Blackwood's Edinburgh Magazine, Volume 66, No. 408, January 1849

Within the memory of a living man, there has been such progress and revolution in science, that not one of the great generalisations taught him in his youth can be now received as uncontested propositions. Not many years ago, how commodiously a few words, such as attraction, caloric, affinity, rays of light, and others, could be used, and how much they seemed to explain! Caloric was a fluid, unseen indeed, but very obedient to the imagination – expanding bodies, and radiating from one to the other in a quite orderly manner. What is it now? Perhaps the vibration of a subtle ether interfused through all bodies; perhaps the vibration of the atomic parts themselves of those bodies. Who will venture to say? Attraction and affinity are no longer the clearly defined ultimate facts they seemed to be; we know so much, at least, that they are intimately connected with electrical phenomena, though not to what extent. That electricity is implicated with chemical composition, and recomposition, is clearly recognised; and Sir J. Herschel has lately expressed his opinion, that it is impossible any longer to attempt the explanation of the movements of all the heavenly bodies by simple attraction, as understood in the Newtonian theory – these comets, with their trains perversely turned from the sun, deranging sadly our systematic views. The ray of light, which, with its reflection and its refraction, seemed a quite manageable substance, has deserted us, and we have an ethereal fluid – the same as that which constitutes heat, or another – substituted in its stead. Science has no language, and knows not how to speak. If she lectures one day upon the "polarisation" of light, she professes the next not to know what she means by the term; she is driven even to talk of "invisible rays" of light, or chemical rays. Never was it so difficult to form any scientific conception on these subjects, or to speak of them with any consistency. Mrs Somerville is a correct writer; yet she opens her brief section upon magnetism thus: – "Magnetism is one of those unseen imponderable existences, which, like electricity and heat, are known only by their effects. It is certainly identical with electricity, for," &c. It is like, and it is identical, in almost the same sentence.

Even in the fields of astronomy, where we have to deal with large masses of matter, it is no longer possible for the imagination to form any embraceable system. We are plunged into hopeless infinitude, and the little regularities we had painfully delineated on the heavens are all effaced. The earth had been torn from its moorings and sent revolving through space, but it revolved round a central stationary sun. Here, at least, was something stable. The sun was a fixed centre for our minds, as well as for the planetary system. But the sun himself has been uprooted, and revolves round some other centre – we know not what – or else travels on through infinite space – we know not whither. A little time ago, the stately seven rolled round their central orb in clear and uninterrupted space; their number has been constantly increasing; we reckon now seventeen planetary bodies that can be reduced to no law of proportion or harmony, either as to their size, their orbits, the inclination of their axes, or any other planetary property;[15 - "Nor are there," writes Humboldt, "any constant relations between the distances of the planets from the central body round which they revolve, and their absolute magnitudes, densities, times of rotation, eccentricities and inclinations of orbit and of axis. We find Mars, though more distant from the sun than either the earth or Venus, inferior to them in magnitude; Saturn is less than Jupiter, and yet much larger than Uranus. The zone of the telescopic planets, which are so inconsiderable in point of volume, viewed in the series of distances commencing from the sun, comes next before Jupiter, the greatest in size of all the planetary bodies. Remarkable as is the small density of all the colossal planets which are farthest from the sun, yet neither in this respect can we recognise any regular succession. Uranus appears to be denser than Saturn, and (though the inner group of planets differ but little from each other in this particular) we find both Venus and Mars less dense than the earth, which is situated between them. The time of rotation increases, on the whole, with increasing solar distance, but yet it is greater in Mars than in the earth, and in Saturn than in Jupiter." After other remarks of the same character, he adds, "The planetary system, in its relation of absolute magnitude, relative position of the axis, density, time of rotation, and different degrees of eccentricity of the orbits, has, to our apprehension, nothing more of natural necessity than the relative distribution of land and water on the surface of our globe, the configuration of continents, or the elevation of mountain chains. No general law, in these respects, is discoverable either in the regions of space or in the irregularities of the crust of the earth."] and the space they circulate in is intruded on by other smaller and miscellaneous bodies, asteroids, and the like, some of which, it seems, occasionally fall to the earth. Comets come sweeping in from illimitable space, requiring, it is thought, some eight thousand years for their revolution round the sun. Some of these cross each other's orbits: one has crossed the orbit of the earth; and their decreasing circle round the sun, gives notice of some unknown ether suffused through the interstellar spaces. The outlying prospect, beyond our system, grows still more bewildering. The stars are no longer "fixed," nor is their brilliancy secured to them; this increases and diminishes with perplexing mystery. What seemed a single point of light, resolves itself into two stars revolving round each, perhaps reciprocally sun and planet. The faint and telescopic nebula, just reached by the glass in one age, is found in the next to be a congregation of innumerable stars. Our milky way is, at the same distance, just such another nebula. "The elder Herschel calculates that the light of the most distant nebula, discovered by his forty-feet refractor, requires two millions of years to reach our eyes." Oh, shut up the telescope! the reason reels.

