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to the idea of a chemical solution; and sound of living thing is hushed, and this idea is no way at variance with the nature, therefore, seems to utter a phenomena, that we daily observe in our

louder voice, only because no discordlaboratories. The waters of great rivers

ant sound mingles with her echoes ; contain carbonic acid ; and, were they even

and in the next place, it is supposed entirely pure, they would still be capable,

that the moisture and coolness of the in very great volumes, of dissolving some portions of oxyd, or those metallic hydrats,

air during night are still more efficient which are regarded as the least soluble.

causes of this phenomenon and this The mud of the Nile, which is the sedi.

is the solution which even philosoment of the matters that the river holds phic minds have been accustomed suspended, is destitute of manganese ; but to give. Let us now hear Mr Humcontains, according to the analysis of Mr boldt on the fact; and without preRegnault

, six parts in a hundred of oxyd suming to answer for the justness of of iron; and its colour, at first black, chan.

his theory, we shall at least be forges to yellowish brown by desiccation and

ced to confess that it is ingenious che contact of air. The mud consequently

and plausible.
is not the cause of the black crusts on the
rocks of Syene. Mr Berzelius had the

66 The inhabitants of Atures and Maygoodness, at my request, to examine these pures, whatever the missionaries may have crusts, and recognized in them, as in those

asserted in their works, are not more struck of the granites of the Oroonoko and Rio with deafness by the noise of the great ca. Congo, the union of iron and manganese.

taracts, than the Catadupes of the Nile. This celebrated chemist thinks, that the ri. When this noise is heard in the plain that vers do not take up these oxyds from the surrounds the mission, at the distance of soil orer which they flow, but derive them more than a league, you seem to be near from their subterraneous sources, and de

a coast skirted hy reefs and breakers. The posit them on the rocks in the manner of noise is three times as loud by night as by cementation, by the action of particular af- day, and gives an inexpressible charm to finities

, perlaps by that of the potash of the these solitary scenes. What can be the feldspar. A long residence at the cataracts

cause of this increased intensity of sound of the Oroonoko, the Nile, and the Rio in a desert, where nothing seems to interCongo, and an examination of the circum- rupt the silence of nature? The velocity of stances that accompany this phenomenon the propagation of sound, far from augof coloration, could alone lead to the com- menting, decreases with the lowering of the plete solution of the problem we have dis- temperature. The intensity diminishes in cussed. Is this phenomenon independent air agitated by a wind, which is contrary of the nature of the rocks? I shall content

to the direction of the sound; it diminishmyself with observing in general, that nei.

es also by dilatation of the air, and is weakther the granitic masses remote from the

er in the higher than in the lower regions ancient bed of the Oroonoko, but exposed of the atmosphere, where the number of during the rainy season to the alternations particles of air in motion is greater in the of heat and moisture, nor the granitic rocks

same radius. The intensity is the same bathed by the brownish waters of the Rio in dry air, and in air mingled with vaNegro, assume the appearance of meteoric pours; but it is feebler in carbonic acid stones. The Indians say, that the rocks gas, than in mixtures of azote and oxygen. ate black only where the waters are white.' From these facts, which are all we know They ought perhaps to add, where the with any certainty, it is difficult to explain waters acquire great swiftness, and strike

a phenomenon observed near every cascade with force against the rocks of the banks in Europe, and which, long before our arCementation seems to explain why the rival in the village of Atures, had struck crusts augment so little in thickness." the missionary and the Indians. The noc

pp. 20–24. turnal temperature of the atmosphere is 3°

less than the temperature of the day; at The next speculation relates to a fact the same time the apparent humidity augwhich has long been known to those ments at night, and the mist that covers who dwell in the neighbourhood of the cataracts becomes thicker. We have falls of water, and which has often just seen, that the hygroscopic state of the been accounted for on principles which air has no influence on the propagation of our author controverts. The fact is, the sound, and that the cooling of the air that the noise of a cataract is common

diminishes its swiftness. ly prodigiously increased in intensity

“ It may be thought, that, even in pladuring the night. The principles sects, the song of birds, the rustling of

ces not inhabited by man, the hum of inwhich naturally suggest themselves as leaves agitated by the feeblest winds, occaaccounting for this fact are, in the sion during the day a confused noise, which first place, the increased stillness of we perceive the less because it is uniform, the air during the night, when every and constantly strikes the car. Now this

