'IT is no recent discovery,' says an ingenious French writer of the last century, 'that there is no effect without a cause, and that often the smallest causes produce the greatest effects. Examine the situations of every people upon earth ; — they are founded on a train of occurrences seemingly without connexion, but all connected. In this immense machine all is wheel, pulley, cord, or spring. It is the same in physical nature. A wind blowing from the southern seas and the remotest parts of Africa brings with it a portion of the African atmosphere, which, falling in showers in the valleys of the Alps, fertilizes our lands. On the other hand, our north wind carries our vapours among the negroes: we do good to Guinea, and Guinea to us. The chain extends from one end of the universe to the other.' Waiving, however, for the present, the moral view of the question, I may be permitted to present my readers with an illustration of the physical one, — i.e., the dependence of the conditions of one country on the conditions on which some other and mayhap very distant country exists, — which may be new to some of them, and which the Frenchman just quoted could have little anticipated.

When in the island of Bute, to which I had gone on two several occasions in the course of a few weeks, in order to examine what are known to geologists as the Pleistocene deposits of the Kyles, my attention was directed to a deep


excavation which had just been opened for the construction of a gas tank in the middle of the town of Rothesay. It was rather more than twenty feet in depth, and passed through five different layers of soil. First, passing downwards, there occurred about eighteen inches of vegetable mould, and then about seven feet of a partially consolidated ferruginous gravel, which rested on about eighteen inches more of peat moss, — once evidently a surface soil, like the overlying one, though of a different character,  — abounding in what seemed to be the fragments of a rank underwood, and containing many hazel-nuts. Beneath this second soil there lay fully nine feet of finely stratified sea-sand; and under all, a bed of arenaceous clay, which the workmen penetrated to the depth of about two feet, but, as they had attained to the required depth of their excavation, did not pass through. And this bed of clay, at the depth of fully twenty feet from the surface, abounded in sea-shells, — not existing in the petrified condition, but, save that they had become somewhat porous and absorbent, in their original state. Not a few of them retained the thin brown epidermis, unchanged in colour; and the gaping and boring shells, whose nature it is to burrow in clay and sand, and which were present among them in two well-marked species, occupied, as shown by their position, the place in which they had lived and died. Now, of these ancient deep-lying shells, though a certain portion of them could be recognised as still British, there were proportionally not a few that no longer live within the British area; — in vain might the conchologist cast dredge for them in any sea that girdles the three kingdoms; and the whole, regarded as a group, differed from any other that exists in Europe in the present day. Ere, however, I pass on to decipher the record which they form, or translate into words the strange old prehistoric facts with which they are charged, let me briefly refer to the overlying deposits, and the successive periods of time which they seem to represent.


The upper layer of vegetable mould here fully exhausts the historic period. And yet the fine old town of Rothesay is not without its history. The ancient ivy-clad castle of the place is situated scarce a minute's walk from the excavation; the same stratum of vegetable mould lies around that forms the upper layer in the pit, furnishing rich footing to shrub and tree; and its green moat, deserted long since by the waters, was excavated of old in the ferruginous gravel. And yet, though compared with the age of the gravel-bed on which it stands, the date of its erection is as of yesterday: history fails to trace its origin: we only know that it was already an important stronghold in the days of Haco of Norway, one of whose captains besieged and took it, — that Robert III. of Scotland died broken-hearted within its walls, — and that it still furnishes with his second title the heir-apparent of the British throne. On many other parts of the coast, though apparently not here, this gravel-bed contains shells, all of which, unlike those of the arenaceous clay beneath, still live around our shores, and most of which occurred, ere the last upheaval of the land, as dead shells on the beaches of the old coast line. The old line itself; against which the sea seems to have stood for ages ere the final upheaval, is present here immediately behind the town, in an eminently characteristic form. Its precipices of rough conglomerate still exhibit the hollow lines, worn of old by the surf; and occupy such places in relation to the buildings below as prove that even the oldest erections of the town, with the first beginnings of the castle, were all raised on one of its wave-deserted beaches. But the annals of Rothesay, notwithstanding their respectable antiquity, or even such memorials of human origin in the neighbourhood as alto gether extend beyond the memory of history, advance comparatively but a little way towards the period of the old coast line and the last upheaval. When, in the times of Julius Caesar, Diodorus Siculus wrote his big gossiping


