LYELL'S PRINCIPLES OF GEOLOGY.

Tins is the history of Nature in its widest sense. Just as the phi- losophical antiquary collects the dubious evidences of the history of a society during its dark and uncertain periods, so does the philosophical geologist, by an examination of the earth, of the • creatures that dwell upon its surface, and the remains of all those that have left traces of having lived there, make out a general idea of the revolutions of the globe. The earth is an old reformer ; her constitution has been subjected to innumerable changes ; the signs - of radical movements are to be detected everywhere . yet it is by no means easy to ascertain either the course or the causes of the revolutionary phenomena that so perpetually meet the eye of the inquirer. There are other investigations which more nearly affect our social happiness than the philosophy of geology, but perhaps there is none which in an indirect manner produce a more wholesome and beneficial effect upon the mind. Could the fly that confounded its own rotatory motion with the speed of the wheel, in which it had no concern save that of partaking of it, have been made to comprehend the precise character of a coach and four horses, with its various tracery and machinery, and the different uses which it served, and the character of the coachman who drove it, and the duties of his sta- tiont—the fly would assuredly have been a wiser, though not, perhaps, a better lly ; contemplation and intellectual enjoyment being no part of its nature, Of ours, they are. After the perusal of Mr. LYE L L'S volume, we confess to emotions of humility, to aspirations of the mind, to an elevation of thought, altogether foreign from the ordi- nary temper of worldly and busy men. Such a state of being is in itself of a superior order; but independent of this recommenda- tion, there is a direct tendency of a moral character. So disposed mentally, the heart overflows with charity and compassion' vanity shrivels into nothingness ; wrongs are forgotten, errors forgiven, prejudices fade away; the present is taken at its real value ; virtue is tried by an eternal standard. There are sermons in stones and tongues in brooks, but they want an interpreter: that interpreter is the enlightened geologist. Such a man is Mr. LYELL.

His book is not a theoretical one, though theories are its sub- ject; neither is it a practical one in the ordinary sense. It is a book of principles, quietly and patiently elicited from a most extra- ordinary number of facts. It may be said to be the general con- clusions which are to be drawn by an intelligent inquirer, who has placed before him the results of observation since geology began to be cultivated.

The first volume related to the changes which the inorganic world has undergone ; the subject of the second is the changes of the organic world now in progress. It is, in fact, the history of Vitality, as far as it can be traced from a consideration of the ani- mated creation.

Previous to entering upon a discussion of the evidences afforded by animated beings, whether existent or only appearing in their remains, it is necessary to settle the very curious question concern- ing the transmutation of species. For if according to an opinion prevalent generally, and lately ingeniously elaborated by some French naturalists, species in the progress of time change their character, and become as diversified as the circumstances in which they find themselves,—as, for instance, if the wolf, when domes • ticated, is the parent of the dog, and the ourang-outang is the original man,—then all reasoning from animal remains is at an end : it is impossible to proceed' from the present to the past. This theory has lately been expounded and defended with great ingenuity by LAMARCK; . who shows, after the most approved modern fashion, how an ourang-outang may be most philosophi- cally metamorphosed into a man. His opinions are reported with great care by Mr. LYELL ; and are examined, and, we think, if not successfully refuted, are at least shown not to be tenable on the grounds advanced by the French naturalist. The answer of Mr. LYE L L is a detailed examination of all we know respecting such changes as have been undergone by animals and plants within the limits of human experience. It is found, that in no instance is the departure wide under the influence of new circumstances, and the relapse into the original on the withdrawing of these circum- stances is universal. The changes, moreover, are always within certain limits, at which they stop, and are never carried further. An elephant, for instance, is capable of tuition up to a certain point : when it is reached, if he live a hundred years after, he never advances. The inquiry is carried into the consideration of the non-production of hybrids in animals and plants • in the course of which many curious facts are elicited on both sides. One fact, which would seem to favour the transmutation of species, and which has been lately observed, we cannot omit : it is as fol- lows, with Mr. LYELL'S commentary on it- Linnmus was of opinion that the primrose, oxlip, cowslip, and polyanthus, were only varieties of the same species. The majority of modern botanists, on the contrary, consider them to be distinct, although some conceived that the oxlip might be a cross between the cowslip and the primrose. Mr. Herbert has lately recorded the-follosiing experiment" I raised-froth the natural seed of one umbel of a highly-manured red cowslip; a primrose, a cowslip, oxlips of the usual and other colours, a black polyanthus, a hose-in-hose cowslip, and a na- tural paintrose bearing its flower on a polyanthus stalk. From the seed of that very hose-in-hose cowslip I have since raised a hose-in-hose primrose. I there- fore consider all these to be only local varieties depending upon soil and situation." Professor Ilminslent, of Cambridge, has since 'confirmed this experiment of Air. Herbert ; so that we have an examples not only of the remarkable varieties which the florist can obtain from a common stock, but of the distiactuess of analogous races found in a wild state. On what particular ingredient or quality in the earth these -changes depend, has not yet been ascertained. • But gardeners are well aware that particular plants, when placed under the influence of certain circumstances, are changed in various ways according to the species; and as often as the experiments are repeated, si- milar results are obtained. - The nature of these results, however, depends neon the species, and they are, therefore, part of the specific character ; they exhibit the same phenomena again and again, and indicate certain fixed and invariable relations between the physiological peculiarities of the plant, and the influence of certain external agents. They afford no ground for questioning the instability of species, but rather the contrary ; they present us with a class of phenomena winch, when they are more thoroughly understood, may afford some of the best tests for identifying species, and posing that the attributes originally conferred endure so long as any issue of the original stock remains upon the earth.