noise, however slightly perceptible it may almost rest on the authority of an ancient be, may diminish the intensity of a louder philosopher, whom the moderns continue noise ; and this diminution may cease, if to treat with disdain, though the most disduring the calm of the night the song of tinguished zoologists have long rendered birds, the hum of insects, and the action of ample justice to the sagacity of his obserthe wind upon the leaves, be interrupted. vations. • Why,' says Aristotle in his cuBut this reasoning, even admitting its rious book of Problems, “ why is sound justness, can scarcely be applied to the fo- better heard during the night? Because rests of the Oroonoko, where the air is there is more calmness on account of the constantly filled by an innumerable quan- absence of caloric, ( of the hottest.) This tity of moschettoes, where the hum of in- absence renders every thing calmer, for the sects is much louder by night than by day, sun is the principle of all movement.' and where the breeze, if ever it be felt, Aristotle had no doubt a vague presenti. blows only after sunset.

ment of the cause of the phenomenon ; but “ I rather think, that the presence of he attributes to the motion of the atmothe sun acts upon the propagation and in. sphere, and the shock of the particles of tensity of the sound by the obstacles, which air, what seems to be rather owing to abthey find in the currents of air of different rupt changes of density in the contiguous density, and the partial undulations of the strata of air.” pp. 67–72. atmosphere caused by the unequal heating of Cifferent parts of the soil. İn calm air, The scenery of the Oroonoko seems, whether it be dry, or mingled with vesicu- from the descriptions of our traveller, lar vapours equally distributed, the sono to be often in the highest degree imrous undulation is propagated without diffi- pressive and sublime, and its cataracts culty. But when the air is crossed in every have a character of majesty and of direction by small currents of hotter air, continuous grandeur which is not the sonorous undulation is divided into two undulations, where the density of the me presented by similar rivers in any dium changes abruptly; partial echoes are other quarter of the globe. The fol formed, that weaken the sound, because one lowing description of the cataract of of the streams comes back upon itself; and Maypures, and also of the general those divisions of undulations take place, character of tropical scenery, is exceedof which Mr Poisson has recently devel. ingly striking. oped the theory with great sagacity. It is not therefore the movement of the particles “ To take in at one view the grand cha. of air from below to ahove in the ascend. racter of these stupendous scenes, the specing current, or the small oblique currents, tator must be stationed on the little moun. that we consider as opposing by a shock tain of Manimi, a granitic ridge, that rises the propagation of the sonorous undula. from the Savannah, north of the church of tions. A shock, given to the surface of a the mission, and is itself only a continualiquid, will form circles around the centre tion of the steps, of which the randalito of of percussion, even when the liquid is agi. Manimi is composed. We often visited tated. Several kinds of undulations may this mountain, for we were never weary of cross each other in water, as in air, without the view of this astonishing spectacle, conbeing disturbed in their propagation ; little cealed in one of the most remote corners of movements may ride over each other, and the earth. Arrived at the summit of the the real cause of the less intensity of sound rock, the eye suddenly takes in a sheet of during the day appears to be the interrup. foam, extending a whole mile. Enormous tion of homogeneity in the elastic medium. masses of stone, black as iron, issue from During the day, there is a sudden inter. its bosom. Some are paps grouped in ruption of density, wherever small stream- pairs, like basaltic hills; others resemble lets of air of a high temperature rise over towers, strong castles, and ruined build. parts of the soil unequally heated. The ings. Their gloomy tint contrasts with sonorous undulations are divided, as the the silvery splendour of the foam. Every rays of light are refracted, and form the rock, every islet is covered with vigorous mirage (looming) wherever strata of air of trees, collected in clusters. At the foot of unequal density are contiguous. The pro- those paps, as far as the eye can reach, a pagation of sound is altered, when a stra. thick vapour is suspended over the river, tum of hydrogen gas is made to rise in a and through this whitish fog the tops of tube closed at one end above a stratum of the lofty palm-trees shoot up. What name atmospheric air ; and Mr Biot has well shall we give to these majestic plants? I explained by the interposition of bubbles suppose them to be the vadgiui, a new spe. of carbonic acid gas, why a glass filled with cies of the genus oreodoxa, the trunk of Champagne wine is little sonorous so long which is more than eighty feet high. The as the gas is evolved, and continues to pass leafy plume of this palm-tree had a brilthrough the strata of the liquid.

liant lustre, and rises almost straight to“ În announcing these ideas, I might ward the sky. At every hour of the day

the sheet of foam displaya different aspects. forms in different hemispheres and in Sometimes the hilly islands and the palm- remote countries, by referring all of trees project their broad shadows, some- them to varieties of climate and of soil; times the rays of the setting sun are re- although these varieties are often so fracted in the humid cloud, that shrouds great as to be very inadequately acthe cataract Coloured arcs are formeal, counted for upon this principle. and vanish and appear again alternately; Those who love what is sound' in light sport of the air, their images wave above the plain.

philosophy, will therefore be pleased “ Such is the character of the landscape with the following most just observadiscovered from the top of the mountain

tions. of Manimi, which no traveller has yet described. I do not hesitate to repeat, that

Every hemisphere produces plants of

a different species; and it is not by the dineither time, nor the view of the Cordilleras, nor any abode in the temperate

vallies versity of climates that we can attempt to of Mexico, have effaced from my mind the explain why equinoctial Africa has no powerful impression of the aspect of the why the calceolariæ are found only in the

laurineæ, and the New World no heaths ; cataracts

. When I read a description of southern hemisphere ; why the birds of the those places in India, that are embellished continent of India glow with colours less by running waters and a vigorous vegetation, my imagination retraces a sea of foam splendid than the birds of the hot parts of

pecuand palm-trees, the tops of which rise a America; finally, why the tiger is

liar to Asia, and the ornithorhincus to New bove a stratum of vapour. The majestic scenes of nature, like the sublime works of Holland. In the vegetable

as well as in the poetry and the arts, leave remembrances bution of the species are among the num

animal kingdom, the causes of the distrithat are incessantly awakening, and through the whole of life mingle with all our feel- ber of mysterics,

which natural philosophy

cannot reach. This science is not occuings of what is grand and beautiful.

" The calm of the atmosphere, and the pied in the investigation of the origin of tumultuous movement of the waters, pro

beings, but of the laws according to which duce a contrast peculiar to this zone. 'Here they are distributed on the globe. It exno breath of wind ever agitates the foliage,

amines the things that are, the co-existno cloud veils the splendour of the azure

ence of vegetable and animal forms in each vault of Heaven ; a great mass of light is latitude, at different heights, and at differdiffused in the air, or the earth strewn

ent degrees of temperature ; it studies the

relations under which particular organizawith plants with glossy leaves, and on the bed of the river, which extends far as the tiplied, or modified; but it approaches

tions are more vigorously developed, muleye can reach. This appearance surprises not problems, the solution of which is imthe traveller born in the north of Europe. possible, since they touch the origin, the The idea of wild scenery, of a torrent rushing from rock to rock, is linked in his ima- add, that the attempts which have been

first existence of a germe of life. We may gination with that of a climate, where the noise of the tempest is mingled with the made, to explain the distribution of vasound of the cataracts; and where, in a

rious species on the globe by the sole in

fluence of climate, date at a period when gloomy and misty day, sweeping clouds physical geography was still in its infancy; seem to descend into the valley, and rest

when, recurring incessantly to pretended upon the tops of the pines. The land

contrasts between the two worlds, it was scape of the tropics in the low regions of imagined, that the whole of Africa and of the continents has a peculiar physiognomy, America resembled the deserts of Egypt something of greatness and repose, which and the marshes of Cayenne. At present, it preserves even where one of the elements

when men judge of the state of things not is struggling with invincible obstacles. Near the equator, hurricanes and tempests positive knowledge, it is ascertained, that

trom one type arbitrarily chosen, but from belong to islands only, to deserts destitute the two continents in their immense ex. of plants, and to those spots, 'where parts tent contain countries that are altogether of the atmospliere repose upon surfaces, analogous. There are regions of America from which the radiation of heat is very different." pp. 137–140.

as barren and burning as the interior of

Africa. The islands that produce the We have of late been much pleased spices of India are scarcely remarkable for with the sober cast which many spe

their dryness; and it is not on account of culations have assumed, that but a

the humidity of the climate, as it has been few years ago were remarkable only Continent is deprived of those fine species

affirmed in recent works, that the New for extravagaree. It was then, and of laurinex and myristicæ, which are found had been for ages, a favourite theory united in one little corner of the earth in to account for the very various ap- the Archipelago of India. For some years pearances of vegetation and of animal past the real cinnamon has been cultivated

FOL. IX.

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with success in several parts of the New ders, while the black rivers have white. In Continent; and a zone that produces the fact, the shores of the Guainia, known to coumarouna, the vanilla, the pucheri, the the Europeans by the name of the Rio Ne. pine-apple, the myrtus pimenta, the bal gro, frequently exhibit masses of quartz sam of tolu, the myroxylon peruvianum, issuing from granite, and of a dazzling the crotons, the citrosmas, the pejoa, the whiteness. The waters of the Mataveni, incienso of the Silla of Caraccas, the que

when examined in a glass, are pretty reme, the pancratium, and so many ma wliite; those of the Atabapo retain a slight jestic liliaceous plants, cannot be consider. tinge of yellowish-brown. When the least ed as destitute of aromatics. Besides, a breath of wind agitates the surface of these dry air favours the developement of the aro black rivers, they appear of a fine grass matic, or exciting properties, only in cer. green, like the lakes of Switzerland. In tain specics of plants. The most cruel the shade, the Zaina, the Atabapo, and the poisons are produced in the most humid Guainia, are as dark as coffee grounds. zone of America ; and it is precisely un These phenomena are so striking, that the der the influence of the long rains of the Indians every where distinguish the waters tropics, that the American pimento, cap. by black and white. The former have sicum baccatum, the fruit of which is often often served me for an artificial horizon ; as caustic and fiery as Indian pepper, ve they reflect the image of the stars with ad. getates best. From the whole of these mirable clearness. considerations it follows, Ist, That the New The colour of the waters of springs Continent possesses spices, aromatics, and rivers, and lakes, ranks among those phy. very active vegetable poisons, that are pe- sical problems, which it is difficult, if not culiar to itself, differing specifically from impossible, to solve by direct experiments those of the ancient world ; 2dly, That the

The tints of reflected light are generally primitive distribution of species in the tor very different from the tints of transmitted rid zone cannot be explained by the in light; particularly when the transmission Auence of climate solely, or by the distri. takes place through a great portion of bution of temperature, which we observe

fluid. "If there were no absorption of rays, in the present etate of our planet ; but that the transmitted light would be of a colour this difference of climates leads us to per complementary to that of the reflected ceive, why a given type of organization de light; and in general we judge ill of transvelopes itself more vigorously in such or mitted light, by filling with water shal. such local circumstances. We can con low glass with a parrow aperture. In a ceive, that a small number of the families river the colour of the reflected light comes of plants, for instance the musaceæ and to us always from the interior strata of the the palms, cannot belong to very cold re fluid, and not from the upper stratum. gions, on account of their internal struc 6 Some celebrated naturalists, who have ture, and the importance of certain organs; examined the purest waters of the glaciers, but we cannot explain why no one of the and those which flow from mountains cofamily of melastomas vegetates north of vered with perpetual snows, where the the parallel of thirty degrees, or why no earth is destitute of the relics of vegetation, rose-tree belongs to the southern hemi. have thought, that the proper colour of sphere. Analogy of climates is often found water might be blue or green. Nothing, in the two continents, without identity of in fact, proves, that water is by nature productions." pp. 186_183.

white, and that we must always admit the

presence of a colouring principle, when wa. We have already noticed the rocks ter viewed by reflection is coloured. In which are covered with a black crust. the rivers that contain a colouring princiThe following quotation relates to a ple, this principle is generally so little in phenomenon of the rivers which is at quantity,

that it eludes all chemical releast as wonderful.

search. The tints of the ocean seem often

to depend neither on the nature of the bote 66 At the mouth of the Rio Zama we en: tom, nor on the reflection of the sky on the tered a class of rivers that merits great at clouds. It is said, a great naturalist, Sir tention. The_Zama, the Mataveni, the Humphry Davy, thinks, that the tints of Atabapo, the Tuamini, the Temi, and the different seas may very likely be owing to Guainia, are uguns negras, that is, their different proportions of iodin. waters, seen in a large body, appear brown “ On consulting the geographers of anlike coffee, or of a greenish black. These tiquity we find, that the Greeks were waters notwithstanding are the most beau. struck by the blue waters of Thermopylæ, tiful, the clearest, and the most agreeable the red waters of Joppa, and the black to the taste. I have observed above, that waters of the hot-baths of Astyra, opposite the crocodiles, and, if not the Zancudoes, Lesbos. Some rivers, the Rhone, for inat least the moschettoes, generally shun the stance, near Geneva, have a decidedly blue black waters. The people assert, too, that colour. It is said, that the snow waters, these waters do not embrown the rocks ; in the Alps of Switzerland, are sometimes and that the white rivers lare black bor. of an emerald green approaching to grass

ceæ.

green. Several lakes of Savoy and of Pe- open savannahs, that extend from the Men ru have a brown colour approaching black. ta beyond the Guaviare toward the Caquc. Most of these phenomena of coloration are ta. In a voyage which I made with Mr observed in waters that are believed to be de Montufar from the port of Guayaquil the purest, and it is rather from reasonings to Bodegas de Babaojo, at the period of founded on analogy, than from any direct the great inundations; I was struck by the analysis, that we may throw some light on analogy of colour displayed by the vast saso uncertain a matter. In the vast system vannahs of the Invernadero del Gurzal and of rivers which we have traversed, (and this of Lagartero, and the aspect of the Rio fact appears to me striking,) the black, wa Negro and the Atabapo. These savan. ters are principally restricted to the equa- nahs, partly inundated during three torial bund. They begin to be found a months, are composed of paspalum, ebout five degrees of north latitude; and a. riochloa, and several species of cyperabound thence to beyond the equator as far We sailed on waters that were from as about two degrees of south latitude four to five feet deep; their temperature The mouth of the Rio Negro is indeed in was by day from 330 to 34o of the centithe latitude of 3° 9°; but in this interval grade thermometer ; they exhaled a strong the black and white waters are so singu. smell of sulphuretted hydrogen, to which, larly mingled in the forests and the savan. no doubt, some rotten plant of arum and nahs, that we know not to what cause the heliconia, that swam on the surface of the coloration of the waters must be attributed. pools, contributed. The waters of LagarThe waters of the Cassiquiare, which fall tero were of a golden yellow by transmit. into the Rio Negro, are as white as those ted, and coffee brown by reflucted light. of the Oroonoko, from which it issues. Of They are, no doubt, coloured by a carburet two tributary streams of the Cassiquiare of hydrogen. An analogous phenomenon very near each other, the Siapa and the is observed in the dunghill waters prepared Pacimony, one is white, the other black. by our gardeners, and in the waters that

“ When the Indians are interrogated issue from bogs. May we not also admit, respecting the causes of these strange co that it is a mixture of carbon and hydrolorations, they answer, as questions in na gen, an extractive vegetable matter, that tural philosophy or physiology are some colours, the black rivers, the Atabapo, the times answered in Europe, by repeating Zama, the Mataveni, and the Guainia ? the fact in other terms. If you address The frequency of the equatorial rivers conyourself to the missionaries, they reply, as tributes, no doubt, to this coloration, by if they had the most convincing proofs of filtrations through a thick wad of grasses. their assertion, the waters are coloured I suggest these ideas only in the form of a by washing the roots of the sarsaparilla.” doubt. The colouring principle seems to The smilaceæ, no doubt, abound on the be in very little abundance ; for I observed, banks of the Rio Negro, the Pacimony, that the waters of the Guainia or Rio Ne. and the Cababury; their roots, macerated gro, when subjected to ebullition, do not in the water, yield an extractive matter, become brown like other fluids charged that is brown, bitter, and mucilaginous ; with carburets of hydrogen." but how many tufts of smilax have we

pp. 185-191. seen in places, where the waters were entirely white!' In the marshy forest which

The following relation is of a very we traversed, to convey our canoe from the different kind from any we have yet Rio Tuaminí to the C'anno Pimichin and quoted, and gives an affecting picture the Rio Negro, why, in the same soil, did both of the miseries of savage life, we ford alternately rivulets of black and and of the power of those natural inwhite water? Why was no river ever stincts which bind the heart of wofound white near its springs, and black in man to the children which she has the lower part of its course? I know not born. Speaking of his passage up one whether the Rio Negro preserve its yellow of the rivers, our traveller thus proish brown colour as far as its mouth, not. ceeds. withstanding the great quantity of white water it receives from the Cassiquiare and “ Before we reached its confluence, a the Rio Blanco. Mr. de la Condamine, granitic hunmock, that rises on the westnot having seen this river north of the ern bank, near the mouth of the Guasa. equator, could not judge of the difference cavi, fixed our attention ; it is called the of colour.

Rock of the Guahiba Woman, or the Rock * Although, on account of the abund of the Mother, Piedra de la Mudre. We ance of the rivers, vegetation is more vi- inquired the cause of so singular a denugorous close to the equalor than eight or mination. Father Zea could not satisfy ten degrees north or south, it cannot be our curiosity ; but some weeks after, ano affirmed, that the rivers with black waters ther missionary, one of the predecessors of rise principally in the most shady and this ecclesiastic, whom we found settlled at thickest forests. On the contrary, a great San Fernando as president of the missions, number of the aguas negras come from the related to us an event, which I recorded in

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