the North Pacific. It seems almost incredible to suppose that a Continent has been broken up since comparably recent times; but we shall presently see that other changes of quite as great geographical importance, have also transpired in the interval.

ocene period. All of them possess freshwater deposits, remarkable for their containing rich stores of fossil plants, marked by the same geographical peculiarities we have already noticed as characteristic of those in Switzerland, and elsewhere. Here we have proof that when the Old World and the New were joined by a continuous It may be asked, how it is that the flora tract of land, now more or less occupied which indicates a former land connection by the sea, that land was clothed, owing between Asia and America, is now printo the mild temperature, with a rich and cipally confined to the southern states of varied flora. As if to supplement the the latter country? Our next endeavour teachings of the Swiss lignite beds, as will be to answer this, and to point out yielded up to a careful study of the plants, that it was the gradual incoming of the the insects found associated with them are great northern winter, geologically known marked by similar geographical peculiar-as the "Glacial Epoch," which drove what ities, and include genera now as widely previously had been northern and temperscattered as the flora. The Oeningen ate animals and plants into more southerly beds have yielded over nine hundred spe- latitudes. The Pliocene period succeeded cies of fossil insects, whilst the entire number which has been obtained from all the beds of the upper and lower Miocene formations of Switzerland amount to more than thirteen hundred! Among them we find the white ants (Termites), now so peculiar to subtropical regions, as well as dragon-flies of the South African, and not European type. The Miocene strata of Austria have yielded fossil butterflies almost, if not quite, identical with Indian species.

the Miocene, and the organic remains peculiar to it are plainly marked by evidence of a gradual refrigeration of climature throughout the whole northern hemisphere. That the plants now living in such areas as South Carolina once had a more northerly extension, is proved by those very species being found fossil in strata of the Pliocene age in Tennessee and elsewhere. This fact not only indicates the way in which such a flora spread southerly, but connects living with Miocene species, and thus clearly establishes lineage.

These facts point clearly to the conclusion, that the reason why the Southern States of North America are now occupied A glance at the more ancient species of by a flora which was European during the animal life, from the mid-Tertiary period Miocene age, is that such flora migrated upwards, is full of interest, on account of thither by way of that continuous land its supplementing what has been clearly whose geographical as well as geological pointed out by a careful comparison of outliers are to be found in Japan, Kam- vegetable organic remains. We have alschatka, the Aleutian islands, Vancouver's ready noticed the singular agreement beIsland, &c. This generalization is borne tween the Swiss Miocene flora and its enout by a study of existing plants in some tomology, as regards their geographical of the localities mentioned. The most sig-character. Our next attention will be nificant of the facts is, that the further we go east in the Old World, the more numerous relatively do we find living species which occur fossilized in the Swiss lignites. The Salisburia-recently introduced into this country for its singularly graceful foliage is now limited to the Japanese regions, although it occurs in the fossil state in North America. There are more than three hundred existing species of plants common to the Southern portion of the United States and Japan than to Europe. So that in this respect Japan is more nearly related to the New World than it is to that of which it forms an easterly prolongation! The northerly plants common to Europe, Asia, and North America, are all found growing on the Aleutian islands, which, as before remarked, stretch across

given to the proofs that the same cause which drove the flora southerly, and isolated it in its present localities the cold of the Glacial period-operated equally on the animal kingdom, so that its geographical distribution may, in a great measure, be assigned to the same cause. In the Miocene beds of the Sewalik Hills, so admirably and patiently worked out by the late Dr. Falconer, we have numerous evidences of geographical conditions which have since then been wonderfully disturbed, and of animals living in India which have subsequently been distributed elsewhere. The giraffe and rhinoceros were then Indian, although they are now confined to Africa. Did space permit, other peculiarities might be mentioned of a similar nature. During the same period the monkey was a

