either in the plains of isothermal parallels,* (We may compare together either latitudes which in the same hemisphere present the same mean temperature (as, for instance, Pennsylvania and the central part of France, Chile and the southern part of New Holland); or we may consider the relations that may exist between the vegetation of the two hemispheres under isothermal parallels.) or on table-lands, the temperature of which resembles that of places nearer the poles,* we still remark a striking resemblance of appearance and physiognomy in the vegetation of the most distant countries. (* The geography of plants comprises not merely an examination of the analogies observed in the same hemisphere; as between the vegetation of the Pyrenees and that of the Scandinavian plains; or between that of the Cordilleras of Peru and of the coasts of Chile. It also investigates the relations between the alpine plants of both hemispheres. It compares the vegetation of the Alleghanies and the Cordilleras of Mexico, with that of the mountains of Chile and Brazil. Bearing in mind that every isothermal line has an alpine branch (as, for instance, that which connects Upsala with a point in the Swiss Alps), the great problem of the analogy of vegetable forms may be defined as follows: 1st, examining in each hemisphere, and at the level of the coasts, the vegetation on the same isothermal line, especially near convex or concave summits; 2nd, comparing, with respect to the form of plants, on the same isothermal line north and south of the equator, the alpine branch with that traced in the plains; 3rd, comparing the vegetation on homonymous isothermal lines in the two hemispheres, either in the low regions, or in the alpine regions.) This phenomenon is one of the most curious in the history of organic forms. I say the history; for in vain would reason forbid man to form hypotheses on the origin of things; he still goes on puzzling himself with insoluble problems relating to the distribution of beings.
A gramen of Switzerland grows on the granitic rocks of the straits of Magellan.* (* Phleum alpinum, examined by Mr. Brown. The investigations of this great botanist prove that a certain number of plants are at once common to both hemispheres. Potentilla anserina, Prunella vulgaris, Scirpus mucronatus, and Panicum crus-galli, grow in Germany, in Australia, and in Pennsylvania.) New Holland contains above forty European phanerogamous plants: and the greater number of those plants, which are found equally in the temperate zones of both hemispheres, are entirely wanting in the intermediary or equinoctial region, as well in the plains as on the mountains. A downy-leaved violet, which terminates in some sort the zone of the phanerogamous plants at Teneriffe, and which was long thought peculiar to that island,* is seen three hundred leagues farther north, near the snowy summit of the Pyrenees. (* The Viola cheiranthifolia has been found by MM. Kunth and Von Buch among the alpine plants which Jussieu brought from the Pyrenees.) Gramina and cyperaceous plants of Germany, Arabia, and Senegal, have been recognized among those that were gathered by M. Bonpland and myself on the cold table-lands of Mexico, along the burning shores of the Orinoco, and in the southern hemisphere on the Andes and Quito.* (* Cyperus mucronatus, Poa eragrostis, Festuca myurus, Andropogos avenaceus, Lapago racemosa. (See the Nova Genera et Species Plantarum volume 1 page 25.)) How can we conceive the migration of plants through regions now covered by the ocean? How have the germs of organic life, which resemble each other in their appearance, and even in their internal structure, unfolded themselves at unequal distances from the poles and from the surface of the seas, wherever places so distant present any analogy of temperature? Notwithstanding the influence exercised on the vital functions of plants by the pressure of the air, and the greater or less extinction of light, heat, unequally distributed in different seasons of the year, must doubtless be considered as the most powerful stimulus of vegetation.