AFTER having been twice driven back by heavy southwesterngales, Her Majesty's ship Beagle, a ten-gunbrig, under the command of Captain Fitz Roy, R. N.,sailed from Devonport on the 27th of December, 1831. Theobject of the expedition was to complete the survey ofPatagonia and Tierra del Fuego, commenced under Captain Kingin 1826 to 1830, -- to survey the shores of Chile, Peru, andof some islands in the Pacific -- and to carry a chain ofchronometrical measurements round the World. On the 6thof January we reached Teneriffe, but were prevented landing,by fears of our bringing the cholera: the next morningwe saw the sun rise behind the rugged outline of the GrandCanary island, and suddenly illuminate the Peak of Teneriffe,whilst the lower parts were veiled in fleecy clouds. Thiswas the first of many delightful days never to be forgotten.On the 16th of January, 1832, we anchored at Porto Praya,in St. Jago, the chief island of the Cape de Verd archipelago.

The heraldic ornaments were the only things in this retiredplace that reminded us of Europe. The church or chapelformed one side of a quadrangle, in the middle of which alarge clump of bananas were growing. On another sidewas a hospital, containing about a dozen miserable-lookinginmates.

We returned to the Venda to eat our dinners. A considerablenumber of men, women, and children, all as black asjet, collected to watch us. Our companions were extremelymerry; and everything we said or did was followed by theirhearty laughter. Before leaving the town we visited thecathedral. It does not appear so rich as the smaller church,but boasts of a little organ, which sent forth singularlyinharmonious cries. We presented the black priest with a fewshillings, and the Spaniard, patting him on the head, said,with much candour, he thought his colour made no greatdifference. We then returned, as fast as the ponies wouldgo, to Porto Praya.

Another day we rode to the village of St. Domingo, situatednear the centre of the island. On a small plain whichwe crossed, a few stunted acacias were growing; their topshad been bent by the steady trade-wind, in a singularmanner -- some of them even at right angles to their trunks.The direction of the branches was exactly N. E. by N., and S. W.by S., and these natural vanes must indicate the prevailingdirection of the force of the trade-wind. The travelling hadmade so little impression on the barren soil, that we heremissed our track, and took that to Fuentes. This we didnot find out till we arrived there; and we were afterwardsglad of our mistake. Fuentes is a pretty village, with a smallstream; and everything appeared to prosper well, excepting,indeed, that which ought to do so most -- its inhabitants.The black children, completely naked, and looking verywretched, were carrying bundles of firewood half as big astheir own bodies.

Near Fuentes we saw a large flock of guinea-fowl --probably fifty or sixty in number. They were extremelywary, and could not be approached. They avoided us, likepartridges on a rainy day in September, running with theirheads cocked up; and if pursued, they readily took to thewing.

The scenery of St. Domingo possesses a beauty totallyunexpected, from the prevalent gloomy character of the restof the island. The village is situated at the bottom of avalley, bounded by lofty and jagged walls of stratified lava.The black rocks afford a most striking contrast with thebright green vegetation, which follows the banks of a littlestream of clear water. It happened to be a grand feast-day,and the village was full of people. On our return we overtooka party of about twenty young black girls, dressed inexcellent taste; their black skins and snow-white linen beingset off by coloured turbans and large shawls. As soon aswe approached near, they suddenly all turned round, andcovering the path with their shawls, sung with great energya wild song, beating time with their hands upon their legs.We threw them some vintems, which were received withscreams of laughter, and we left them redoubling the noiseof their song.

One morning the view was singularly clear; the distantmountains being projected with the sharpest outline on aheavy bank of dark blue clouds. Judging from the appearance,and from similar cases in England, I supposed that theair was saturated with moisture. The fact, however, turnedout quite the contrary. The hygrometer gave a differenceof 29.6 degs., between the temperature of the air, and thepoint at which dew was precipitated. This difference wasnearly double that which I had observed on the previousmornings. This unusual degree of atmospheric dryness wasaccompanied by continual flashes of lightning. Is it not anuncommon case, thus to find a remarkable degree of aerialtransparency with such a state of weather?