European animal, and it is more than pro- submerged, to the depth of at least sevenbable that the last survivor of this group is teen hundred feet! Over the greater part represented by the rare, protected species of this tract were strewn the thick beds which inhabits the rock of Gibraltar. The of sand, gravel, and clay, termed by geolwell known Crags" of Norfolk and Suf- ogists the Northern Drift." Arctic molfolk represent the Pliocene period in Great lusca then lived in British seas in Arctic Britain. Among the hundreds of species proportions. Icebergs from the north, of fossil shells they include are forms now laden with "erratic "boulders, gravel, &c., living in the West Indian, Indian, and Jap-stranded in the shallower waters, and thus anese seas, and in the Pacific Ocean. introduced northern plants into Britain and Nothing could more plainly illustrate the Europe. The subsequent upheaval of the gradual increment of cold, than a compar- country, until dry land appeared, was ative study of the southern and northern doubtless quite as slow a process as that species of shells found in these three of submergence. In the south of Europe Crags." At the same time, their ele- we have proofs of even greater physical phantine, rhinocerine, and hippotamus re- disturbances than those which once more mains indicate how abundant these an-made Britain into a seabottom; whilst the imals were in England before the com- "drift" beds were forming in this counmencement of the Glacial Epoch. try, limestone beds were being laid down The Ice-cap, which evidently began to over what is now Sicily, and these were afform at the North Pole during the earlier terwards upheaved to three thousand feet part of the Pliocene period, gradually in- above the sea-level. A great portion of creased its area, and crept further south North Africa was then under water, the on all sides. Between the latest "Crag latter occupying the present desert of Sadeposit and the "Drift" beds - the latter hara. Here it was that the terrible burnof which were formed under undoubted ing sands were originally accumulated. Arctic conditions we have a sequence of British mollusca had migrated southerly, the most unbroken kind, which illustrates, driven thither by the encroaching cold, by its increased percentage of northern and taken up their positions in Sicilian and shells, how the cold was intensifying in African seas, just as the Arctic species had this country. At length we had a rigid occupied the English area. Hence they Arctic climate extending over mid-Eu- are found fossil, both in the Sicilian limerope. The Arctic species of animals and stones, and beneath the drifting sands of plants accompanied the physical ice inva- the African deserts. Most, if not all, the sion, until eventually Europe was peopled species of Rhinoceri, Hippopotami, Eleby them in the Old World, and the United phants, Hyæna, &c., passed over to AfStates of America in the New. The cli-rica, and Asia, where their descendants mate can be geologically proved to have still exist. Only those species remained intensified in the latter country, as we know it to have been the case in this. There still exists, in both areas, a few animals and plants which plainly tell of a continued land-connexion, and as lucidly point out the era of this land being broken up as occurring just before the Glacial period began, or during its progress. The common pike still lives in American, as well as in English rivers; the common heather has been found scantily blooming on the hills to the north of Boston, just as it purples the mountains of Scotland and England. Scarcely any difference can be detected between the American and European beavers, although the greater extended period of civilization in the Old World has encroached on its haunts, and thus almost rendered it extinct.

behind which could adapt themselves to the changed conditions. These appeared on the dry land, and spread themselves over that portion which was uplifted towards the close of the Glacial epoch. As the woolly-haired mammoth (Elephas primigenius) and woolly-haired rhinoceros, their remains are met with in post-glacial deposits, whilst in Northern Asia their tusks have accumulated to such a degree, and been so well preserved, as to form the

Ivory Mines" of Siberia! In the deeper and colder portions of the British seas there still exist, as Professor Edward Forbes pointed out, a few species of mollusca which came over during the great Arctic invasion, and having retained suitable habitats after the warmer conditions ensued, remained behind, to add the mite of their testimony The physical and geographical changes to the general mass of evidence. Perhaps which took place during this great north- one of the best illustrations of this influern winter were of a most extensive na-ence of the former Arctic climature upon ture. We have ample evidence that the the geographical distribution of animals, entire area of Great Britain was eventually is that given by Mr. Andrew Murray, in

ren

der the "struggle for existence" all the keener. It is estimated that the northern shores of the Baltic are being elevated at the rate of about three feet in a century, In one hundred thousand years this would elevate them as high as we know the Sicilian beds have been upheaved since the commencement of the Glacial epoch.