history, St. Michael's Mount, in Cornwall, was connected with the mainland at low water as it is now, — a fact good in evidence to show that since that age the respective levels of land and water have not altered in Britain. The old coast line must have been already upheaved when Cæsar landed in the island. And yet, though, as shown by its profound caves and deeply excavated hollows, the sea must have beaten against it during an immensely protracted period of depression, there existed a previous period of upheaval, represented by the layer of moss at the bottom of the gravel, when the land must have stood considerably higher over the sea-level than it does now. In many localities around the shores of Britain and Ireland, the moss-bed which so often underlies the bed of old coast gravel is found to run out under the sea to depths never laid bare by the tide; and yet at least as low as the sea ever falls, it is found bearing its stumps and roots of bushes and trees of existing species, that evidently occupy the place in which they had originally grown and decayed. these submerged mosses, as they are termed, occur along the sides of the Firths of Tay and Forth, and in at least one locality on the southern side of the Moray Firth; on the west coast they lie deep in lochs and bays; they occur on various parts of the coasts of Ire land; and off the shores of Erris and Tyrawly have furnished a basis for strange legends regarding an enchanted land, which once in every seven years raises its head above the water, green with forests and fields, but on which scarce any one has succeeded in landing. They occur also on the English shores, in one interesting instance in the immediate neighbourhood of that St. Michael's Mount, which, from the description of the Sicilian historian, furnishes a sort of negative measure of the period during which the gravel bed immediately over them was elevated. 'On the strand of Mount's Bay, midway between the piers of St. Michael's Mount and Penzance, on the 10th of January 1757,' says


Borlase, in his Natural History of Cornwall, 'the remains of a wood, which anciently must have covered a large tract of ground, appeared. The sands had been drawn off from the shore by a violent sea, and had left several places, twenty yards long and ten wide, washed bare, strewed with stones like a broken causeway, and wrought into hollows somewhat below the rest of the sands. This gave me an opportunity of examining the following parts of the ancient trees : — In the first pool part of the trunk appeared, and the whole course of the roots, eighteen feet long and twelve wide, were displayed in a horizontal position. The trunk at the fracture was ragged ; and beside the level range of the roots which lay round it was part of the body of the tree, just above where the roots divided. Of what kind it was there did not remain enough positively to determine. The roots were pierced plentifully by the teredo or auger worm. Thirty feet to the west we found the remains of another tree : the ramifications extended ten feet by six there was no stock in the middle ; it was therefore part of the under or bottom roots of the tree, pierced also by the teredo, and of the same texture as the first. Fifty feet to the north of the first tree we found part of a large oak; it was the body of a tree three feet in diameter; its top inclined to the east. We traced the body of this tree, as it lay shelving, the length of seven feet; but to what further depth the body reached we could not discern, because of the immediate influx of water as soon as we had made a pit for discovery. It was firmly rooted in earth six inches from the surface of the sand: not so fixed was the stock of a willow tree, with the bark on, one foot and a half in diameter, within two paces of the oak. The timber was changed into a ruddy colour; and hard by we found part of a hazel-branch, with its glossy bark on. The earth in all the tried places appeared to be a black, cold marsh, filled with fragments of leaves of the Juncus aquaticus maximus,


The place where I found the trees was three hundred yards below full sea-mark. The water is twelve feet deep upon them when the tide is in.' It will be seen from this description, — and it agrees with that of our submerged forests of the period generally, — that the trees which grew on this nether soil, when the level of the land stood con siderably higher than it does now, were exactly those of our present climate, — a fact borne specially out by the numerous hazel-nuts which the deposit almost everywhere contains. The hazel is one of the more delicate indigenous trees of the country. It was long ago remarked in Scotland by intelligent farmers of the old school, that 'a good nut year was always a good oat year;' and that 'as the nut filled the oat filled.' And now our philosophical botanists confirm the truthfulness of the observation embodied in these proverbial sayings, by selecting the hazel as the indigenous plant which most nearly resembles in its constitution the hardier cereals. It rises on our hill-sides to the height, but no higher, to which cultivation extends ; and where the hazel would fail to grow, checked by the severity of the climate, it would be in vain to attempt rearing the oat, or to expect any very considerable return from either rye or barley. The existence of hazel nuts, then, in this mossy stratum, is fraught with exactly the same sort of evidence regarding the climate of that period of upheaval which it represents, as that borne by the shells of the overlying gravel to the subsequent period when the sea stood against the old coast line. Equally during both periods our country possessed its present comparatively genial climate, —the finest enjoyed by any country in the world situated under the same lati tudinal lines. But the bed beneath gives evidence of an entirely different state of things.

Under the stratum of moss, as we have already said, there occurs in the Rothesay pit a thick bed of stratified sea-sand, and under the sand a bed of clay charged with


shells; and these shells exist no longer as a group in the British seas. Regarded as characters charged with the climatal history of the period that represents the stratum in which they occur, the following list, with the attached explanations, may be regarded as indicative of the meanings which they bear. We may mention, that the greater number of the specimens specified were collected in the pit after our first visit to it, by Mr. John Richmond of the Temperance Hotel, Rothesay, to whose intelligent guidance and direction the geologic traveller, desirous of cultivating an adequate acquaintance with the Pleistocene deposits of the island in the least possible time, would do well to commit himself.

species in stratum
species continued


Such were the shells found in the arenaceous clay-bed of the Rothesay pit, full twenty feet from the surface; and from where, in various other parts of the country, the same bed has been reached by excavations, or found cropping out along the shores, the list has been greatly increased. At Balnakaillie Bay, for instance, in the Kyles of Bute, where Mr. Smith of Jordanhill, — one of our highest authorities on the Pleistocene formation, — first detected the deposit, we found several specimens of the Pecten Islandicus, — a fine shell, which, though abundant on the coast of Labrador, has not been found living on those of Britain; with specimens of Panopea Norwegica, — a massive shell, of the same boreal character, recently, however, found on our coast; though such is its extreme rarity, that a conchol gical friend tells us he was lately offered a British specimen for sale, at the not very moderate price of two pounds ten shillings. Even in the instance in which the shells are not only British, but also not of extreme rarity, the proportions in which they occur in the beds are certainly exotic. Astarte elliptica, for instance, is by no means a common Astarte in the Scottish seas, nor is it at all known in those of England or Ireland; whereas in Greenland it is very abundant; and in those beds in which it is the prevailing Astarte, it is in the Greenlandic, not in the Scottish proportions, in which it occurs. In the same way Cyprina Islandica, though comparatively rare in the Firth of Clyde, is not rare in the Scottish seas generally; but it is in the seas of Iceland, as its name implies, that it attains to its fullest numerical development;


and in the Pleistocene beds of the Clyde it is in the Icelandic, not the Scottish proportions, that we find it. The same remark applies to Cardium Norwegica and Astarte compressa, with not a few others; and still more strongly to another Astarte, not rare in the Pleistocene deposits of at least Banffshire and Caithness, but so exceedingly rare as Scottish in the present age of the world, that the late Professor Edward Forbes, — indefatigable dredger as he was, — had to borrow from a friend the Scottish specimen which he figures in his great work. But though of such unfrequent occurrence in the Scottish seas, it is common in those of Nova Zembla and within the Arctic circle; and it is in the proportions in which it is developed in the high latitudes that we now find it in the Pleistocene beds of Scotland.