The geology of this island is the most interesting part ofits natural history. On entering the harbour, a perfectlyhorizontal white band, in the face of the sea cliff, may be seenrunning for some miles along the coast, and at the height ofabout forty-five feet above the water. Upon examinationthis white stratum is found to consist of calcareous matterwith numerous shells embedded, most or all of which nowexist on the neighbouring coast. It rests on ancient volcanicrocks, and has been covered by a stream of basalt, whichmust have entered the sea when the white shelly bed waslying at the bottom. It is interesting to trace the changesproduced by the heat of the overlying lava, on the friablemass, which in parts has been converted into a crystallinelimestone, and in other parts into a compact spotted stoneWhere the lime has been caught up by the scoriaceous fragmentsof the lower surface of the stream, it is converted intogroups of beautifully radiated fibres resembling arragonite.The beds of lava rise in successive gently-sloping plains,towards the interior, whence the deluges of melted stonehave originally proceeded. Within historical times, no signsof volcanic activity have, I believe, been manifested in anypart of St. Jago. Even the form of a crater can but rarelybe discovered on the summits of the many red cindery hills;yet the more recent streams can be distinguished on thecoast, forming lines of cliffs of less height, but stretchingout in advance of those belonging to an older series: theheight of the cliffs thus affording a rude measure of the ageof the streams.

I was much interested, on several occasions, by watchingthe habits of an Octopus, or cuttle-fish. Although commonin the pools of water left by the retiring tide, these animalswere not easily caught. By means of their long arms andsuckers, they could drag their bodies into very narrow crevices;and when thus fixed, it required great force to removethem. At other times they darted tail first, with the rapidityof an arrow, from one side of the pool to the other, at thesame instant discolouring the water with a dark chestnut-brownink. These animals also escape detection by a veryextraordinary, chameleon-like power of changing their colour.They appear to vary their tints according to the natureof the ground over which they pass: when in deep water,their general shade was brownish purple, but when placed onthe land, or in shallow water, this dark tint changed into oneof a yellowish green. The colour, examined more carefully,was a French grey, with numerous minute spots of brightyellow: the former of these varied in intensity; the latterentirely disappeared and appeared again by turns. Thesechanges were effected in such a manner, that clouds, varyingin tint between a

This cuttle-fish displayed its chameleon-like power bothduring the act of swimming and whilst remaining stationaryat the bottom. I was much amused by the various arts toescape detection used by one individual, which seemed fullyaware that I was watching it. Remaining for a time motionless,it would then stealthily advance an inch or two, like acat after a mouse; sometimes changing its colour: it thusproceeded, till having gained a deeper part, it darted away,leaving a dusky train of ink to hide the hole into which ithad crawled.

While looking for marine animals, with my head abouttwo feet above the rocky shore, I was more than once salutedby a jet of water, accompanied by a slight grating noise. Atfirst I could not think what it was, but afterwards I foundout that it was this cuttle-fish, which, though concealed in ahole, thus often led me to its discovery. That it possessesthe power of ejecting water there is no doubt, and it appearedto me that it could certainly take good aim by directing thetube or siphon on the under side of its body. From thedifficulty which these animals have in carrying their heads,they cannot crawl with ease when placed on the ground. Iobserved that one which I kept in the cabin was slightlyphosphorescent in the dark.

In crossing the Atlantic we hove-toduring the morning of February 16th, close to the island ofSt. Paul's. This cluster of rocks is situated in 0 degs. 58'north latitude, and 29 degs. 15' west longitude. It is 540miles distant from the coast of America, and 350 from the islandof Fernando Noronha. The highest point is only fifty feet abovethe level of the sea, and the entire circumference is underthree-quarters of a mile. This small point rises abruptly outof the depths of the ocean. Its mineralogical constitutionis not simple; in some parts the rock is of a cherty, in othersof a felspathic nature, including thin veins of serpentine. Itis a remarkable fact, that all the many small islands, lyingfar from any continent, in the Pacific, Indian, and AtlanticOceans, with the exception of the Seychelles and this littlepoint of rock, are, I believe, composed either of coral or oferupted matter. The volcanic nature of these oceanic islandsis evidently an extension of that law, and the effect of thosesame causes, whether chemical or mechanical, from which itresults that a vast majority of the volcanoes now in actionstand either near sea-coasts or as islands in the midst of thesea.