his elaborate work on the "Geographical | to cosmical agencies. An enormous amount Distribution of Mammals." Two species of physical change could be wrought in of seal are now living, one in the Caspian the period assigned by Croll, especially as sea, and the other in Lake Baikal. As is the rigorous climature and the encroach'well known, the latter is situated almost ment of the northern ice-cap over the in the centre of the great Asiatic conti- availabie area of occupation, would crowd nent. As its name implies, it is completely species more together, and thus isolated from any other body of water, as is also the case with the Caspian. Baikal is purely a fresh-water lake, whilst the Caspian has only one-third the ordinary saline properties of sea-water. The seals found living in these two great lakes belong, one of them to the same species as that still frequenting the northern shores of Britain, and the other to a species exceedingly abundant in the North Atlantic. We know that a depression of five hundred feet would once more bring the Arctic sea over the areas both of the Caspian and Lake Baikal. And we have seen that, during the Glacial period, Britain was submerged to more than three times that depth. We therefore quite agree with Mr. Murray, that the only way we can account for the presence of these seals in isolated bodies of fresh and nearly fresh water, is by supposing that when Northern Asia was uplifted from the bottom of the glacial sea, the two lowest hollows remained filled with water, in which the seals were shut off from their oceanic fellows. Their habits were subsequently altered, gradually, so suit their new conditions, and these, it would seem, were attended with certain varietal differences which distinguish them from their marine brethren. When the animals and plants of the That they flourish under such apparently Arctic and sub-arctic regions of the Old anomalous circumstances is evident by the and New Worlds are compared, one canfact that seal fisheries are profitably con-not but be surprised at their identity. All, ducted both in Lake Baikal and the Cas-or nearly all, belong to the same genera, pian Sea.

Important though the information thus furnished by the animal kingdom may be on geographical distribution, that afforded by Botany is even still more impressive. The geology of the "drift" beds enables us to understand how it was possible for Arctic floras to pass from Arctic regions so as to occupy the summits of even Equatorial mountains. Mr. Croll, from astronomical deductions, fixes the date of the Glacial period at two hundred and forty thousand years ago, and estimates its duration at one hundred and sixty thousand years. This calculation, although it has a good deal of probability about it, can only be regarded as provisional. There is, however, good reason for believing that the Glacial epochwhich was not the first our northern hemisphere had experienced was mainly due

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It was after the emergence of Europe from this Arctic sea, that floral migrations began more particularly to spread over her. The climate was still rigorous in its character, the snow-line coming down in the winter, probably to near the sea-level, as it now does in Greenland. Over the available area, arctic plants spread themselves, finding luxuriant habitats in the newly formed subsoils of the "drift." The hairy mammoth, woolly-haired rhinoceros, the Irish elk, the musk ox, reindeer, glutton, lemming, &c., more or less accompanied this flora, and their remains are always found in the post-glacial deposits of Europe, as low down as the South of France. In the New World, beds of the same age contain similar remains, indicating that they came from a common northern centre, and were spread over both continents alike.

whilst many of the species are common to the two great continents. This is most important in its bearing on our theory, as indicating that they radiated from a common centre after the Glacial period. When we explore the temperate regions of the same countries, we find the floral and faunal differences increasing, as one would expect in remembering that many of the species date from the Miocene epoch. In equatorial latitudes this contrast reaches its climax. No other theory will explain this peculiarity than that Arctic and subArctic species have spread since the Glacial epoch, whereas the southern and equatorial forms are older geographically, and were driven to their present areas of occupation by the slowly, but surely, advancing cold of the period in question.

The flora characteristic of Britain is marked by being opposed to extreme cold

the only

the occurrence of a European monkey on Gibraltar brings to our recollection the former extension of its race, of which it is now the single outlier.

on the one hand, and intense heat on thegions. The Dwarf Palm, again other. It is a flora, therefore, which could species of its kind left growing in Europe only have possessed the plains of England an inhabitant of southern France, reminds after the rigidity of the long-continued us of pre-glacial circumstances as much as glacial cold had given way to warmer conditions. In fact, it is a recent introduction, and there can be little doubt that its original home was Asia Minor. Most of our common English plants are now equally It would not be expected, especially as common in Japan. Our familiar flora from an evolutionist point of view, that seems to have originated in almost the plants whose species have a long ancestry same centre as Man himself! Possibly would grow in any great abundance over much of it may have accompanied his areas which have been subjected to succeswanderings, as we know it does attend the sive geological changes. We have already footsteps of the modern English emigrant. spoken of an arctic flora having first occuAny one looking over Dr. Hooker's recently pied the newly-emerged lands of the published, admirable "Student's Flora of "Drift" in Britain, and we return to the the British Islands," cannot but be aston-subject now for more detailed examinaished to see how geological barriers more tion. When the warmer changes ensued or less coincide with the geographical distribution of our commonest British plants. Of these barriers the great Sahara is one, and the northern flanks of the Himalayas another. We have seen that the former was sen during the period of the "drift," the only places remaining open to them which, of course, would forbid the northern migration of African species of plants. After its elevation, the burning sands of the desert formed a barrier quite as effective as a sea. Hence, as Mr. Andrew Murray has lucidly remarked, for all practical purposes in zoology and botany, we may regard that part of Africa, north of the Sahara, as a portion of Europe situated in Africa. It has a preponderance of European animals and plants, and was doubtless connected with Europe, by way of Gibraltar, before it was with Southern Africa.

which resulted in the present climature, the difference rendered the arctic flora unable to compete with the incoming Asiatic plants to which it was so favourable. Accordingly the former ceded the ground,

being the cold sides and summits of the higher mountains, where they would not be likely to be expelled by the newly introduced lowland and warmth-loving flora. Hence it is that we still find them growing on the margins of European glaciers, or on the tops of our English, Welsh, Irish, and Scotch mountains. On the Faulhorn, in the Canton of Berne, at nine thousand feet above the sea-level, there grow one hundred and thirty-two species of flowering plants, of which fifty-one are common to Lapland, and eleven to Spitzbergen. On the Engadine, a high valley in the The common flora we have spoken of as Canton des Grisons, there are found now occupying "merrie" England, is bo- eighty species of plants unknown to the tanically known as "Celtic." But, besides rest of Switzerland, but very common in this, we have even in this country an ad- the extreme north of Europe. Taking the mixture of other floras, whilst the conti-alpine flora of Switzerland as a whole, we nent of Europe is marked by a blended discover that out of a total number of association even more strongly. In this three hundred and sixty species, one hunrespect, their occupation is not unlike the dred and fifty-eight are common to Scanmixture of Latin and Teutonic races due dinavia and northern Europe generally. to the successive disturbances and invasions The relation of the European alpine flora during the earlier stages of European his- to that of the arctic regions may also be tory. For example, in the Pyrenees we obtained by reversing this comparison. have several species of plants still grow- Thus, out of six hundred and eighty-five ing which must have had a continuous flower-bearing plants found in Lapland, European descent from Miocene times. They have been adapted to the physical changes meantime at the expense, perhaps, of specific alteration. The Ramondia and Dioscorea really belong to Japan and China, and, as M. Martins has observed, to find them growing on the Pyrenees is as striking as if we found a family of Chinese or Japanese people living in the same re-planation!

one hundred and eight are also met with on the Swiss Alps. This extension of the arctic flora during the Glacial period is proved in a similar way on the Pyrenees, where we meet with sixty-eight species of plants which are common to Scandinavia. Thus do the very anomalies in natural history assist in the process of their own ex

Having rapidly glanced at the immedi- have been of so extensive a character, or ate influence of the later geological phe-of so long a duration. Whilst it lasted, nomena upon existing zoology and botany, however, Antarctic plants were driven let us next inquire whether the various northerly, just as in the northern hemphysical disturbances have been such as to isphere they were subsequently_forced enable us to investigate geographical dis- southerly by analogous agencies. Darwin tribution by the aid of certain general mentions that Australian plants are still principles? This is not altogether impos- found growing on the summits of the sible. For example, we may lay it down mountains of Borneo, and other islands of as a good rule, that islands which are sep- the Malayan Archipelago. They also exarated from adjoining continents by shal- tend along the highest parts of the Peninlow seas, have been insulated within a much sula of Malacca, and are thinly scattered, more modern period than those separated on the one hand over the mountainby deep seas. We find that the flora and ous regions of India, and on the other fauna of islands are related to those of the over similar tracts as far north as Jamainland in proportion to the depth of the pan. In some of the higher parts of intervening waters. Great Britain herself Equatorial regions we find Arctic and is a good illustration of the principle. She Antarctic plants in strange community, has no fauna peculiar to herself, except the the former predominating, perhaps on acwell known Red Grouse, and only one count of the greater proportion of land in plant, a species of orchid (Spiranthes). the northern hemisphere. We deduce All the rest are exactly like what we find from this occurrence an oscillation of exon the Continent. Our land and fresh- treme climates, or glacial epochs, in the water shells, fresh-water fish, &c., are iden- northern and southern halves of the globe tical, and as these could not have crossed alternately. Since the Antarctic glacial the salt sea, it is evident they must have period concluded, the Malayan Archipelaspread over England before she was sev-go has been formed by a breaking up of a ered from the European mainland. Deep prolongation of the Indian continent. Preseas are always indicative of longer periods of time to effect the depression, so that, if an island had been separated from Europe in Miocene times, its fauna and flora would still possess more or less of a Miocene facies. Such is the case with Madeira, the Azores, &c.; they were formed as volcanic islands early in the Tertiary period, and peopled by straggling birds, insects, plants, &c., from the adjacent mainland, as Sir C. Lyell has so clearly shown in the later editions of his "Principles." The absence of all mammalia, except bats, proves that this was the process (which Dr. Darwin has so clearly explained in his "Origin of Species ") by which such ancient volcanic islands were first stocked. Their areas have been considerably upheaved since then, and beds of volcanic ash are found in them, enclosing shells allied to those which lived on the mainland during the Miocene period. The existing land shells are lineal descendants of these. The plants of Madeira are also marked by similar belated features.

vious to this occurrence, there had been a similar extension of Australia in the opposite direction, so as to nearly join the former, and this had shared the same geographical fate, as the islands of New Guinea, &c., plainly show. The community of fauna and flora is such that we cannot be surprised native tradition should assert that Java, Sumatra, Bali, Lombok, &c., were all formerly united. The mountains of these islands form a continuous chain. The Asiatic animals and plants terminate at Bali, whilst the Australian commence at Lombok, thus showing that the tradition is zoologically wrong, if nearly geographically correct. In 1815, Mr. Earl pointed out that Java, Sumatra, and Borneo all stood on a plateau which was covered only by a shallow sea. The map indicates that this plateau is nowhere more that a hundred yards in depth. Mr. Wallace has last worked at this zoological problem, and with his usual keen perception of causation, has clearly shown how the fauna and flora of the Malayan islands are nearly Somewhere about the time that our allied to the Peninsula. Dr. Sclater was Norfolk and Suffolk "crags" were being the first to notice that the dividing line laid down, there were extensive geograph-between the Asiatic and Australian fauna ical and zoological changes taking place in must be drawn down the Straits of other parts of the world, besides the Macassar, and Mr. Wallace subsequently northern hemisphere. We have evidence of a similar cold epoch in the southern hemisphere to that which took place in the northern, although it does not seem to

showed that this line ought to be continued southwards through the Straits of Lombok. Looking at the islands which seem to act as a series of stepping-stones