After settling the question of the eternal distinction between the existing species, the author proceeds to their various characteris- tics, and the great events of their. history,—such as the laws which regulate their geographical distribution, the circumstances of migration, or change of station and habitation, and more parti- • cularly, the -theory of their successive exthiction. He then proceeds to the effects produced by the powers of vitality on the state of the earth's surface; and thus gradually passes in review all the phenomena which in the course of ages appear to be indebted for their existence to the presence of animated agents. The detail is luminous; the spirit in which the phenomena are examined is sage and Cautious; - the results enthiavourecl to be established we believe to be rational and welt-founded. It Would scarcely be proper, within our limits; to enter into any analysis of his views: we prefer to make a selection from the leading circumstances which he employs iddrawing his more important conclusions : they are of the nature tiffiletS, and are more likely to interest curiosity and attract in- quiry than a more general and abstract report.

TRANSMISSION OF SEEDS BY WATER. •

In turning our attention, in the next place, to the instrumentality of the aqueous agents of dispersion, we cannot do better than cite the words of one of our ablest botanical writers. " The Mountain stream or torrent," observes Keith, " washes down to the valley the seeds which may accidentally fall into it, or which it May happen to sweep from its baliks when it suddenly overflows them. . The broad and majestic river, winding along the extensive plain, and traversing the continents of the world, conveys to the distance of many hun- dreds of miles the seeds that may have vegetated at its source. Thus the south- ern Shines Of the Wait are visited bYseeds which grew in the interior of Ger- many ;, and the-syestern shores of the Atlantic by seeds that hive been generated in the Interim' of-America." 'Fruits, moreover, indigenous to America and the West Indiesssuch as that of the • Mimosa scandens, the cashew-nut, and others, hare been known to be drifted across the Atlantic by the Gulf-stream, on the western coasts of Europe, in such a state that they might have vegetated had the climate and soil been favourable. Among these, the'Guilantlina Bondue, a leguminous 'plant, is particularly mentioned, as having. been raised from a seed found on the west coast of Ireland. Sir Hans Sloane informs us that the lenti- cola marina, or sargasso—a bean which is frequently cast ashore on the Orkney Isles, and coast of Ireland—grows on the rocks about Jamaica, where the surface of the sea is sometimes strewed with it, and from whence it is known to be car- ried by the winds and currents towards the coast of Florida.

TRANSMISSION OF • SEEDS. BY BIRDS. Pulpy fruits serve quadrupeds and birds as.food ; while their seeds, often hard and indigestible, pass uninjured through the intestines, awl . are deposited tar from their original place of growth in a condition peculiarly fit for vegetation. SO well are our farmers, in some parts of England, aware of this fact, that when they desire* to raise a quick-set hedge in the shortest possible time, they feed turkeys with the haws of the common_white-thorn ( Crattegus oxyaeantha), and then sow the stones which are ejected in their excrement, whereby they gaidadentire year in the growth of the plant. Birds, when they pluck cher- ries, sloes, and haws, fly away with them to some convenient place, and when they have devoured the fruit drop the stone into the ground. Captain Cook, in his account of the volcanic island of Tanna, one of the New Hebrides, which he visited in his second voyage, ntakes the following interesting observation— "Mr. Forster, in his botanical excursion this day, shot a pigeon, in the craw of which was a wild nutmeg:. He took some pains to find the.tree on this is- land, but his endeavours were without success." It is easy, therefore, to per- ceive, that birds in their Migrations to great distances, and even across seas, may transport seeds to new isles and continents.