The rocks of St. Paul appear from a distance of a brilliantlywhite colour. This is partly owing to the dung of avast multitude of seafowl, and partly to a coating of a hardglossy substance with a pearly lustre, which is intimatelyunited to the surface of the rocks. This, when examinedwith a lens, is found to consist of numerous exceedinglythin layers, its total thickness being about the tenth of aninch. It contains much animal matter, and its origin, nodoubt, is due to the action of the rain or spray on the birds'dung. Below some small masses of guano at Ascension, andon the Abrolhos Islets, I found certain stalactitic branchingbodies, formed apparently in the same manner as the thinwhite coating on these rocks. The branching bodies so closelyresembled in general appearance certain nulliporae (a familyof hard calcareous sea-plants), that in lately looking hastilyover my collection I did not perceive the difference. Theglobular extremities of the branches are of a pearly texture,like the enamel of teeth, but so hard as just to scratch plate-glass. I may here mention, that on a part of the coast ofAscension, where there is a vast accumulation of shelly sand,an incrustation is deposited on the tidal rocks by the waterof the sea, resembling, as represented in the woodcut, certaincryptogamic plants (Marchantiae) often seen on dampwalls. The surface of the fronds is beautifully glossy; andthose parts formed where fully exposed to the light are of ajet black colour, but those shaded under ledges are only grey.I have shown specimens of this incrustation to severalgeologists, and they all thought that they were of volcanicor igneous origin! In its hardness and translucency -- inits polish, equal to that of the finest oliva-shell -- in thebad smell given out, and loss of colour under the blowpipe -- itshows a close similarity with living sea-shells. Moreover, insea-shells, it is known that the parts habitually covered andshaded by the mantle of the animal, are of a paler colourthan those fully exposed to the light, just as is the case withthis incrustation. When we remember that lime, either as aphosphate or carbonate, enters into the composition of thehard parts, such as bones and shells, of all living animals, itis an

We found on St. Paul's only two kinds of birds -- thebooby and the noddy. The former is a species of gannet,and the latter a tern. Both are of a tame and stupiddisposition, and are so unaccustomed to visitors, that I couldhave killed any number of them with my geological hammer.The booby lays her eggs on the bare rock; but the tern makesa very simple nest with seaweed. By the side of many ofthese nests a small flying-fish was placed; which I suppose,had been brought by the male bird for its partner. It wasamusing to watch how quickly a large and active crab(Graspus), which inhabits the crevices of the rock, stole thefish from the side of the nest, as soon as we had disturbedthe parent birds. Sir W. Symonds, one of the few personswho have landed here, informs me that he saw the crabsdragging even the young birds out of their nests, and devouringthem. Not a single plant, not even a lichen, growson this islet; yet it is inhabited by several insects andspiders. The following list completes, I believe, theterrestrial fauna: a fly (Olfersia) living on the booby, anda tick which must have come here as a parasite on the birds;a small brown moth, belonging to a genus that feeds on feathers;a beetle (Quedius) and a woodlouse from beneath the dung; andlastly, numerous spiders, which I suppose prey on these smallattendants and scavengers of the water-fowl. The often repeateddescription of the stately palm and other noble tropicalplants, then birds, and lastly man, taking possession ofthe coral islets as soon as formed, in the Pacific, is probablynot correct; I fear it destroys the poetry of this story, thatfeather and dirt-feeding and parasitic insects and spidersshould be the first inhabitants of newly formed oceanicland.

