waters, absorbed by the power of vegetation, are not fed by springs in proportion to their loss, this marshy soil will by degrees be dried up, and will be covered in time with fertile meadows and trees of all sorts, and will then be fit for cultivation.

What I have here said with respect to the gradual progress of vegetation is in no degree conjectural: we find its proof at almost every step, as well in the bosom of the earth as at its surface, especially in soil which has not been overturned by recent revolutions. In how many places do we not meet, beneath the bed of vegetable or argillaceous earth, ancient peat-bogs cxtended over strata of sand or heaps of rolled stones; an evident proof that this soil has formerly been traversed by the waters of rivers, or occupied by those of lakes. The vast marshes of the Somme furnish us with one example among a thousand. The soil is often covered, as M. Girard has observed, with a layer of earth adapted for vegetation, about two feet in its greatest thickness; the height of the bed of peat on which it rests is from six to ten feet thick between Amiens and Pecquigny; it increases to thirty feet opposite the villages of L'Etoile and Long, beyond which it gradually diminishes. The low part of the city of Amiens, according to the observations of M. Sellier, is built upon a bed of peat, which is sometimes more than twelve feet thick; it rests upon a bed of marl, which is itself supported by bed of sand and pebbles, mixed with marine shells. This vast formation has therefore been long occupied by great lakes, as is proved by the discovery which has been made of several boats and Roman arms preserved in the peat at different depths.

a

We are not permitted to follow the establishment of vege tation in the depths of the ocean; but if marine plants, like land or fresh-water ones, required to be implanted in an earthy or muddy soil, we should scarcely conceive how they could re sist the destructive action of those roaring waves which incessantly overturn and drive before them every obstacle that comes in their way, sweeps the bottom of the seas, and heaps upon the shores the debris of rocks. To struggle with impediments so powerful, marine plants would require a peculiar mode of existence: nature has therefore awarded them a more solid base than that of a mobile sand, continually tossed about by the impetuous movements of the waters; it has fixed their abode

upon the hardest bodies, upon stones and rocks, to which they adhere by a base of great tenacity, or rather are cramped by means of a sort of branched claw, very different from a root, although having its appearance. These claws are not destined to draw from a soil which they cannot penetrate, alimentary juices which are to be carried to the upper parts of these vegetables; for these parts, being entirely immersed in the same medium, equally absorb, by the whole of their surface, the principles of their nutrition, and we have not as yet been able to discover the ascent of any liquid, such as sap, &c. Marine plants have, besides a foliage which is plane or divided into filaments, of a pliant texture, a coriaceous or membranaceous structure, susceptible of accommodating itself to all the motions of the water. in which it is immersed, without receiving any injury.

Although their mode of fructification is still little known, it appears that their seeds, or what they have in place of them, are very glutinous; that they attach themselves indifferently to all solid bodies, and cover the rocks with a vegetation equally abundant, and not less agreeable than that of the swards which carpet our mountains. It is true they do not expand brilliant corollæ, nor fill the air with their perfumes, but they often present, in the form, variety and mixture of the colours of their foliage, an aspect not less seducing.

It would be difficult to say what are the circumstances favourable or hurtful to their multiplication; but if we examine the rocks which it is permitted us to approach, we shall find them covered with a rich vegetation. It is to be supposed that these plants, although placed in the same general medium, are, equally with terrestrial plants, subjected to the influence of localities, depths and temperature, since there are some which only shew themselves in certain seas, which are met with, for instance in the Atlantic, while they are not to be seen in the Mediterranean, which occur in the Indian Ocean, while they are denied to the frozen seas of the north, &c. Others grow at such depths that we are only acquainted with them by means of their fragments.

I shall not follow further in her great works, Nature incessantly occupied in laying everywhere the foundations of vegeta tion. What I have said will suffice to present an idea of all the

resources which she employs to overcome obstacles, and diffuse motion and life throughout. We have followed her in the plains, upon the mountains, in the moving sands, and in the very bosom of the waters. If we now descend into the cavities where the light never penetrates, we shall there find peculiar plants, destined to dwell in darkness, such as certain species of rhizomorphæ, byssi, &c. In short there are no substances, whether contained in the open air, or in the waters, laid open to the light, or concealed in the most obscure recesses, exposed to humidity or to dryness, which are not occupied by plants adapted for these different localities. The moulds attack all our alimentary provisions, when they are left undisturbed and kept in damp places; numerous fungi, enormous boleti, grow in the shade upon plants in a state of putrefaction; lichens and mosses penetrate the wrinkled bark of trees; a multitude of animals of a very inferior order, such as larvæ of insects, worms, mollusca, whether naked or testaceous, crustacea, arachnidæ, establish their abode in the midst of this growing vegetation; they deposit their offspring there, live in abundance, like our herds in the pastures, enjoy the coolness and the shade, like the great animals in their forests. In this manner is propagated the sublime work of creation in those organic beings which contribute, during their life, by their secretions, and after their death by their spoils, to the augmentation of vegetable earth, and of many other inorganic substances.

Observations made during a Visit to Madeira, and a Residence in the Canary Islands. By Baron LEOPOLD VON BUCH. (Continued from former volume, p. 380.)

AT this we were much surprised. We did not imagine we had climbed to such a height, and we thought that it was impossible to ascend so high in Madeira. The accounts of the height of Pico Ruivo, which is by far the highest mountain on the island, stood far below our calculation of the height of Toringas. Dr Thomas Heberden (a brother of Dr William Heberden, to whom we are indebted for the remarkable obser

vations upon the increasing quantity of rain accumulated near the surface, in other respects an accurate individual) mentions that he, by barometrical observations, according to De Luc's formula, had calculated the height of Pica Ruivo at 4825 French feet. The barometer was not observed by himself, however, but by some English travellers, whom he does not name. He does not give the barometrical height, but merely the result, (Phil. Trans. lv. 126). This measurement may, therefore, be considered somewhat doubtful. Two later observers, instead of removing this doubt, have only increased it. The celebrated Captain Sabine saw the barometer on the summit of Pico Ruivo on 13th June 1822, 23° In., 4.54 Lin. par. therm. 1o.8 R : In Funchal 7 feet above the sea, 28.6,-33,-13.1; which gives the mountain an elevation of 5011 French feet.

Bowdich had ascended the mountain about the same time, and had seen the barometer at a height of 22° In., 10°.7 Lin. par therm., 7.5 R: In the house of the Consul Veitch, at Funchal, 28.-5,6,-16.4. This house lies 145 feet above the sea; the top of the mountain is therefore 5788 French feet, 304 feet more than Cima de Toringa, according to one account, (Jameson's Edin. Journal, xviii. 317.) There can be no doubt of the greater height of Pico Ruivo; and there being little probability of error in the continued series of our observations, I consider that Bowdich's measurement, contained in his letter to Jameson, is to be preferred.

Towards the evening of Tuesday 2d May, we left Funchal and Madeira. The wind carried us tediously along. The captain, however, on the 4th, told us that he saw the Peak. He saw it with a seaman's eye from the tint of the atmosphere above it. It was not visible to us; but early on the 5th, Teneriffe was completely spread out before us. At the distance of about twenty-seven miles, the Peak rose above the clouds, vast and majestic; and the snow was seen lying upon its declivity, and descending almost to the woods; while the people were busily engaged with the wheat harvest, on the gently sloping shore of Tacaronte. At length Orotava appeared beneath the clouds of the Peak, as Frascati does from Rome, and a distinct stream of lava stretching from the Peak towards the

harbour, could be seen by the eye, among plants and layers of white pumice.

On 6th May, at 10 A. M., we landed at Puerto Orotava. To render our stay on this island ever worthy of remembrance, it was scarcely necessary to be admitted to the hospitality of (Barry and Bruce), one of the most intelligent, amiable, and polite families in the town. When evening recalled us from our excursions in the neighbourhood, we hastened home, to find there united every thing that genius, intelligence, fine feeling, and Spanish warmth of temperament, could produce. Having thus explored the woods above Villa Orotava, the rocks of St Ursula, Ria Lejo, La Rambla, the environs of Garachico and Icod, we at length, on the 18th May, undertook to ascend the Peak.

Being tolerably intimate with the works of other travellers, we did not stop by the way to discover new phenomena unobserved by others, but to discover some traces of what we found related in these old accounts. We hence expected, after leaving the beautiful chesnut wood above Villa Orotava, to meet with the woods of pines, which Humboldt supposed were certainly a new species, hitherto undescribed, (Rel i. 186.) We saw only the celebrated Pino del Dornajito, the only one that appeared the whole way. Still it is certain, that their way to the foot of the peak was through a thick wood of trees of this description. This was the case at the beginning of the last century; and according to the observation of Edens and P. Feuillé, the ascent in this wood, through pine trees of striking shape and size, was divided into several sections, the Pino de la Caravela, and higher, the Pino de la Merienda. These the destructive axe has not spared; and the Pino del Dornajito, the only one the whole way up, owes its preservation solely to the spring which it overshadows. At present there is no trace of the pine-trees, and the ground is covered with small bushes of heath and plants of fern. At present, we meet with point out the path; and

no object, which, like a pillar, could we perceive, with surprise, that we have spent a number of hours in climbing from the chesnuts to Portillo, by a road over which we do not appear to make the least progress, by reason of the uniformity of the objects around it.