THE NEW EDITION OF LYELL'S GEOLOGY.* [Futsr NoricE.] IN directing

the attention of our readers to the new edition of Sir Charles LyeIfs Principles of Geology, it may be well to remind those of them who have not read the other works of Sir C. Lye]l on this subject that this is a distinct work from the Elements of Geology, and to point out the manner in which the subjects treated of in these two books differ. The Elements of geology is a work on the changes of ancient date in the earth's surface, which is defined to be the subject of geology proper. The Princi- ples of geology treat of the modern analogous changes as illustra- tive of geology proper. But seeing that the analogy is so constant, and the similarity both of the method of treating of each subject, and of the subjects themselves, is so great, a good deal of preliminary discussion and argument will naturally be found common to both treatises. The difference is thus stated :- "The 'Principles' and 'Elements,' thus divided, occupy, with ono exception, very different ground. The Principles treat of such por- tions of the economy of existing nature, animate and inanimate, as are illustrative of geology, so as to comprise an investigation of the perma- nent effects of causes now in action, which may serve as records to after ages of the present condition of the globe and its inhabitants. . . . .In the Elements of Geology, on the other hand, I have treated briefly of the component materials of the earth's crust, their arrangement and relative position, and their organic contents, which, when deciphered by aid of the key supplied by the study of the modern changes above alluded to, reveal to us the annals of a grand succession of past events —a series of revolutions which the solid exterior of the globe, aud its living inhabitants, have experienced in times almost entirely antecedent to the creation of man."

It is also remarked that while the two branches of study are inseparably connected, the modern changes may be, perhaps, the best part of the subject with which to begin the study of geology.

It will be seen that this tenth edition follows the ninth at an in- terval of more than thirteen years, it will therefore not be surprising to the reader to find considerable additions and alterations, embody- ing the discoveries made during that period, and their effect on the previous line of argument. It will be remembered that in the ninth and previous editions the subject of the progressive develop- ment of organic life had been presented to the reader, and that on this, as well as on the causes and proofs of the vicissitudes of climate in epochs anterior to history, there was a good deal of careful and elaborate discussion. It may be well to state at once that chaps. ix. to xiii. of the tenth edition, in which these subjects are treated of, are either rewritten or entirely new. Considerable additions have also been made (chap. xxvi., vol. ii.) to the dis- cussion on the structure of Mount Etna, and several descriptions of recent earthquakes and new facts illustrative of volcanic agency have been introduced.

But it is in the third book, on the changes of the organic world now in progress, including the subject of species, their transmuta- tion, origin, distribution, inigratiou, and extinction, that most will be found that is entirely new both in matter and method. Such being generally the distribution of the new matter presented to us in this edition, there are also a few scattered remarks in the least altered portions of the book which are of an interest that will claim for them special notice.

The first six chapters of the former editions have been reprinted with no alteration, except that the sixth is transposed and becomes the tenth, while the eleventh, twelfth, and ninth of previous editions reappear as the seventh, eighth, and ninth of the new edition, not being altered, but containing some stray facts contri- buted by recent discoverers.

With regard to the theory of progressive development treated of in the ninth chapter, it may be useful to sketch the present line of argument. Recent discoveries having led to the tracing back of the metnorials of oar race one step farther into the past, it is the object of the author to show that the evidence in favour of "the modern date of the human era, as compared with that of a vast series of antecedent epochs, each of them characterized by distinct species of animals and plants," has not been shaken. And one main element of the argument appears to be the similarity of the conclusions which are arrived at by the separate study of (1) fossil plants, (2) fossil animals, vertebrate and invertebrate, (3) mammalia, and by the comparison of them all. The result of the induction is thus stated :—