The smallest rock in the tropical seas, by giving a foundationfor the growth of innumerable kinds of seaweed andcompound animals, supports likewise a large number of fish.The sharks and the seamen in the boats maintained a constantstruggle which should secure the greater share of theprey caught by the fishing-lines. I have heard that a rocknear the Bermudas, lying many miles out at sea, and at aconsiderable depth, was first discovered by the circumstanceof fish having been observed in the neighbourhood.

FERNANDO NORONHA, Feb. 20th. -- As far as I was enabledto observe, during the few hours we stayed at this place, theconstitution of the island is volcanic, but probably not of arecent date. The most remarkable feature is a conical hill,about one thousand feet high, the upper part of which isexceedingly steep, and on one side overhangs its base. Therock is phonolite, and is divided into irregular columns. Onviewing one of these isolated masses, at first one is inclinedto believe that it has been suddenly pushed up in a semi-fluidstate. At St. Helena, however, I ascertained that somepinnacles, of a nearly similar figure and constitution, hadbeen formed by the injection of melted rock into yieldingstrata, which thus had formed the moulds for these giganticobelisks. The whole island is covered with wood; but fromthe dryness of the climate there is no appearance of luxuriance.Half-way up the mountain, some great masses of thecolumnar rock, shaded by laurel-like trees, and ornamentedby others covered with fine pink flowers but without a singleleaf, gave a pleasing effect to the nearer parts of the scenery.

BAHIA, OR SAN SALVADOR. BRAZIL, Feb. 29th. -- The dayhas passed delightfully. Delight itself, however, is a weakterm to express the feelings of a naturalist who, for the firsttime, has wandered by himself in a Brazilian forest. Theelegance of the grasses, the novelty of the parasitical plants,the beauty of the flowers, the glossy green of the foliage,but above all the general luxuriance of the vegetation, filledme with admiration. A most paradoxical mixture of soundand silence pervades the shady parts of the wood. The noisefrom the insects is so loud, that it may be heard even in avessel anchored several hundred yards from the shore; yetwithin the recesses of the forest a universal silence appearsto reign. To a person fond of natural history, such a dayas this brings with it a deeper pleasure than he can ever hopeto experience again. After wandering about for some hours,I returned to the landing-place; but, before reaching it, Iwas overtaken by a tropical storm. I tried to find shelterunder a tree, which was so thick that it would never havebeen penetrated by common English rain; but here, in acouple of minutes, a little torrent flowed down the trunk.It is to this violence of the rain that we must attribute theverdure at the bottom of the thickest woods: if the showerswere like those of a colder climate, the greater part wouldbe absorbed or evaporated before it reached the ground. Iwill not at present attempt to describe the gaudy sceneryof this noble bay, because, in our homeward voyage, wecalled here a second time, and I shall then have occasion toremark on it.

Along the whole coast of Brazil, for a length of at least2000 miles, and certainly for a considerable space inland,wherever solid rock occurs, it belongs to a granitic formation.The circumstance of this enormous area being constituted ofmaterials which most geologists believe to havebeen crystallized when heated under pressure, gives rise tomany curious reflections. Was this effect produced beneaththe depths of a profound ocean? or did a covering of strataformerly extend over it, which has since been removed?Can we believe that any power, acting for a time short ofinfinity, could have denuded the granite over so many thousandsquare leagues?

On a point not far from the city, where a rivulet enteredthe sea, I observed a fact connected with a subject discussedby

One day I was amused by watching the habits of theDiodon antennatus, which was caught swimming near theshore. This fish, with its flabby skin, is well known to possessthe singular power of distending itself into a nearlyspherical form. After having been taken out of water fora short time, and then again immersed in it, a considerablequantity both of water and air is absorbed by the mouth,and perhaps likewise by the branchial orifices. This processis effected by two methods: the air is swallowed, and is thenforced into the cavity of the body, its return being preventedby a muscular contraction which is externally visible: butthe water enters in a gentle stream through the mouth,which is kept wide open and motionless; this latter actionmust, therefore, depend on suction. The skin about theabdomen is much looser than that on the back; hence, duringthe inflation, the lower surface becomes far more distendedthan the upper; and the fish, in consequence, floatswith its back downwards. Cuvier doubts whether the Diodonin this position is able to swim; but not only can it thusmove forward in a straight line, but it can turn round toeither side. This latter movement is effected solely by theaid of the pectoral fins; the tail being collapsed, and notused. From the body being buoyed up with so much air, thebranchial openings are out of water, but a stream drawn inby the mouth constantly flows through them.

