to the molten ocean seething within the globe, and forcing its way out from time to time." When the crust of the earth was too thin to oppose much resistance to the outbreak of these internal fires, they so constantly forced themselves through, that some of the earlier rock deposit is perforated with numerous chimneys, narrow tunnels as it were, bored by the liquid masses that poured out through them.

But even that thin crust, how could it be formed? Astronomy, says Professor Agassiz, shows our planet thrown off from the central mass of which it once formed a part, to move through spaces cold enough to chill its surface. The first effect of cooling was contraction of its surface into a solid film or crust. That crust would shrink as the cooling continued, wrinkles and folds would arise in it. Here and there, where the tension was too great, there would be cracks. Meanwhile, the crust would thicken gradually as the mass within became affected by the outside temperature.

of the elements of earth which Professor Cotta, in his Lithology, speaks of as "a perpetual circulation of matter in the world of rocks."

On this head we will quote a passage from Professor Cotta's book. The second edition of that thoroughly clear, full, and systematic treatise upon Rocks has, this year, been translated by Mr. P. H. Lawrence into an English edition that includes the author's new material, and other information which the translator himself has added with the author's sanction. This is a part of Professor Cotta's summing up of his subject:

If we take a general review of the various formations and transformations of rock, we shall discover in them a perpetual process of circulation or rotation of substances, and of their different states. The substances remain, but the forms in which they appear and the mode of their combinations vary.

Disregarding for the moment the first solid products of cooling on the earth's surface, as not being capable of indentification at the present day, we may most conveniently enter the circle of transmutations with the eruptive igneous rocks, as approaching most nearly to original formations. These, then, are constantly attacked and decomposed by chemical and mechanical forces acting from their surface inwards, and from their cracks and fissures outwards.

rock-salt. By mechanical agency, on the other hand (partly aided by organic processes), there arise the much more important and extensive deposits of clay, sand, pebbles, marl, limestone, and dolomtie; and during the process of deposit, carbon (in the form of carbonic acid from the atmosphere), water, chlorine, and some other substances, are added to the previously existing

The cooling that solidified some of the constituents of earth, caused also the rising of vapours, their condensation into clouds, the falling of rains, the gathering of waters upon the face of the earth. As soon as the wash of an ocean wore the surface of the solid crust, it swept material from it to be deposited as sand, or mud, or pebbles at its The products of this decay are deposited bottom, layer upon layer. So the crystal- either in the form of chemical precipitates or line fire-born rocks were covered in many mechanical aggregates. By chemical process places with layer upon layer of the deposit of precipitation cavities and fissures in rocks befrom the waters which had reduced some come filled up (amygdaloids and veins), deposits part of them to a fine dust. So came the are made at the mouths of springs of limestonegreat division between unstratified and tuff, siliceous-tuff, bog-ore, &c.; or else other stratified, igneous and aqueous rocks. Be-crystalline rocks are formed, such as gypsum or tween them in character are the stratified rocks that have been metamorphosed, more or less recrystallized by heat. Where the molten mass from within has, through crack in the surface or otherwise, come into contact with, and partially melted, rocks deposited by water, clay has been baked into slate, limestone fused into crystalline marble. The geology of Professor Agassiz is decidedly too much of the convulsive school, when he says that "all mountains and mountain chains have been upheaved by great convulsions of the globe, which rent asunder the surface of the earth, destroyed the animals and plants living upon it at the time, and were then succeeded by long intervals of repose." As to the first part of the story of the globe, in fact, we prefer the teachings of Sir Charles Lyell to those of Professor Agassiz. Cosmical operations, mighty in their results, have for the most part been gradual as those rearrangements

materials.

But, like the eruptive masses, all these deposed and washed away by external forces, posited masses in their turn are partly decomand in other parts they become greatly changed internally by pressure and the action of heat. By means of heat and pressure acting during long periods, parts which thus in the first instance were only mechanically bound together, enter into new chemical combinations with each other, and assume a crystalline state more or less analogous to that of the crystalline mineral able in many cases that the substance of these aggregates of the eruptive rocks. It is even probderivative rocks has been fused and become eruptive a second time.

Thus the process of destruction and new

processes.

This is the perpetual circulation of matter in the world of rocks.

In the course of such various and renewed working up and transformation of the same substances, with the addition of those others furnished by the air and water, it cannot be matter of wonder that the variety of their groups has been always somewhat on the increase; for, if certain processes in this rotation are altogether universal in their character, recurring in the same way, everywhere and in every age, yet in consequence of the general multiplication of conditions and circumstances, and the increasing aggregate of their results, special combinations of the same processes have constantly arisen in later times and brought about special formations of rocks which were not previously in existence, or which do not belong to the normal phenomena of nature.

A

formation of rocks, be it ever so slow, and | and "the Silurian Beach" is, therefore, the therefore difficult of observation, has never, at subject of his second chapter. Around the any time of the earth's history, been interrupted, city of Cincinnati, Silurian shells and crusbut continues at the present day; and not only tacea may be collected by cartloads. is this true of the original formations, but the new products of consolidation, of deposits, and find it difficult to gather along any modern naturalist, says Professor Agassiz, would of transmutation, have always been equally subjected, and are still subject, to the same seashore, even on tropical coasts, so rich a harvest in the same time, as he will bring t home from an hour's ramble outside that city. His next chapter is upon "the Fern Forests of the Carboniferous Period." The land of North America at the beginning of this period included Newfoundland and Nova Scotia, the greater part of New England, the whole of New York, a narrow strip along the north of Ohio, a great part of Indiana and Illinois, and nearly the whole of Michigan and Wisconsin. Within this region lie nearly all the Great Lakes. Between the elevations of the land were other inland seas changed by the rains to freshwater lakes, filled in the course of centuries with débris from their shores, and transformed at last to spreading marshes on which arose the gigantic fern vegetation of which the first forests chiefly consisted. What ferneries were they, to compare with the pretty collections that our ladies now collect in hothouse or Ward's case! One goes back to this primeval time with satisfaction for assurance that these new favourites of fashion really are one of the oldest families in the world; and then one comes back to 1866 with a welcome for a fern book by Mr. John Smith, who has been studying ferns at Kew since the year 1822, and has been at the making of the whole Kew collection.

This increase in variety of the products of later times is not confined to geological and mineral substances; a greater and more rapid increase has taken place in the organic world, where the forms of life have multiplied in an ever ascending ratio (partly in consequence of the change and increase of the conditions of existence from geological causes).

The processes of change, to which the outward conformation of the globe's surface is subject, likewise multiply more rapidly than mere strictly geological phenomena.

Reasoning, therefore, from the past and from analogy with other kingdoms, we must expect the species of rocks and kinds of rock-formation to go on increasing indefinitely for the future, as they have been increasing continually ever since the first solidification of our earth's crust.

The earliest American land, says Mr. Agassiz, was "a long narrow island, almost continental in its proportions, since it stretched from the borders of Canada nearly to the point where now the base of the Rocky Mountains meets the plain of the Mississippi Valley. We may still walk along its ridge and know that we tread upon the ancient granite that first divided the waters into a northern and southern ocean."

Then came the age called Silurian because Sir Roderick Murchison happened to study its remains in water upon land once ascribed to the Silures. In the Silurian age, says our author, the world, so far as it was raised above the ocean, was a beach,

Mr. Smith's book is a systematic enumeration and description of the cultivated ferns, with a history of the introduction of exotic ferns, instructions as to cultivation Such a book will be welcomed now by hunand the etymology of their ungainly names. dreds of amateur collectors, although filty years ago it would have had as much chance of a general sale as if it had been published in the carboniferous age for the use of the Cephalopods. Says Mr. Smith,

place in our gardens, and are in high favour Though Ferns now occupy a conspicuous with cultivators, it is only in comparatively recent times that they have been brought into notice. During the last century certain classes of plants came into fashion, and after a Thus: Tulips were once the rage. At the season of popularity again fell into disrepute. time of the establishing of the several provincial Botanic Gardens, all of which were founded upon a strictly botanical footing, though many of them have now, to a greater or less extent,

degenerated into places of amusement, the plants while to the south-east of it lay the central plain greatest demand were those of our New Hol- teau of France. Great Britain was not forgotland and Cape colonies, principally the Heaths, ten in this early world for a part of the Proteas, Aloes, and their kindred. "In after- Scotch hills, some of the Welsh mountains, and years, dealers obtained large prices for Cac- a small elevation here and there in Ireland, altuses; but, with the exception of a few of the ready formed a little archipelago in that region. easily-grown and most showy kinds, these are By a most careful analysis of the structure of the now scarcely saleable. Still more recently the rocks in these ancient patches of land, tracing all magnificent-flowering Orchids were promoted the dislocations of strata, all the indications of to the first place in our gardens; and though any disturbance of the earth-crust whatsoever, these may still be said to maintain their posi- Elie de Beaumont has detected and classified four tion, the expense attending their cultivation is systems of upheavals, previous to the Silurian so great that they are for the most part confined epoch, to which he refers these islands in the Azoic sea. He has named them the system of to the gardens of the wealthy. Ferns, on the contrary, may, as a general rule, be grown La Vendée, of Finistère, of Longmynd, and of The Mobihan. These names have, for the present in a comparatively inexpensive manner. discovery made by Mr. N. B. Ward, that these only a local significance,- being derived, like plants can be grown to great perfection in small so many of the geological names, from the ornamental closed cases (now well known as places where the investigations of the phenom"Wardian Cases"), suitable not only for the ena wore first undertaken; but in course of drawing-rooms of the wealthy but for humbler time they will, no doubt, apply to all the codwellings, renders it possible for amateurs to temporaneous upheavals, wherever they may indulge their love of Ferns without going to the be traced, just as we now have Silurian, Devoexpense of erecting hothouses and employing a nian, Permian, and Jurassic deposits in Ameristaff of gardeners; and it is to be hoped that ca as well as in Europe.. this will be the means of retaining them in favour and spreading them still wider.

The enumeration shows that at the present time above nine hundred exotic species of ferns are cultivated in the various public and private gardens in this country; and of these by far the greater number have been introduced during the last quarter of a century.

siz

From the old Fern Forests Professor Agas-
passes to the Mountains and their Ŏri-
come to the Growth of
gin. Then we
Continents. Here is the account given of
young Europe in the days when it was
growing up:

In the European ocean of the Azoic epoch we find five islands of considerable size. The Scandinavia largest of these is at the North. had even then almost her present outlines; for Norway, Sweden, Finland, and Lapland, all of which are chiefly granitic in character, were among the first lands to be raised. Between Sweden and Norway there is, however, still a large tract of land under water, forming an extensive lake or a large inland sea in the heart of the country. If the reader will take the trouble to look on any geological map of Europe, he will see an extensive patch of Silurian rock in the centre of Sweden and Norway. This represents that sheet of water gradually to be filled by the accumulation of Silurian deposits and afterwards raised by a later disturbance. There is another mass of land far to the south-east of this Scandinavian island, which we may designate as the Bohemian island, for it lies in the region now calted Bohemia, though it includes, also, a part of Saxony and Moravia. The north west corner of France, that promontory which we now called Bretagne, with a part of Normandy adjoining it, formed another island;

The Silurian and Devonian epochs seem to have been instrumental rather in enlarging the tracts of land already raised than in adding new ones; yet to these two epochs is traced the upheaval of a large and important island to the north-east of France. We may call it the Belgian island, since it covered the ground of modern Belgium; but it also extended considerably beyond these limits, and included much of the Northern Rhine region. A portion only of this tract, to which belongs the central mass of the Vosges and the Black Forest, was lifted which also enduring the Silurian epoch, larged considerably Wales and Scotland, the Bohemian island, the island of Bretagne, and Scandinavia. During this epoch the sheet of water between Norway and Sweden became dry land, a considerable tract was added to their northern extremity on the Arctic shore; while a broad band of Silurian deposits, lying now between Finland and Russia, enlarged that region.

The Silurian epoch has been referred by Elie de Beaumont to the system of upheaval called by him the system of Westmoreland and Hundsrück, again merely in reference to the spots at which these upheavals were first studied, the centres, as it were, from which the investigations spread. But in their geological significance they indicate all the oscillations and disturbances of the soil throughout the region over which the Silurian deposits have been traced in Europe. The Devonian epoch added greatly to the outlines of the Belgian island. To it belongs the region of the Ardennes, lying between France and Belgium, the Eifelgebirge, and a new disturbance of the Vosges, by which that region was also extended. The island of Bretagne was greatly increased by the Devonian deposits, and Bohemia gained in dimensions, while the central plateau of France remained much the same as before. The changes of the

IMMORAL BOOKS.

Devonian epoch are traced by Elie de Beaumont to a system of upheavals called the Ballons of the Vosges and of Normandy, so called from the rounded balloon-like domes characteristic of the mountains of the time. To the Carboniferous epoch belong the mountain-systems of Forey (to the west of Lyons), of the North of England, and of the Netherlands. These three systems of upheaval have also been traced by Ele de Beaumont; and in the depressions formed between their elevations we find the coal-basins of Central France, of England, and of Germany. During all these epochs, in Europe as in America, every such dislocation of the surface was attended by a change in the

animal creation.

The other chapters of this pleasant book of popular science are on the Geological Middle Age; the Tertiary Age and its Characteristic Animals; the Formation of Glaciers, their Progression, and their External Appearance; the glacies being discussed here generally with regard to their geological significance. But a special volume is to follow, in which Professor Agassiz will add to the excellent studies by Forbes, Tyndall, and others, of the glaciers of the old world, his own tracings of the glacial phenomena of America.

posed by bigotry upon youthful genius. The
real inference probably is, that the immo-
rality of a book is scarcely a matter for for-
mal argument; it must be decided by the
instinctive judgment of healthy minds. To
count up the breaches of conventional mo-
rality is a futile proceeding; for, as in the
case of shooting negroes, everything de-
pends upon the spirit in which the laws are
disregarded. No sort of test has hitherto
been devised for detecting the presence or
absence of so refined an essence as a virtu-
ous spirit, except the immediate effect which
contact with a work produces upon sound
mental senses.
There are certain books
which, as Mr. Carlyle says of a performance
of Diderot's, should cause their readers to
plunge into running waters and regard him-
self for the rest of the day as more than
ceremonially unclean. But to argue about
them is like arguing about a bad smell. If

an alderman swears that the Thames smells
sweet to him, no power on earth can prove
to him that it stinks.

Hence, a great deal of controversy upon such matters would really amount to a comparison of the moral idiosyncrasies of the contending critics. In the absence of any means of deciding this delicate point, we For the glaciers of Europe, he says, the cannot say whether the senses of one are broken character of the country, intersected morbidly sensitive, or those of the other morin every direction by mountain chains, pre- bidly dull, to immoral images. The legiti sents numerous centres of dispersion. Ow-mate form into which criticism runs is, ing to the extensive land-surfaces on the American continent, the same set of facts presents there a new aspect, enabling some new light to be thrown on the whole subject of glacial action.

From the Saturday Review.

IMMORAL BOOKS.

SOME recent discussions seem to indicate that the public mind is in a state of utter confusion as to the canons by which the morality of a literary work is to be decided. No satisfactory dogmas can be laid down. Those who are most inclined to a mistaken prudery feel the absurdity of drawing a line which would exclude Othello or Cymbeline. Their adversaries cannot quite venture to argue that, as the accusation of immorality has constantly been brought against the noblest writings, therefore every one accused of immorality is a noble writer, or that he has done anything instrinsically virtuous in breaking down the barriers im

"You must be immoral because I say so;" and the only reply is what vulgar boys express by "You're another." From this it follows that most of the ordinary arguments are beside the point. For example, the question whether a poem is or is not dramatic seems to be generally quite immaterial. It would, indeed, have some importance if we were discussing the character of the poet, as distinguished from that of his work. It would be important to prove, if any one could have any doubts upon the subject, that Shakspeare was not responsible for Iago's sentiments, and that Milton was not, beyond a certain point, to be identified with the devil. In criticising Byron or Shelley it would be more difficult and more interesting to inquire how far their poems expressed their own convictions; but it would be interesting only as affecting our judgment of Byron or Shelley, not as deciding the morality of Don Juan or Queen Mab. If a poet claims that he does not mean what he says, the claim may always be conceded; but it really makes no more difference than the assertion of Hume that he is not really arguing against Christianity when he tries to prove the incredibility of miracles. The ar