Science, in short, presents before us a field of perpetual activity – of endless excitement, and that of the highest order – of practical results of the greatest utility and most beneficial description; but it gives no prospect of any resting-place – any repose for the speculative reason – any position with which the scientific mind shall be content, and from which it shall embrace the scene before it in its unity and harmony. Always will it be

"Moving about in worlds half-realised."

Having touched upon these subtle agencies of light, and heat, and electricity, and on the increasing difficulty we have of framing to ourselves any distinct conception of them, we cannot refrain from alluding to a little work or pamphlet, by Mr Grove, entitled, The Correlation of Physical Forces, in which this subject is treated with great originality. Mr Grove has made himself a name in experimental science by his discoveries in electricity and chemistry; in this pamphlet he shows, that he has the taste and power for enlarged speculation on the truths which experiment brings to light. We would recommend the perusal of his pamphlet to all who are interested in these higher and more abstract speculations. How far the wide generalisation he adopts is sustained by facts, we are not prepared to say. But it is a powerful work, and it is a singular one; for it is not often, in this country at least, that a man so well versed in the minutiæ of science ventures upon so bold a style of generalisation. After reviewing some of the more lately discovered properties of electricity, heat, light, and magnetism, and showing how each of them is capable of producing or resolving itself into the others, he reasons that all the four are but the varied activity of one and the same element. He adds, that this element is probably no other than the primitive atom itself; and that, in fact, these may be all regarded as affections of matter, which follow in their legal sequence, and not as the results of separate fluids or ethers. We are not sure that we do justice to his views, as we have not the work at hand, and it is some time since we read it; but we are persuaded that its perusal will be of interest to a philosophic reader, though its reasoning should fail to satisfy him.

But we have not placed the title of Mrs Somerville's book at the head of this paper, as an occasion to involve ourselves in these dark and abstract discussions. We are for out-of-door life; we would survey this visible round world, whose various regions, with their products and their inhabitants, she has brought before us.

"Physical geography," thus commences our writer, "is a description of the earth, the sea, and the air, with their inhabitants animal and vegetable, of the distribution of these organised beings, and the causes of that distribution. Political and arbitrary divisions are disregarded: the sea and the land are considered only with respect to these great features, that have been stamped upon them by the hand of the Almighty; and man himself is viewed but as a fellow-inhabitant of the globe with other created things, yet influencing them to a certain extent by his actions, and influenced in return."

Physical geography stands thus in contrast with political and historical geography. Russia is here no despotism, and America no democracy; they are only portions of the globe inhabited by certain races. To some persons it will doubtless seem a strange "geography" that takes no notice of the city, and respects not at all the boundaries of states. Those to whom the name recalls only the early labours of the school-room, when counties and county-towns formed a great branch of learning – where the blue and red lines upon the map were so anxiously traced, and where, doubtless, some suspicion arose that the earth itself was marked out by corresponding lines, or something equivalent to them – will hardly admit that to be geography which takes no note of these essential demarcations, or allow that to be a map in which the very city they live in cannot be found. To them the Physical Atlas will still seem nothing but a series of maps, in which most of the names have still to be inserted. They unconsciously regard cities and provinces as the primary objects and natural divisions of the earth. They share something of the feeling of that good man, more pious than reflective, who noted it as all especial providence that all the great rivers ran by the great towns.

Others, however, will be glad to escape for a time from these landmarks which man has put upon the earth, and to regard it in its great natural lineaments of continent and sea, mountain and island. To do this with advantage, it is necessary to disembarrass ourselves, both in the book and the map, of much that in our usual nomenclature ranks pre-eminently as geography. Nor is it easy to study this, more than the older branch of geography, without an appropriate atlas. To turn over the maps of Mr Johnston's, and con the varied information which accompanies them, is itself a study, and no disagreeable one. Of the extent of this information we can give no idea by extract or quotation; it is manifestly in too condensed a form for quotation; it is a perfect storehouse of knowledge, gathered from the best authorities.

The first thing which strikes an observant person, on looking over a map, or turning round a globe, is the unequal division and distribution of land and water. Over little more than one-fourth of the surface of the earth does dry land appear; the remaining three-fourths are overflowed by water. And this land is by no means equally disposed over the globe. Far the greater part of it lies in the northern hemisphere. "In the northern hemisphere it is three times greater than the south."