The fish, having remained in this distended state for ashort time, generally expelled the air and water withconsiderable force from the branchial apertures and mouth. Itcould emit, at will, a certain portion of the water, and itappears, therefore, probable that this fluid is taken in partlyfor the sake of regulating its specific gravity. This Diodonpossessed several means of defence. It could give a severebite, and could eject water from its mouth to some distance,at the same time making a curious noise by the movementof its jaws. By the inflation of its body, the papillae, withwhich the skin is covered, become erect and pointed. Butthe most curious circumstance is, that it secretes from theskin of its belly, when handled, a most beautiful carmine-redfibrous matter, which stains ivory and paper in so permanenta manner that the tint is retained with all its brightnessto the present day: I am quite ignorant of the natureand use of this secretion. I have heard from Dr. Allan ofForres, that he has frequently found a Diodon, floating aliveand distended, in the stomach of the shark, and that onseveral occasions he has known it eat its way, not onlythrough the coats of the stomach, but through the sides ofthe monster, which has thus been killed. Who would everhave imagined that a little soft fish could have destroyedthe great and savage shark?

March 18th. -- We sailed from Bahia. A few days afterwards,when not far distant from the Abrolhos Islets, my;attention was called to a reddish-brown appearance in thesea. The whole surface of the water, as it appeared under aweak lens, seemed as if covered by chopped bits of hay, withtheir ends jagged. These are minute cylindrical confervae,in bundles or rafts of from twenty to sixty in each. Mr. Berkeleyinforms me that they are the same species (Trichodesmium erythraeum)with that found over large spaces in the Red Sea, and whence its

Near Keeling Atoll, in the Indian Ocean, I observedmany little masses of confervae a few inches square, consistingof long cylindrical threads of excessive thinness, so asto be barely visible to the naked eye, mingled with otherrather larger bodies, finely conical at both ends. Two ofthese are shown in the woodcut united together. They varyin length from .04 to .06, and even to .08 of an inch inlength; and in diameter from .006 to .008 of an inch. Nearone extremity of the cylindrical part, a green septum, formedof granular matter, and thickest in the middle, may generallybe seen. This, I believe, is the bottom of a most delicate,colourless sac, composed of a pulpy substance, which linesthe exterior case, but does not extend within the extremeconical points. In some specimens, small but perfect spheresof brownish granular matter supplied theplaces of the septa; and I observed the curious process bywhich they were produced. The pulpy matter of the internalcoating suddenly grouped itself into lines, some of whichassumed a form radiating from a common centre; it thencontinued, with an irregular and rapid movement, to contractitself, so that in the course of a second the whole wasunited into a perfect little sphere, which occupied theposition of the septum at one end of the now quite hollow case.The formation of the granular sphere was hastened by anyaccidental injury. I may add, that frequently a pair of thesebodies were attached to each other, as represented above,cone beside cone, at that end where the septum occurs.