" We have been fairly led by palreontological researches to the Con- clusion that the invertebrate animals flourished before the vertebrate, and that in the latter class fish, reptiles, birds, and mammalia made their appearance in a chronological order analogous to that in which they would be arranged zoologically according to an advancing scale • Principles of Geology or, the Modern Changes of the Earth and its Inhabitants Con- sidered as Illsutratire of Geology. By Sir Charles Lyell, Bart., M.A., F.R.S. Tenth and entirely revised edition. 2 vols. London: Murray. 1867. of perfection in their organization. In regard to the mammalia them- selves, they have been divided by Professor Owen into four sub-classes by reference to modifications of their brain. In the two lowest, called Lyencephala and Lissencephala, are included the marsupials and in- sectivore, and these have been met with fossil in the secondary rocks. Next above them in grade are the Gyrencephala, in which Cetaceans,. Proboscidians, Ruminants, Carnivore, and Quadrnmana are classed, all of which are found fossil in tertiary strata. Among these the Quad- rumana rank highest, and the Anthropomorphous family takes the lead in organization and instinct among the Quadrumana, coming also last in the order of time. To crown the whole, the series ends with the fourth great sub-class, the Archencephala, of which man is the sole repre- sentative, and of which the fossil remains have not yet been detected lit deposits older than the post-tertiary."

It is added that the human species being the most cosmopo-

lite and capable of surviving vicissitudes in climate and changes in physical geography among all the mammalia, it might have been expected that vestiges of it would be traced back as far as those of any existing species. It must also be remembered that works of art composed of indestructible materials would outlast almost all the organic compounds of rudimentary rocks. And it seems to be a fair assumption that the reasoning powers, which are the main distinguishing characteristic of the human species, would necessitate the coexistence of some works of art with very early, if not with the very earliest, specimens of the species so distin- guished. There is also a point of no less significance now than in the time of Anaximander, viz., that the protection of man from other species of equal number and of greater strength depended on his reason, and not on physical superiority, as "it is by no means clear that the organization of man is such as would confer a decided pre-eminence upon him, if in place of his reasoning powers he was merely provided with such instincts as are possessed by the lower animals."

An objection is alluded to which it would not be right to pass over, but which appears to admit of a satisfactory reply, namely, that the interference of the human species might be thought so wide a deviation from the antecedent course of physical events, that the knowledge of such a fact would tend to destroy all our con- fidence in the uniformity of the order of nature, both in regard to time past and future. Other changes equally extraordinary might happen from time to time. But "we have no reason to suppose that when man first became master of a small part of the globe, a greater change took place in its physical condition than is now experienced when districts never before inhabited become successively occupied by new settlers ; " and accordingly," we may suppose the general condition of the globe immediately before and after the period when our species first began to exist to have been the same, with the exception only of man's presence."

An interesting fact is introduced in chap. x. bearing on the proof of great vicissitudes of climate. The fact of the preservation of animal and vegetable substances by incarceration in ice is well known, and has of late years been practically tested in connection with accidents among the Alpine glaciers. The same cause has been the means of preserving in Russia and Siberia many skeletons of mammoths retaining the skin and hair. And the preservation of these animals has a double interest, in that it not only gives specimens of a species of great antiquity in a comparatively good state of preservation, but the circumstance that the soft parts of the animal have remained undecomposed proves that the ice or congealed mud in which the bodies of such quadrupeds were enveloped has never once been melted since the day when they perished. It is curious that the heads of most of them are said to have been turned towards the south. In this chapter, also, facts are adduced to prove that there is evidence on the East coast of England, as also in Switzerland, of two glacial periods, with an intervening period of greater warmth, which must have been of considerable duration, if we may judge from the thickness of the beds of lignite for the formation of which it gave time.

We will not do more than allude to the discussion of the effect on the climate of the earth produced by astronomical causes, such as the precession of the equinoxes and variations in the excentricity of the earth's orbit, because the subject being now introduced for the first time, it would be im- possible in the space at our disposal to give any adequate idea of the question. But it must be mentioned in passing that a memoir by Mr. J. Croll, published in 1864, is discussed, and elicits

our author's reasons for differing from him in some material points ; and that a table is inserted showing the excentricity of the earth's orbit at intervals of 50,000 years, calculated up to 1,000,004 years before 1800 A.D. ; and the corresponding number of winter days in excess of the summer days (the winter days being counted when the earth was at the part of the orbit furthest from the sun, and the summer when at the other extreme), and the correspond-

ing mean temperature of the hottest and coldest months taken under the same circumstances. Without going into the details of the discussion, it may be interesting to our readers to know that in one line (that for 850,000 years before 1800 A.D.), the varia- tion of temperature between those two months is stated as 133° Fahrenheit, the mean temperature of the hottest month being 126° Fahr., or 94 degrees above freeiing point, and that of the coldest month, —.7° Fahr., or 39 degrees below freezing point. It is sug- gested that for various reasons a probable period in which we may suppose that the incarceration in ice mentioned above may have taken place would be from 200,000 to 210,000 years before 1800 A.D.

A most interesting account is given, accompanied by an engrav- ing, of the earth pillars at Ritten, in the Tyrol, near Botzen, illus- trating the geographical effect of rain as distinguished from running water ; and in connection with the geological action of glaciers both in Switzerland and Scotland, an account is inserted of the Marjelen See, near the great Aletsch Glacier, a lake which is periodically drained by changes in the internal structure of the glacier.

At the end of the eighteenth chapter a discussion is introduced on the Delta of the Nile, in which it is mentioned that a piece of burnt brick has been found in the lowest layer of mud, next to the desert sand deposited 13,496 years before the year 1850, when the discovery was made.

A phenomenon is noticed as occurring at the mouths of the Mississippi, which Sir C. Lyell says is without parallel, as far as he is aware, in the delta of any other river. The muddy bottom of the sea off the mouths of that river rises up to the height of sometimes ten or eighteen feet above the level of the sea, and from the tops of these new-made islands gush springs of salt or brackish and muddy water, together with a considerable quantity of carburetted hydrogen or inflammable gas, the tubular cavities up which the springs rise being about six inches in diameter, vertical, and as regular in form as if bored by an auger. The following account of the origin of these lumps is interesting, as compared with an analogous phenomenon noticed below :—

" The initiatory moving power may probably be derived from the downward pressure of the gravel, sand, and sediment accumulated dur- ing the flood season off tho various mouths or passes, upon a yielding bottom of fine mud and sand. This now deposit forms annually a mass of no less than one mile square, having a thickness of twenty-seven feet. It consists of mud, coarse sand, and gravel, which the river lets fall somewhat abruptly when it first comes in contact with the still salt water of the gulf. A cubic mass of such enormous volume and weight thrown down on a foundation of yielding mud, consisting of materials which, as being very fine and impalpable, had long before been carried out farthest from the land, may well be conceived to exert a downward pressure capable of displacing, squeezing, and forcing up laterally some parts of the adjoining bottom of the gulf, so as to give rise to now shoals and islands. Railway engineers are familiar with the swelling up of a peat moss or the bed of a morass, on some adjoining part of which a new embankment has been constructed. I saw an example of this in the year 1839, in the Loch of Rescobie, in Forfarshire, five miles east of the town of Forfar. That lake had been partially drained, and the railway mound was carried over newly exposed, soft, and swampy ground, which gave way so as to let the mound sink down fifteen feet. It then became necessary to pile up additional matter fifteen feet thick in order to obtain the required level. On one side of the embankment, the bog, when I visited the place, bad swollen up in a ridge forty feet long and eight feet high, the upper portion consisting of peaty matter traversed by numerous willow roots. In the highest part of this upraised mass were several irregular cracks about six feet in their greatest width, and open for a depth of two yards or mere. On the opposite side of the railway mound, and about 100 yards distant from it, in the middle of what remained of the half-drained loch, a new island or 'mud lump' was seen, which had begun to rise slowly in 1837, and had attained before 1840 a height of several yards, with a length of about 100 feet, and a width of twenty-five feet. It was still strewed over with dead fresh-water mussels and other shells, but many land plants had already sprung up, so that its surface was green We need feel no sur- prise at the quantity of gaseous matter disengaged from cracks in these newly raised islands, when we recollect that almost everywhere in Europe, where a successful Artesian boring has been made, the water at first spouts up to a height far beyond that to which it would be carried by simple hydrostatic pressure. A portion of the propelling force usually consists of atmospheric air and carbonic acid gas, which last is generated by the decomposition of animal and vegetable matter. Of the latter there must be always a great store in the recent deposits of a delta like that of the Mississippi, as they enclose much drift timber at all depths, and the pent-up gaseous matter will be ready to escape wherever the overlying impervious clays are upheaved and rent."