THE OCCASIONALITY OF PLAGUES OF INSECTS.

If for the sake of employing, on different but rare occasions, a power of many hundred horses, we were under the necessity of feeding all these animals at great cost in the intervals when their services were not required, we should greatly admire the invention of a machine, such as the steam-engine, which was capable, at any moment, of exerting the same degree Of strength without any consumption of food during periods of inaction. The same kind of admira- tion is strongly excited when we contemplate the powers of insect life, in the creation of which Nature has been so prodigal. A scanty nuMber of minute individuals, only to be detected by careful research, are ready in a few days, weeks, or months, to give birth to myriads which may repress any degree of monopoly. in another species, or remove nuisances, such as dead carcasses, which might taint the air ; but no sooner has the destroying commission been executed, than the gigantic power becomes dormant—each of the mighty h-ost soon reaches the term of its transient existenee, and the season arrives when the whole species passes naturally into the egg, and thence into the larva and pupa state. In this defenceless condition it may be destroyed, either by the elements, or.by the augmentation of some of its numerous foes, which may prey upon it in these stages of its transformation ; or it'ofMn 'happens that, in the following year, the season proves unfavourable to the hatching of the eggs or,the develop-

ment of the pence.- • •

'Thus the swarming myriads depart whichsmayhave 'covered the vegetation like the aphides, or darkened the air like locusts. In almost every season there are some species which in this manner put forth their strength, and then, like Illilton's spirits which thronged the spacious hall, "reduce to smallest forms their shapes immense So Oda. the.aerY eiowd . 'Swarra'd and were straiten'd; tilj. the'signal given,

Behold a wonder ! they.but now who seem'd . In bigness to surpass earth's giant sons. Now less than smallest dwarfs. . . •

A few examples will illustrate the mode in which this force operates. It is well known that among the countless species of the insect creation, some feed on animal, others on vegetable matter ; and, upon considering a catalogue of eight thousand British insects and arachnidas, Mr. Kirby found that these two divisions were nearly a counterpoise to each other, the carnivorous being somewhat preponderant. . There am also distinct species,—some appointed to consume living, others dead or putrid animal and vegetable substances. One female of Masco earnaria • will give birthlo' twenty thousand young ; and the laryn of .many flesh-flies devour so much food in twenty-four hours, and grow Si) quickly, as to increase their weight two hundredfold ! In five days after being hatched they arrive at their full-growth and size, so that there was ground, says Kirby, for the assertion of Linureus, that three flies of M. vomitoria could devour a dead horse as quickly as a lion ; and another Swedish naturalist re- marks, that so great are the powers of propagation of a single species, even of the smallest insects, that each can commit, when required, more ravages than the elephant.

. MARINE POPULATION.

The ocean teems with life—the class of polyps alone are conjectured by Lamarck to be as strong in individuals as insects. Every tropical reef is de- scribed as bristling with corals; -budding with sponges, and swanning with crustacea, echini, and testacea ; while alinwt every tide-washed rock is carpeted with fuci and studded with corallines, actiniie, and mollusca. _There are Innu- merable forms in the seas of the warmer zones, which have scarcely begun to attract the attention of the naturalist ; and there are parasitic animals without number, three or four of which are sometimes appropriated to one genus, as to the Bahrna, for example. Even though we concede, therefore, tint the geo- graphical range of marine species is more extensive in general than that of time terrestrial (the temperatare of time sea being more uniform, and the land im- peding less the migrations of the oceanic than the ocean those of the terres- trial), yet we think it most probable that the aquatic species far exceed in num- ber the inhabitants of the land.

Without insisting on this point,. we may safely assume, as we before stated, that, exclusive of microscopic baings, there are between one and two millions of species now inhabiting the terraqueous globe; so that if only one of these were-to become extinct annually, and one new one were to be every year called into being, more than a million of years would be required to bring about a complete revolution in organic life.

• AGENCY OF MAN IN EXTINGUISHING OR SPREADING SPECIES.