I will add here a few other observations connected withthe discoloration of the sea from organic causes. On thecoast of Chile, a few leagues north of Concepcion, the Beagleone day passed through great bands of muddy water, exactlylike that of a swollen river; and again, a degree south ofValparaiso, when fifty miles from the land, the same appearancewas still more extensive. Some of the water placedin a glass was of a pale reddish tint; and, examined undera microscope, was seen to swarm with minute animalculadarting about, and often exploding. Their shape is oval,and contracted in the middle by a ring of vibrating curvedciliae. It was, however, very difficult to examine them withcare, for almost the instant motion ceased, even while crossingthe field of vision, their bodies burst. Sometimes bothends burst at once, sometimes only one, and a quantity ofcoarse, brownish, granular matter was ejected. The animalan instant before bursting expanded to half again its naturalsize; and the explosion took place about fifteen secondsafter the rapid progressive motion had ceased: in a fewcases it was preceded for a short interval by a rotatorymovement on the longer axis. About two minutes after anynumber were isolated in a drop of water, they thus perished.The animals move with the narrow apex forwards, by theaid of their vibratory ciliae, and generally by rapid starts.They are exceedingly minute, and quite invisible to thenaked eye, only covering a space equal to the square of thethousandth of an inch. Their numbers were infinite; forthe smallest drop of water which I could remove containedvery many. In one day we passed through two spaces ofwater thus stained, one of which alone must have extendedover several square miles. What incalculable numbers ofthese microscopical animals! The colour of the water, asseen at some distance, was like that of a river which hasflowed through a red clay district, but under the shade ofthe vessel's side it was quite as dark as chocolate. The linewhere the red and blue water joined was distinctly defined.The weather for some days previously had been calm, and theocean abounded, to an unusual degree, with

In the sea around Tierra del Fuego, and at no great distancefrom the land, I have seen narrow lines of water of abright red colour, from the number of crustacea, whichsomewhat resemble in form large prawns. The sealers callthem whale-food. Whether whales feed on them I do notknow; but terns, cormorants, and immense herds of greatunwieldy seals derive, on some parts of the coast, theirchief sustenance from these swimming crabs. Seameninvariably attribute the discoloration of the water to spawn;but I found this to be the case only on one occasion. Atthe distance of several leagues from the Archipelago of theGalapagos, the ship sailed through three strips of a darkyellowish, or mudlike water; these strips were some mileslong, but only a few yards wide, and they were separatedfrom the surrounding water by a sinuous yet distinct margin.The colour was caused by little gelatinous balls, aboutthe fifth of an inch in diameter, in which numerous minutespherical ovules were imbedded: they were of two distinctkinds, one being of a reddish colour and of a different shapefrom the other. I cannot form a conjecture as to what twokinds of animals these belonged. Captain Colnett remarks,that this appearance is very common among the GalapagosIslands, and that the directions of the bands indicate thatof the currents; in the described case, however, the line wascaused by the wind. The only other appearance which Ihave to notice, is a thin oily coat on the water which displaysiridescent colours. I saw a considerable tract of theocean thus covered on the coast of Brazil; the seamenattributed it to the putrefying carcase of some whale, whichprobably was floating at no great distance. I do not heremention the minute gelatinous particles, hereafter to bereferred to, which are frequently dispersed throughout thewater, for they are not sufficiently abundant to create anychange of colour.

There are two circumstances in the above accounts whichappear remarkable: first, how do the various bodies whichform the bands with defined edges keep together? In thecase of the prawn-like crabs, their movements were ascoinstantaneous as in a regiment of soldiers; but this cannothappen from anything like voluntary action with the ovules,or the confervae, nor is it probable among the infusoria.Secondly, what causes the length and narrowness of thebands? The appearance so much resembles that which maybe seen in every torrent, where the stream uncoils into longstreaks the froth collected in the eddies, that I must attributethe effect to a similar action either of the currents of theair or sea. Under this supposition we must believe that thevarious organized bodies are produced in certain favourableplaces, and are thence removed by the set of either windor water. I confess, however, there is a very great difficultyin imagining any one spot to be the birthplace of the millionsof millions of animalcula and confervae: for whence comethe germs at such points? -- the parent bodies having beendistributed by the winds and waves over the immense ocean.But on no other hypothesis can I understand their lineargrouping. I may add that Scoresby remarks that greenwater abounding with pelagic animals is invariably foundin a certain part of the Arctic Sea.

Notes: