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land vallies in calm weather, so long as the winds mingle no currents of air of a different temperature. It is at this season that one enjoys all the beauty of a landscape which, at the end of January, I never saw perfectly clear, except for a few days. The two round heads of the Silla appear at Caraccas almost under the same angle of elevation as the Pic of Teneriffe in the port of Orotava. The lower half of the mountain is clothed with a smooth turf; next comes the zone of evergreen shrubs, which a rosy light reflects at the flowering-time of the Befaria, the Alpine Rose-bay of equinoxial America. Above this woody zone rise two huge rocky masses in the -shape of cupolas. Destitute of vegetation, they increase by their nudity the apparent height of a mountain, which, in the temperate part of Europe, would scarcely be considered in the line of perpetual snow. It is with this imposing aspect of the Silla, and the rugged disposition of the ground to the north of the town, that are agreeably contrasted the cultivated region of the vale, and the smiling plains of Chacao, of Petera, and La Vega.'—581.

A tasto for literature is encouraged at Caraccas, and the inhabitants are particularly fond of music, which is cultivated with success, and which serves, as the cultivation of the fine arts seldom fails to do, to bring together the different classes of society; but the sciences have made little progress. It was only in the convent of St. Francis that our travellers met with a respectable old man, who had distinct notions on the state of modern astronomy; and he calculated almanacs for all the provinces of Venezuela. This great city had no printing press before 180G, when a Frenchman, of the name of Delpeche, introduced one.

In a journey to the summit of the peaked mountain of Silla, we have many curious and striking observations on the rocks, the vegetation, and the state of the atmosphere. Here, as afterwards among the Andes, the travellers sought in vain for a native rose-bush; and M. de Humboldt doubts if this charming plant is to be found in all South America, or even in the whole southern hemisphere. His elucidations on the distribution of plants, and the singular resemblance in the habit and physiognomy of plants under isothermal parallels, in regions the most distant from each other, are ingenious and interesting, but too long for us to give even an abstract of them. He deprecates all hypotheses on this subject, too lightly adopted by some, and declines substituting others, conceiving that the natural historian has performed his part in pointing out the facts and the order in which nature has distributed the vegetable forms. This is as it ought to be; and we heartily congratulate M. de Humboldt on his escape from the trammels of theory, which is at once the pride and the bane of science in the capital of France where he first imbibed it.

The view from the top of the Silla is thus described.

'Having gained the summit, we enjoyed, though but for a few

minutes,

minutes, the heavens in all their serenity. Our eye stretched over a vast extent of country, plunging at once upon the sea in the north, and upon the fertile valley of Caraccas in the south. The barometer stood at 30 inches 7. 6 lines; the temperature of the atmosphere was 13° 7'. We were at an elevation of thirteen hundred and fifty toises. An expanse of sea, of thirty-six leagues radius, is embraced in one view. Those who are apt to become dizzy on looking down great depths, should remain in the middle of the small flat on the summit of the eastern cupola of the Silla. The mountain is not remarkably high, being nearly eighty toises lower than that of Canigou; but what distinguishes it from all the mountains I have crossed, is its immense precipice on the side of the sea. The shore forms but a narrow edging; and, in looking from the top of the pyramid upon the houses of Caravellada, the wall-sided rocks, by an optical illusion of which I have often spoken, appear almost perpendicular. The true inclination of the slope appeared to me, by an accurate calculation, 53° 28'. The mean inclination of the Pic of Tenerifte is hardly 12° 30'. A precipice of six or seven miles, like that of the Silla of Caraccas, is a phenomenon much rarer than is imagined by those who traverse mountains without measuring their height, bulk, or declivity. Since the revival, in several parts of Europe, of experiments upon the fall of bodies, and upon their deflexion to the south-east, a wall-sided rock, two hundred and fifty toises of perpendicular height, has been sought in vain throughout all the Alps of Swisserland. The slope of Mount Blanc to the Allee Blanche does not make an angle even of 45°, although, in most geological works, Mount Blanc is described as cut straight down on the south.'—p. 608.

It was night when they reached, in their descent, the savanna, which is more than nine hundred toises in height.

'As there isscarcely any twilight between the tropics, perfect day-light is followed by sudden darkness. The moon was in the horizon: her face was covered from time to time by heavy clouds driven by a cold, impetuous wind. The sleep declivities, clothed with yellow, withered grass, were at one time wrapt in obscurity, then,suddenly illumined,they looked like precipices which the eye sought to fathom. We proceeded in a long file, endeavouring to assist each other with our hands, to prevent rolling down in case of stumbling. The guides who carried our instruments left us one by one to go and sleep in the mountain. Among those who remained, was a Congo negro, who excited my admiration by the skill with which he carried upon his head a large dipping needle, keeping it always in equilibrium, notwithstanding the great steepness of the rocks. The mist began to clear away from the bottom of the valley. The lights which we saw scattered beneath us produced a double illusion—the steeps seeming still more dangerous than they really were.and,during six hours of continual descent, we constantly fancied ourselves near the farm-houses at the foot of the Silla. We heard, very distinctly, human voices and the shrill tones of guitars. Generally speaking, so strong is the upward propagation of sound, that, in an aerostatic balloon, the barking of dogs may sometimes be heard at the height of three thousand toises.'—p. 6l6. . This last observation is very just. From the edge of the Table

Mountain, Mountain, which is three thousand six hundred feet high, and the upper part of which rises perpendicularly at the distance of about a mile from Cape Town, every noise made in the town, and even the word of command on the parade, may be distinctly heard. Shakspeare therefore is probably more correct when he describes the crows and choughs from Dover cliff to shew 'scarce so gross as beetles,' than when he says

'the murmuring surge

That on th' unnumbered idle pebbles chafe,
Can scarce be heard so high.'

The volume, concludes with some account of the attempts at working the,gold and silver mines of the Caraccas, which were soon abandoned from the slender indications of these metals, and the high price of labour; but M. de Humboldt thinks that the question whether the province of Venezuela possesses mines worthy of being worked is by no means decided; and that although in countries where labour is dearer, the cultivation of the soil demands unquestionably the first care of government, the example of New Spain sufficiently proves that the working of metals does not always injure the progress of agricultural industry. 'The highest cultivated plains of Mexico, (he says,) those which recal to the recollection of travellers the most beautiful fields of France and the south of Germany, extend from Silao towards the Villa de Leon: they border on the mines of Guanaxuato, which alone produce the sixth part of all the silver of the New World.'

We have been copious in our extracts, in order more fully to exhibit M. de Humboldt's manner of treating his subjects. Being less scientific than the former part of the narrative, this volume is better adapted for the general reader; and, as M. de Humboldt knows so well to communicate an interest to every subject which comes under his view, we have very little doubt that his remaining volumes, which will conduct his readers along the Oronoco, the Cordilleras of the Andes, and the elevated plains of Mexico, will rise in interest with the importance and grandeur of his subjecct.

Art. VII. A practical Inquiry into the Causes of the frequent Failure of the Operations of Depression, and of the Extraction of the Cataract, as usually performed; with the Description of a Series of neze and improved Operations, by the practice of which most of these Causes of Failure may he avoided. Illustrated by Tables of the comparative success of the new and old modes of practice. By Sir William Adams, &c. London. 1817. '•| ''HERE is less of the art of composition in this book than we -*- usually meet with in the present day. The title-page has in no .inconsiderable degree run away with the preface—and the decation with the subject and the supplement. The periods are,

Mi many instances, out of joint; the manner is too diffuse and desultory, and the pronoun of the first person somewhat more frequent in its appearance than is customary in the polished reserve of modern times. With all this, however, the work has a peculiar claim to attention, and we have read it with considerable interest. Its subject is highly important; its questionable points are discussed with great candour; it is enriched with the opinions and practice of the best and most skilful authorities of every country,' not ostentatiously paraded, but fairly brought forward and compared, for the purpose of stating their respective merits and defects, and of showing the necessity of some improvement in the best modes of operating for the cataract which have hitherto been devised; and it is rendered still more valuable by the author's ingenuous disclosure of the practice which he is well known to have applied with success to the blind pensioners of Greenwich Hospital, as well as in the private course of his professional engagements.

The definition of the disease called Cataract is thus given in the opening paragraph of the work:—

'The term cataract is of Greek derivation, and signifies an opacity either of the crystalline lens, its capsule, or the interstitial fluid contained between the lens and capsule, which is called the Humour Morgagni, (Humor MorgagniJ it having been first discovered by the eminent anatomist of that name. Cataract may exist in any of these parts separately, or they may all be at the same time opaque/ To which the author adds, (p. 4.) ' the capsule and lens are, however, much more frequently occupied by'disease than the humour morgagni.'

We suspect that a simple cataract of Morgagni's interstitial fluid is rather a speculative than an actual disease; one that possibly may exist, rather than one that has been actually detected and; described. Richter, so far as we are acquainted, is the only writer before Sir William Adams, who has ever noticed this species or variety; for at present we know not how to arrange it. The notice occurs, as in the volume before us, in the initiatory account of the disease, and is never touched upon or referred to afterwards. Nor do we recollect a single case of the kind described as an actual occurrence in any author whatever: and hence Plenck, who has made a very free use of Richter, and followed up the diseases of the eye through little less than six hundred distinct species, (to; say nothing of the numerous varieties into which each of these species is still further divided,) and who may therefore be conceived to have given all that is needful, has omitted the interstitial cataract altogether.*

It

• His definition being as follows.—' Cataracta—est czecitas, qua; ab opacitate lentis qrystaltintv, vel ejus capsule, proveuit.—Respectu sedis, quam opacitas tenet, dividitur

cataracta,

It is singular that the term cataract, though, as our author observes, of Greek derivation, and certainly of considerable antiquity, is not to be found either among the Greek or Roman writers; the first of whom called the disease apochysis (a.Ttlsyu<j\$) or hypochysis (u7ro';£u<n;)—and the latter suffusio, which is the name employed by Celsus. Cataracta, however, is in frequent use among the Arabiau authors, and is generally supposed to have been invented by Avicenna. That we derived it from the splendid caliphat of Bagdad there can be little doubt. The term cataract, however, does1 not exactly signify an opacity, as is stated in the definition before us, nor disturbance or confusion of the sense of vision, as is its common interpretation. Cataractes, or catarrhactes, (xarapaxTi); or xMTseppaxnjc,) whence the Latin cataracta, is a genuine Greek term, importing a gate or door, or the bar which fastens it and proves an impediment to its being opened; and, as the eyes were called by the Greek philosophers the portals or windows of the mind,—

Dicere porro oculos nullam rem cernere posse,
Sed per eos animum ut fortius spec tare reclusis,
Difficile est—

the elegant fancy of the Arabians applied the term cataracta to the disease before us, as forming a bar or shutter to those windows by which the mind obtains a view of external objects, or an external world.

One of the most difficult species of cataract to detect is that of the lenticular membrane or capsule, (the second of Plenck and of Sir William Adams,) when confined to its posterior part, or that immediately behind the lens itself, and which is hence, in a very considerable degree, concealed by it. From the depth of the opacity, covered by the healthy appearance and natural brilliancy of the lens, it is not surprizing that it should have puzzled many ophthalmists of considerable practice, and been mistaken by others for an amaurosis or gutta serena, and consequently, while admitting of cure, been abandoned as an intractable disease.

'The opacity of the anterior part of the capsule can at all times be easily distinguished; but the posterior opacity is not easily detected, and has been known to elude the careful examination of several very experienced oculists, by whom it has been mistaken for gutta serena; and, although this species of cataract is mentioned by authors, it may be doubted whether they were, in reality, practically, aware of its existence. Indeed, without the assistance of the belladonna, or some other application capable of dilating the pupil, which class of applica

cataracta, 1. In crystallinam, si ipsa lens crystallins est opaca. 2. In capsularem, quam alii membranaceam vocant, si capsular crystalline lamina anterior, vel posterior, vel utraque, opaca redditur. 3. In crjstallino-capsularem, si lens crystallina et ejus capsula simul opacautur.'

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