Let us make some inquiries into the extent of the influence which the pro- gress of society has exerted, during the last seven or eight _centuries, in alter- ing the distribution of our indigenous British animals. Dr. Fleming has pro- secuted this inquiry with his usual zeal and ability, and in a memoir on the sub- ject has enumerated the best-authenticated examples of the decrease or extirpa- tion of certain species during a period when our population has made the most rapid- advances. We shall offer a brief outline of ins results. - Che stag, as Well as the fallow-deer and the roe, were formerly so abundant that, according to Lesley,- from five hundred to a thousand were sometimes slain at a hunting-match ; but thenative races would already have been extinguished, had they not been carefully preserved in certain forests. The otter, the marten, and time e polecat, were also n sufficient numbers to be pursued for the sake of their fur ; but they have now been reduced within very narrow hounds. - The wild cat and fox have alsolieen sacrificed throughout the greater part of the country' for the security of the poultry-yard or the fold, . Badgers have been expelled from nearly every district which at formes periods they inhabited. Besides these, which have been driven out from some haunts, and everywhere reduced in number, there are Some which have been wholly, extirpated ; such as the ancient breed- of indigenous horses, the wild boar and the wild oxen, of which last, however, it few remains are still preserved in the parks of some of our nobility. The beaver, which was eagerly sought after for its fur, had became scaree at the close Of the ninth century, and, by the twelfth century, was only to be met with, according to Giraldus de Barn, in one river in Wales, and another in Scothunl. The wolf, once so much dreaded by our ancestors, is said to have maintained its ground in Ireland so late as the beginning of the eighteenth' cent* (1710), though it had been extirpated in Scotland thirty years before, and in England at a much earlier period. The bear, which in Wales was regarded as a beast of the chace equal to the hare or the boar, only

perished as a native of Scotland in the year 1057. .

Many native birds of prey have also been the subjects of unremitting perse- cution. The eagles, larger' hawks, and ravens, have disappeared from the more cultivated districts. The haunts of the mallard, the snipe, the redshank, and the bittern, have been drained equally with the summer dwellings of the lap- wing and the curlew. But these species still linger in some portion of the Brt- tish isles ; whereas the large capercailzies, or wood grouse, formerly natives of the pine-forests of Ireland and Scotland, have been destroyed Within the last fifty years. The egret and the crime, which appear to have been formerly very com- mon in Scotland, are now only occasional visitants. . The limatard (Otis tardrt), observes Graves in his British Ornithology, "was formerly seen in the downs and heaths of various parts of our island, in flocks of forty or fifty birds ; whereas it is now a circumstance of rare occur- rence to meet with a single individual." Bewick also remarks, "that they were formerly more common in this island than at present ; they are now found onlyin the open counties of the south and east, in the plains of...Wiltshire Dor- setshire and some parts of Yorkshire." In the few years that have elapsed since liewick wrote, this bird has entirely disappeared from Wiltshire and Dorsetshi: e.

These changes, we may observe, are derived from very imperfect memorials, and relate only to the larger and more conspicuous animals inhabiting .a small spin on the globe but they cannot fail to exalt our conception of the enormous revolutions which, in the course of several thousand years, the whole humeri species must have effected. The kangaroo and the emu are retreating rapidly before the progress of colo- nization in Australia ; and it scarcely admits of doubt, that the general cultiva- tion of that country must lead to the extirpation of both. The most striking example of the loss, even within the last two centuries, of a remarkable species, is that Of the dodo—a bird first seen by the Dutch when they landed on the Isle of France, at that time uninhabited, immediately after the discovery of the pas- sage to the East Indies by the Cape of Good Hope. It was of a large size and singular form ; its wings short, like those of an ostrich, and wholly incapable of sustaining its heavy body even for a short flight. In ita general appearance it

differed from the ostrich, cassowary,.or any known bird. •

Many naturalists gave- figures of the dodo after the .commencement of the seventeenth century; and there is a painting of it in the British Museum, which • is aid to have been taken from a living individual. • Beneath the painting is leg, in a fine state of preservation, which ornithologists are agreed cannot be- long to any other known bird. In the museum at Oxford, also, there is a foot and a head, in an imperfect state, but M. Cuvier doubts the identity of this species with that of which the painting is preserved in London.