Of the form which this land assumes, the following peculiarities have been noticed: —

"The tendency of the land to assume a peninsular form is very remarkable, and it is still more so that almost all the peninsulas tend to the south – circumstances that depend on some unknown cause which seems to have acted very extensively. The continents of South America, Africa, and Greenland, are peninsulas on a gigantic scale, all tending to the south; the Asiatic peninsula of India, the Indo-Chinese peninsula, those of Corea, Kamtchatka, of Florida, California, and Aliaska, in North America, as well as the European peninsulas of Norway and Sweden, Spain and Portugal, Italy and Greece, take the same direction. All the latter have a rounded form except Italy, whereas most of the others terminate sharply, especially the continents of South America and Africa, India, and Greenland, which have the pointed form of wedges; while some are long and narrow, as California, Aliaska, and Malacca. Many of the peninsulas have an island, or group of islands, at their extremity – as South America, which terminates with the group of Terra del Fuego; India has Ceylon; Malacca has Sumatra and Banca; the southern extremity of New Holland ends in Van Diemen's Land; a chain of islands run from the end of the peninsula of Aliaska; Greenland has a group of islands at its extremity; and Sicily lies close to the termination of Italy. It has been observed, as another peculiarity in the structure of peninsulas, that they generally terminate boldly, in bluffs, promontories, or mountains, which are often the last portions of the continental chains. South America terminates in Cape Horn, a high promontory which is the visible termination of the Andes; Africa with the Cape of Good Hope; India with Cape Comorin, the last of the Ghauts; New Holland ends with South-East Cape in Van Diemen's Land; and Greenland's farthest point is the elevated bluff of Cape Farewell."

These are peculiarities interesting to notice, and which may hereafter explain, or be explained by, other phenomena. Resemblances and analogies of this kind, whilst they are permitted only to direct and stimulate inquiry, have their legitimate place in science. It was a resemblance of this description, between the zig-zag course of the metalliferous veins, and the path of the lightning, which first suggested the theory, based, of course, on very different reasonings, that electricity had essentially contributed to the formation of those veins – a theory which Mrs Somerville has considered sufficiently sound to introduce into her work.

What lies within our globe is still matter of conjecture. The radius of the earth is 4000 miles, and by one means or another, mining, and the examination of the upheaved strata, and of what volcanoes have thrown out, we are supposed to have penetrated, with speculative vision, to about the depth of ten miles.

"The increase of temperature," writes Mrs Somerville, "with the depth below the surface of the earth, and the tremendous desolation hurled over wide regions by numerous fire-breathing mountains, show that man is removed but a few miles from immense lakes or seas of liquid fire. The very shell on which he stands is unstable under his feet, not only from those temporary convulsions that seem to shake the globe to its centre, but from a slow, almost imperceptible, elevation in some places, and an equally gentle subsidence in others, as if the internal molten matter were subject to secular tides, now heaving and now ebbing; or that the subjacent rocks were in one place expanded and in another contracted by changes in temperature."

Perhaps these "immense lakes or seas of liquid fire" are a little too hastily set down here in our geography. But of these obscure regions beneath the earth, the student must understand he can share only in the best conjectures of scientific men. Geology is compelled, at present, in many cases, to content herself with intelligent conjecture.

To return again to the surface of the earth, the first grand spectacle that strikes us is the mountains. Before it was understood how the mountain was the parent of the river, the noble elevation was apt to be regarded in the light of a ruin, as evidence of some disastrous catastrophe, and Burnett, in his Theory of the Earth, conceived the ideal or normal state of our planet to be that of a smooth ball, smooth as an egg. The notion not only betrays the low state of scientific knowledge in his age, but a miserable taste in world-architecture, which, we may remark in excuse for poor Burnett, was, almost as much as his scientific ignorance, to be shared with the age in which he lived. For it is surprising, with the exception of a few poets, how destitute men were, in his time, of all sympathy with, and admiration of, the grander and more sublime objects of nature. "We have changed all that!" The mountain range, pouring down its streams into the valleys on both sides, is not only recognised as necessary to the fertility of the plain; but, strange to say, we become more and more awake to its surprising beauty and magnificence. The description of the mountain ranges of the several continents of the world, forms one of the principal attractions of the study of physical geography, and one of the great charms of Mrs Somerville's book.

The mountains of Asia take precedence of all others in altitude and length of range.

"The mean height of the Himalaya is stupendous. Captain Gerard and his brother estimated that it could not be less than from 16,000 to 20,000 feet; but, from the average elevation of the passes over these mountains, Baron Humboldt thinks it must be under 15,700 feet. Colonel Sabine estimates it to be only 11,510 feet, though the peaks exceeding that elevation are not to be numbered, especially at the sources of the Sutlej. Indeed, from that river to the Kalee, the chain exhibits an endless succession of the loftiest mountains on earth: forty of them surpass the height of Chimborazo, one of the highest of the Andes, and several reach the height of 25,000 feet at least… The valleys are crevices so deep and narrow, and the mountains that hang over them in menacing cliffs are so lofty, that these abysses are shrouded in perpetual gloom, except where the rays of a vertical sun penetrate their depths. From the steepness of the descent the rivers shoot down with the swiftness of an arrow, filling the caverns with foam and the air with mist.

"Most of the passes over the Himalaya are but little lower than the top of Mont Blanc; many are higher, especially near the Sutlej, where they are from 18,000 to 19,000 feet high; and that north-east of Khoonawur is 20,000 feet above the level of the sea, the highest that has been attempted. All are terrific, and the fatigue and suffering from the rarity of the air in the last 500 feet is not to be described. Animals are as much distressed as human beings, and many of them die; thousands of birds perish from the violence of the winds; the drifting snow is often fatal to travellers, and violent thunder-storms add to the horror of the journey. The Niti Pass, by which Mr Moorcroft ascended to the sacred lake of Manasa, in Tibet, is tremendous: he and his guide had not only to walk bare-footed, from the risk of slipping, but they were obliged to creep along the most frightful chasms, holding by twigs and tufts of grass, and sometimes they crossed deep and awful crevices on a branch of a tree, or on loose stones thrown across. Yet these are the thoroughfares for commerce in the Himalaya, never repaired, nor susceptible of improvement, from frequent landslips and torrents.

"The loftiest peaks, being bare of snow, give great variety of colour and beauty to the scenery, which in these passes is at all times magnificent. During the day, the stupendous size of the mountains, their interminable extent, the variety and sharpness of their forms, and, above all, the tender clearness of their distant outline melting into the pale blue sky, contrasted with the deep azure above, is described as a scene of wild and wonderful beauty. At midnight, when myriads of stars sparkle in the black sky, and the pure blue of the mountains looks deeper still below the pale white gleam of the earth and snow-light, the effect is of unparalleled sublimity; and no language can describe the splendour of the sunbeams at daybreak streaming between the high peaks, and throwing their gigantic shadows on the mountains below. There, far above the habitation of man, no living thing exists, no sound is heard; the very echo of the traveller's footsteps startles him in the awful solitude and silence that reigns in these august dwellings of everlasting snow."

The table-lands of Asia are on a scale corresponding with its mountains. But the same elevation, it is remarked, is not accompanied with the same sterility in these parts of the world, as in the temperate zone. Corn has been found growing at heights exceeding the summit of Mont Blanc. "According to Mr Moorcroft, the sacred lake of Manasa, in Great Tibet, and the surrounding country, is 17,000 feet above the sea, which is 1240 feet higher than Mont Blanc. In this elevated region wheat and barley grow, and many of the fruits of Southern Europe ripen. The city of H'Lassa, in eastern Tibet, the residence of the Grand Lama, is surrounded by vineyards, and is called by the Chinese 'the Realm of Pleasure!'" Nevertheless the general aspect of the table lands is that of a terrific sterility. Here is a striking description of them. We should have been tempted to say, that in this singularly dark appearance of the sky at mid-day, there was something of exaggeration, if our own limited experience had not taught us to be very cautious in attributing exaggeration where the scenic effects of nature are concerned.

"In summer the sun is powerful at mid-day; the air is of the purest transparency, and the azure of the sky so deep that it seems black as in the darkest night. The rising moon does not enlighten the atmosphere; no warning radiance announces her approach, till her limb touches the horizon, and the stars shine with the distinctness and brilliancy of suns. In southern Tibet the verdure is confined to favoured spots; the bleak mountains and high plains are sternly gloomy – a scene of barrenness not to be conceived. Solitude reigns in these dreary wastes, where there is not a tree, nor even a shrub to be seen of more than a few inches high. The scanty, short-lived verdure vanishes in October; the country then looks as if fire had passed over it; and cutting dry winds blow with irresistible fury, howling in the bare mountains, whirling the snow through the air, and freezing to death the unfortunate traveller benighted in their defiles."

The description of the territory of the East India Company will be read with interest. We cannot afford space to extract it. Plains and valleys the very richest in the globe are to be found here, as also much rank marshy land, and also much jungle. "It has been estimated that a third of the East India Company's territory is jungle."

As a set-off against this jungle we have it intimated that, if proper search were made, gold would probably be found in this territory, as abundantly as in California. We sincerely hope no such discovery will be made. If there is a sure specific for demoralising a people, it is to involve them in the chase for gold, instead of that profitable industry which produces the veritable wealth for which gold has become the symbol and representative. The discovery of gold in one of our colonies would not only demoralise, it would impoverish. It would demoralise, by substituting for steady industry, with steady returns, a species of enterprise which has all the uncertainty and fluctuation of gambling; and it would finally impoverish by diverting labour from the creation of agricultural and manufacturing wealth, to the obtaining of the dry barren symbol of wealth, which, apart from its representative character, has but very little value whatever.

We will not look back towards Chimborazo and the Andes, as we should involve ourselves in long and tempting descriptions. In Africa, it is remarkable that we are little acquainted with the mountains. "No European has yet seen the Mountains of the Moon!" What a challenge to enterprising travellers! We know the level sands of Africa better than these elevations which have assumed so magnificent a title. What a terrific sterility does a large portion of this the most ill-fated of the great continents present! "On the interminable sands and rocks of these deserts no animal – no insect – breaks the dread silence; not a tree nor a shrub is to be seen in this land without a shadow. In the glare of noon the air quivers with the heat reflected from the red sand, and in the night it is chilled under a clear sky sparkling with its host of stars." The wind of heaven, which elsewhere breathes so refreshingly, is here a burning blast fatal to life; or else it drives the sand in clouds before it, obscuring the sun, and stifling and burying the hapless caravan.

In the new continent of America – if it still retains that title – the desert is comparatively rare. But its enormous forests have, in some regions, proved that excessive vegetation can assume almost as terrific an appearance as this interminable sterility.

"The forests of the Amazons not only cover the basin of that river, from the Cordillera of Chiquitos to the mountains of Parima, but also its limiting mountain-chains, the Sierra Dos Vertentes and Parima, so that the whole forms an area of woodland more than six times the size of France, lying between the 18th parallel of south latitude and the 7th of north, consequently inter-tropical and traversed by the equator. According to Baron Humboldt, the soil, enriched for ages by the spoils of the forest, consists of the richest mould. The heat is suffocating in the deep and dark recesses of these primeval woods, where not a breath of air penetrates, and where, after being drenched by the periodical rains, the damp is so excessive that a blue mist rises in the early morning among the huge stems of the trees, and envelops the entangled creepers stretching from bough to bough. A deathlike stillness prevails from sunrise to sunset, then the thousands of animals that inhabit these forests join in one loud discordant roar, not continuous, but in bursts. The beasts seem to be periodically and unanimously roused by some unknown impulse, till the forests ring in universal uproar. Profound silence prevails at midnight, which is broken at the dawn of morning by another general roar of the wild chorus. The whole forest often resounds when the animals, startled from their sleep, scream in terror at the noise made by bands of its inhabitants flying from some night-prowling foe. Their anxiety and terror before a thunder-storm is excessive, and all nature seems to partake in the dread. The tops of the lofty trees rustle ominously, though not a breath of air agitates them; a hollow whistling in the high regions of the atmosphere comes as a warning from the black floating vapour; midnight darkness envelops the ancient forests, which soon after groan and creak with the blast of the hurricane. The gloom is rendered still more hideous by the vivid lightning, and the stunning crash of thunder."

One of the most interesting subjects, of which mention is made in the work before us, is the gradual elevation and subsidence observed in some portions of these continents themselves. Just when the imagination had become somewhat familiar with the sudden but very partial upheaving of the earth by volcanic agencies, this new discovery came to light of the slow rising and sinking of vast areas of the land, and unaccompanied with any earthquakes or volcanic eruptions. In some parts the crust of the earth has sunk and risen again; in others, sort of see-saw movement on a most gigantic scale has been detected.

"There is a line crossing Sweden from east to west, in the parallel of 56° 3´ N. lat., along which the ground is perfectly stable, and has been so for centuries. To the north of it for 1000 miles, between Gottenburg and North Cape, the ground is rising; the maximum elevation, which takes place at North Cape, being at the rate of five feet in a century, from whence it gradually diminishes to three inches in a century at Stockholm. South of the line of stability, on the contrary, the land is sinking through part of Christianstad and Malmo; for the village of Stassten in Scania is now 380 feet nearer to the Baltic than it was in the time of Linnæus, by whom it was measured eighty-seven years ago."

It is evident that the elevation of the land, in relation to the level of the sea, may be produced either by an uprising of the continent or a depression of the bed of the ocean, permitting the waters to sink; as also the apparent depression of the land may be occasioned by an elevation in the bed of the ocean. This renders the problem somewhat more difficult to solve, because the causes we are seeking to discover may be sometimes operating at that part of the crust of the earth which is concealed from our view. Mr Lyell, who, in his Principles of Geology, has collected and investigated the facts bearing upon this subject, mentions the following as probable causes of the phenomena: —

1. "It is easy to conceive that the shattered rocks may assume an arched form during a convulsion, so that the country above may remain permanently upheaved. In other cases, gas may drive before it masses of liquid lava, which may thus be injected into newly opened fissures. The gas having then obtained more room, by the forcing up of the incumbent rocks, may remain at rest; while the lava, congealing in the rents, may afford a solid foundation for the newly raised district.

2. "Experiments have recently been made in America, by Colonel Patten, to ascertain the ratio according to which some of the stones commonly used in architecture expand with given increments of heat… Now, according to the law of expansion thus ascertained, a mass of sandstone, a mile in thickness, which should have its temperature raised 200° F., would lift a super-imposed layer of rock to the height of ten feet above its former level. But, suppose a part of the earth's crust one hundred miles in thickness, and equally expansible, to have its temperature raised 600° or 800°, this might produce an elevation of between two and three thousand feet. The cooling of the same mass might afterwards cause the overlying rocks to sink down again, and resume their original position. By such agency, we might explain the gradual rise of Scandinavia, or the subsidence of Greenland, if this last phenomenon should also be established as a fact on further inquiry.

3. "It is also possible that, as the clay in Wedgwood's pyrometer contracts, by giving of its water, and then by incipient vitrification; so large masses of argillaceous strata, in the earth's interior, may shrink, when subjected to heat and chemical changes, and allow the incumbent rocks to subside gradually. It may frequently happen that fissures of great extent may be formed in rocks, simply by the unequal expansion of a continuous mass heated in one part, while in another it remains in a comparatively low temperature. The sudden subsidence of land may also be occasioned by subterranean caverns giving way, when gases are condensed, or when they escape through newly formed crevices. The subtraction, moreover, of matter from certain parts of the interior, by the flowing of lava and of mineral springs, must, in the course of ages, cause vacuities below, so that the undermined surface may at length fall in."[16 - Lyell's Principles of Geology, p. 536.]

Two agencies of the most opposite, character have apparently been, at all times, acting on the crust of the earth to change its form, or add to the surface of dry land – the volcano and the insect! – the one the most sudden and violent imaginable, producing in a short time the most astonishing effects; the other gradual, silent, and imperceptible, yet leaving the most stupendous monuments of its activity. The volcano has thrown up a mountain in a single night; there is an instance, too, on record, where a mountain has quite as suddenly disappeared, destroying itself in its own violent combustion, and breaking up with repeated and terrific explosions. On the other hand, besides what has been long known of the works of the coral insect, the microscope has revealed to us that huge cliffs have been constructed of the minute fossil shells of animalcule. These creatures, abstracting from the water, or the air, or both, the minute particles of vegetable or other matter they hold in solution, first frame of them their own siliceous shells, and then deposit these shells by myriads, so as ultimately to construct enormous solid mounds out of imperceptible and fluent particles.

Astonishing, indeed, is the new world of animals invisible to the naked eye, which science has lately detected.

"Professor Ehrenberg," says Mrs Somerville, "has discovered a new world of creatures in the infusoria, so minute that they are invisible to the naked eye. He found them in fog, rain, and snow, in the ocean and stagnant water, in animal and vegetable juices, in volcanic ashes and pumice, in opal, in the dusty air that sometimes falls on the ocean; and he detected eighteen species twenty feet below the surface of the ground in peat earth, which was full of microscopic live animals: they exist in ice, and are not killed by boiling water. This lowest order of animal life is much more abundant than any other, and new species are found every day. Magnified, some of them seem to consist of a transparent vesicle, and some have a tail; they move with great alacrity, and show intelligence by avoiding obstacles in their course: others have siliceous shells. Language, and even imagination, fails in the attempt to describe the inconceivable myriads of these invisible inhabitants of the ocean, the air, and the earth."

With every great change, however brought about, in the surface of the earth, and the climate of its several regions, it appears that, either by the direct agency of the Omnipotent Creator, or through the intermediate operations of laws which are at present profound secrets to us, a corresponding change takes place in the forms of animal life, and in the whole vegetable kingdom. Modern science presents no subject to us of more interest than this, and none apparently so inscrutable. Nor does the examination of the globe, as it exists before us at this moment, with its various floras and faunas, at all assist us in forming any conception of the law by which the geological series (if we may so term it) of animal life, has been regulated, for the distribution of the several animals over the several countries and climates of the world follows no rule that one can detect. Of course, no animal can exist where provision has not been made for its subsistence, but the provision has been made with the same abundance in two countries, and in the one the animal is found, and the other not. We should ask in vain why the horse was found a native of the deserts of Tartary, and why it was originally unknown to the plains of America? Nor can any cause be detected for the difference between the congeners, a representative species of one continent or island, and those of another. And not only have the larger animals an arbitrary territory marked out to them by nature, but birds, and even insects, are separated and grouped together in the same unaccountable manner. The chapters which Mrs Somerville has devoted to this subject will be read, especially by those to whom the topic is new, with extreme interest. They are enlightened and judicious.

It is a natural supposition to make, that, in the series of animals which at great geological periods have been introduced upon the earth, there has been a progression, so that each new form of animal life has been, in some marked manner, superior to that which is substituted. The comparative anatomist has not sanctioned this opinion; he tells us that he finds the same "high organisation" in the fossil saurians of a bygone world, as in the lions and leopards of the present day. But we would observe that the presence of this "high organisation" is not sufficient to determine the question. We should be surprised, indeed, if any creature were to be found whose structure was not perfectly adapted to the mode of life it was destined to lead. But it is permissible to compare one animal with another in its whole nature, and the character of its existence. The pig has the same high organisation as the dog, yet we should certainly prefer the one animal to the other; we should say that it was calculated for a happier life. We cannot suppose that a bird is not a more joyous creature than the worm or the snail. The adaptation of the whole form and structure to a pleasurable existence, and not what is termed high organisation, is that which we must regard, in estimating the superiority of one animal to another. Now, in this respect, there surely has been a progression from the earliest epochs. The crocodile and the tortoise are, amongst the animals which now exist, those which most resemble some of the more remarkable of the extinct genera. They are as perfectly adapted, no doubt, as any other creature, to their peculiar mode of being; but that mode of being is not an enviable one. The long stiff unwieldy body of the one, and the slow movement, with the oppressive carcase, of the other, are not consistent with vivid animal enjoyment. The crocodile, accordingly, lies motionless for hours together —waits for its prey – and slumbers gorged with food. And for the tortoise, it appears to lead a life as near to perpetual torpor as may be. Pass through a museum, and note those huger animals, the elephant and the rhinoceros, the seal or walrus, all those which most remind us of the gigantic creatures of the antediluvian world, and compare them with the horse, the deer, the dog, the antelope. Surely the latter present to us a type of animal life superior to the former – superior, inasmuch as the latter are altogether calculated for a more vivacious, sprightly, and happy existence. We must not venture to remark on their greater comparative beauty, for we shall be told that this is a matter for our own peculiar taste. We should not be contented to be so easily silenced on this head, but we should require far more space than we have now at our disposal to defend our æsthetic notions.

We have found ourselves imperceptibly conducted from the inanimate to the animate creation; we shall proceed, therefore, with the same topic, in the few farther extracts we shall be able to make from the work before us. Indeed, with so vast a subject, and so brief a space, it would be idle to affect any great precision in the arrangement of our topics; enough if they follow without abruptness, and are linked together by natural associations of thought.

"Three hundred thousand insects are known!" and every day, we were almost going to add, increases the number. They abound, as may be expected, in equatorial regions, and decrease towards the poles. "The location of insects depends upon that of the plants which yield their food; and as almost each plant is peopled with inhabitants peculiar to itself, insects are distributed over the earth in the same manner as vegetables; the groups, consequently, are often confined within narrow limits, and it is extraordinary that, notwithstanding their powers of locomotion, they often remain within a particular compass, though the plant, and all other circumstances in their immediate vicinity, appear equally favourable for their habitation."

Mountain-chains, Mrs Somerville observes, are a complete barrier to insects; they differ even in the two sides of the Col de Tende in the Alps, and they are limited in the choice of their food. If a plant is taken to a country where it has no congeners, it will be safe from the insects of that country; but if it has congeners, the insect inhabitants will soon find the way to it. Our cabbages and carrots, when transplanted to Cayenne, were not injured by the insects of that country; and the tulip tree, and other magnolias brought here, are not molested by our insects.

The insect is a race, or order, of creatures not friendly to man, or any of the larger animals.

"The mosquito and culex are spread over the world more generally than any other tribe; they are the torment of men and animals from the poles to the equator, by night and by day; the species are numerous, and their location partial… Of all places on earth, the Orinoco, and other great rivers of tropical America, are the most obnoxious to this plague. The account given by Baron Humboldt is really fearful; at no season of the year, at no hour of the day or night, can rest be found; whole districts in the Upper Orinoco are deserted on account of these insects. Different species follow one another with such precision, that the time of day or night may be known accurately from their humming noise, and from the different sensations of pain which the different poisons produce. The only respite is the interval of a few minutes between the departure of one gang and the arrival of their successors, for the species do not mix. On some parts of the Orinoco, the air is one dense cloud of poisonous insects to the height of twenty feet."

The sea, as well as the air, is populous with insect life. The discoloured portions of the ocean generally owe their tint to myriads of insects. The vermilion sea off California is probably to be accounted for from this cause, "as Mr Darwin found red and chocolate-coloured water on the coast of Chili, over spaces of several square miles, full of microscopic animalcules, darting about in every direction, and sometimes exploding" – we hope for joy. "In the Arctic seas, where the water is pure transparent ultramarine colour, parts of twenty or thirty square miles, one thousand five hundred feet deep, are green and turbid, from the quantity of minute animalcules. Captain Scoresby calculated that it would require eighty thousand persons working unceasingly, from the creation of man to the present day, to count the number of insects contained in two miles of the green water."

Captain Scoresby must be very fond of calculations. We have noticed, by the way, on several occasions, how very bold these men of figures are! One pounds and pulverises the Pyrenees, and strews them over France, and tells us how many feet this would raise the level of the whole country. Another calculates how much soil the Mississippi brings down, per hour, to the ocean; and another, still bolder, undertakes to say what quantity of ice lies amongst the whole range of the Alps. Some of these calculations are laborious inutilities, as it is evident that no accurate data can be obtained to proceed upon. In the last instance, how find the depth of the ice? The sand of the desert has been sounded in one place, we are told, and the lead has sunk three hundred and sixty feet without finding a bottom; but what plummet can sound the glacier? Here and there a crevice may let us into the secret of its depth, and we know that below a certain level ice cannot remain unmelted; but who can tell the configuration of the mountain under the ice, how shallow the glacier may be in some parts, and into what profound caverns it may sink in others? There is something childish in giving us an array of figures, when the figures present no useful approximation to the truth.

We have alluded to the difficult problem of the distribution of the different species of animals throughout the several regions of the globe: the same problem meets us in the vegetable world. Here we might expect to grapple with it with some better hopes of success, yet the difficulties are by no means diminished; we only seem to see them more plainly. In the first place, it is clear, as Mrs Somerville says, that "no similarity of existing circumstances can account for whole families of plants being confined to one particular country, or even to a very limited district, which, as far as we can judge, might have grown equally well in many others." But the difference of the floras is not the only difficulty. While there is difference in a great number of the species, there is identity in a certain other number. If now we account for the difference by supposing that the several portions of land emerged from the ocean at different epochs, and under different conditions, and that, therefore, the generative powers of vegetable life, (in whatever, under the will of Divine Providence, these may be supposed to consist) manifested themselves differently, how shall we next account for this identity? "In islands far from continents, the number of plants is small; but of these a large proportion occur nowhere else. In St Helena, of thirty flower-bearing plants one or two only are native elsewhere." But these one or two become a new perplexity. "In the Falkland Islands there are more than thirty flowering plants identical with those in Great Britain." Very many similar cases might be cited; we quote these only to show the nature of the difficulty with which science has to cope.

And here comes in the following strange and startling fact, to render this subject of vegetable production still more inexplicable: —

"Nothing grows under these great forests, (of South America;) and when accidentally burnt down in the mountainous parts of Patagonia, they never rise again; but the ground they grow on is soon covered with an impenetrable brushwood of other plants. In Chili the violently stinging Loasa appears first in these burnt places, bushes grow afterwards, and then comes a tree-grass, eighteen feet high, of which the Indians make their huts. The new vegetation that follows the burning of primeval forests is quite unaccountable. The ancient and undisturbed forests of Pennsylvania have no undergrowth; and when burnt down they are succeeded by a thick growth of rhododendrons." – (Vol. ii. p. 190.)

But we must bring our rambling excursion through these pleasant volumes to a close; the more especially as we wish once more to take this opportunity, not as critics only, but as readers also, to express our grateful sense of the benefit which Mrs Somerville has conferred upon society by this and her preceding volume, The Connexion of the Physical Sciences. It was once a prevailing habit to speak in a sort of apologetic strain of works of popular science. Such habit, or whatever residue of it remains, may be entirely laid aside. If by popular science is meant the conveyance, in clear intelligible language, as little technical as possible, of the results of scientific inquiry, then are we all of us beholden more or less to popular science. The most scientific of men cannot be equally profound in all branches of inquiry. The field has now become so extensive that he cannot hope to obtain his knowledge in all departments from the first sources. He must trust for much to the authority of others. Every one who is desirous of learning what anatomy and physiology can teach us, cannot attend the dissecting table. How much that we esteem, as amongst the most valuable of our acquisitions, depends on this secondary evidence! How few can follow the calculations of the mathematician, by which he establishes results which are nevertheless familiar to all as household words! And the mathematician himself, great aristocrat as he is in science, must take the chemist on his word for the nice analysis the latter has performed. He cannot leave his papers to follow out experiments, often as difficult and intricate as his own calculations. Indeed the experiments of the man of science have become so refined and elaborate, and deal often with such subtle matter, and this in so minute quantities, that, as it has been said of the astronomer, that it requires a separate education, and takes half a life to learn to observe, so it may be truly said, that to devise and conduct new experiments in philosophy has become an art in itself. We must be content to see a great deal with the eyes of others; to be satisfied with the report of this or that labourer in the wide field of science. We cannot all of us go wandering over moor and mountain to gather and classify herbs and flowers; interested as we all are in geological speculations, we cannot all use the geological hammer, or use it to any purpose; still less can we examine all manner of fishes, or pry with the microscope into every cranny of nature for infusoria.