In spite of the most active search, during the last century, no information re- specting the dodo was obtained, and some authors have.gone so far as to pretend

that it never existed ; but amongst a great mass of satisfactory evidence in favour of the recent existence of this species, we may mention that an assemblage of fossil bones were recently discovered' under a bed of lava, in the Isle of France, and sent to the Paris museum by M. Desjardins. They almost all belonged to a large living species of land-tortoise, called Testudo Indica, but amongst them were the head, sternum, and humerus of the (halo. M. Cuvier showed me these valuable remains in Paris, and assured me that they left no doubt in his mind that the huge bird was one of the gallinaceous tribe. Next to. the direct agency of man, his indirect influence in multiplying the numbers of large herbivorous quadrupeds of domesticated races may be re- garded as one of. the most obvious causes of the extermivation ("species. On this, and on several other grounds, the introduction of the horse, ox, and other inammalia, into America, and their rapid propagation over that continent within the last three centuries, is a fact of great importance in natural history. The e.xtraordiniry herds of wild cattle and horses which overran the plains of South America, sprung from a very few pairs first carried over by the Spaniards ; and they prove that the wide geographical range of large species in great continents does not necessarily imply that they have existed there from remote periods. Humboldt observes, in his Travsls, on the authority of Azzara, that it is believed there exist, in the Pampas of Buenos Ayres, twelve million cows and three mil- lion horses, without comprising in this enumeration the cattle that have no ac- .knowledged Proprietor. In the Llanos of. Caraccas, the rich hateros, or pro- prietor of pastoral farms, are entirely ignorant of the number of cattle they pos- sess. The young are branded with a mark peculiar to each herd, and some of the most wealthy owners mark as many as fourteen thousand a year. In the northern plains, from the Orinoco to the lake of Maracaybo' M. Depons reckoned that one million two hundred thousand oxen one hundred and eighty thousand horses, and ninety thousand mules, wandered at large. In some parts of the valley of the Mississippi, especially in the country of the Osage Indians, wild horses are immensely numerous'. The establishment of black cattle in America dates from Columbus's second voyage to St. Domingo: They there multiplied rapidly ; and that island.pre- sently became a kind of nursery from which these animals were successively transported to various parts of the continental coast, and from thence into the interior. Nothwithstandiog these ninnerous exportations, in twenty-seven years after the discovery of the island, herds of four thousand head, as we learn from Oviedo, were not uncommon, and there were even some that amounted to eight thousand. In 1587, the number of hides exported from St. Domingo alone, according to Acosta'S report, was thirty-five thousand four hundred and forty-four; and in the same year there were exported sixty-four thousand three hundred and fifty from the ports of New Spain. This was in the sixty-fifth year after the taking of Mexico, -previous to which event the Spaniards, who came into that country, had not been able to engage in any thing else than war. All our readers are aware that these animals are now established throughout the American continent, from Canada to Paraguay. The ass has thriven very generally in the New World and we learn from Tflloa, that in Quito they ran wild, and multiplied in amazing numbers, so as to become a nuisance. They grazed together in herds, and, when attacked, de- fended themselves with their mouths. If a horse happened to stray into the places where they fed, they all fell upon him, and did not cease biting and kick- mg till they left him dead.

The first hogs were carried to America by Columbus, and established in the island of St. Domingo the year following its discovery in November 1493. In succeeding years they were introduced into other places where the Spaniards settled ; and, in the space of half a century, they were found established in the New World, from the latitude of 25° north, to the 40th degree of south latitude. Sheep, also, and ,coats Wave multiplied enormously in the New World, as have also the cat and the rat, which last, as we before stated, has been imported un- intentionally in ships. The dogs introduced by man, which have at different periods become wild in America, hunted in packs like the wolf and the jackal, destroying not only hogs, but the calves and foals of the wild cattle and horses.

!Aloe in his voyage, and Buffon on the authority of old writers, relate a fact which illustrates very clearly the principle before explained by us, of the check which the increase of one animal necessarily offers te that of another. The Spaniards had introduced goats into the island of Juan Fernandez, where they became so prolific as to furnish the pirates who infested those seas with pro- visions. In order to cut off this resource from the buccaneers, a number of dogs were turned loose into the island; and so numerous did they become in their turn, that they destroyed the goats in every accessible part, after which the number of the wild dogs again decreased.

As an example of the rapidity with which a large tract may become peopled by the offspring of a single pair of quadrupeds, we may mention that in the year 1773 thirteen rein-deer were exported from Norway, only three of which reached Iceland. These were turned loose into the mountains Of Guldbringe Syssel, where they multiplied so greatly, in the course of forty years, that it was not uncommon to meet with herds consisting of from forty to one hundred in various districts.