But how interpret so curious a fact as the occurrence in this country of beds of shells (evidently occupying the place in which they had lived and died) whose proper climatal habitat is now some ten or fifteen degrees further to the north? There is nothing more fixed than the nature of species. Art, within certain limits, exerts an acclimatizing power: Alpine plants may be found, for instance, living, if not flourishing, within the Botanic Gardens of Edinburgh, elevated scarce a hundred feet above the level of the sea; but every scientific gardener knows how extremely difficult it is to keep these alive in the too genial temperature of a situation greatly lower than the one natural to them; and that while inter-tropical plants may be easily maintained in existence through the judicious application of artificial heat, the sub-arctic or Alpine plants are ever and anon dying out. And never do they so change their natures as of themselvcs to propagate their kind downwards from the hill-tops to the plains. They on no occasion violate the climatal conditions imposed upon them by nature. It is so also with the animal world, and especially with shells. There are shells


reckoned British, so delicately sensible of cold, that their northern limit barely touches the southern shores of Britain. That fine bivalve Cytherea chione is one of these, never getting further north than Caernarvon Bay; Cardium rusticum, so graphically described by Mr. Kingsley in his Glaucus, under the style and title of Signor Tuberculato, is another, ranging southward to the Canaries, but barely impinging, in its northern limits, on the shores of Devon and Cornwall; and our splendid Haliotus, or ear-shell, H. tuberculata, though reckoned British by courtesy, does not even touch the British shores, but finds its northern limit at the Channel Islands. Nor are the northern shells more tolerant of warm than the southern ones of cold water. We have already referred to Astarte elhptica as finding its southern line of boundary on the Scottish coasts ; Pecten Niveus has not occurred to the south of the Firth of Clyde; and Trochus undulatus, though it ranges to Greenland, barely reaches our northern and western shores. Such and so nice is the dependence of shells on conditions of tempera ture, and such and so nice is their restriction to climatal areas. Nor could they have had a different nature in the past. How, then, could the cold Natica clausa and Trophon scalariforme of Spitzbergen and boreal America, and the Tellina proxima and Mya Uddevallensis of Greenland and the North Cape, have been at one time living denizens of the bay of Rothesay? Under what strange circumstances could whole scalps of the Pecten Islandicus have thriven in the Kyles of Bute, accompanied by groups of boreal Saxicava, that dug themselves houses in the stiff clay, and massive Panopea, that burrowed in the mud? The island of Bute is famous for now possessing perhaps the finest climate in Scotland: exotics blow in its gardens and shrubberies, that demand elsewhere the shelter of a green-house: and yet there was a time when, judging from the extreme boreal character of its shells, it pined under a severe and ungenial

[330 APPENDIX.] climate, in which even the hardier cereals could not have ripened. How account for a state of things so very unlike the present?

Questions in natural science cannot be resolved with all the certainty of questions in astronomical or mathematical science. Adams and Le Verrier could not only infer from the disturbances of Uranus the existence of a hitherto un known planet, but even indicate its place in the heavens. But though the varying climatal circumstances of our country, and of northern Europe generally, seem to have depended scarce less surely on the varying physical conditions of another country three thousand miles away, than the irregularities of the planet Uranus did upon the mass and position of the planet Neptune, we question whether any amount of skill, or intimacy of acquaintance with the phenomena, could have led to an a priori anticipation of the fact. We shall afterwards show, however, that the climate of northern Europe is mainly dependent on the conditions of Northern America; and that one certain change in its condition gave to our country the severe climate which obtained when Natica clausa and Tellina proxima lived in the bay of Rothesay; and that it is a result of another certain change in its condition, that the delicate fuschia now expands its purple bells in Bute on the soil by which great deep-lying accumulations of these subarctic shells are covered.

Let us first remark, that during the period of the boreal shells the land was greatly depressed. The subsequent depression, — that represented in the Rothesay excavation by the upper gravel-bed, — that which succeeded the age of the submerged mosses, — that during which the waves broke against the old coast line, — seems to have been restricted to a descent of some thirty, or at most forty, feet beneath the level which the land at present maintains; whereas the previous depression, — that represented by the bed of arenaceous clay and the boreal shells, — must have been a depression


of many hundred feet. No such inference, however, could be based on any of the Bute deposits which we have yet seen ; and yet we might safely conclude, even from them, that when these deep-sea shells lived where we now find them, the land must have sat comparatively low in the water. When scalps of Pecten Islandicus throve on the argillaceous bed cut open above tide-mark by the little stream which falls into Balnakaillie Bay, and noble Panopea burrowed in its stiff clay, Bute must have existed, not as one, but as three islands, separated from each other by ocean sounds occupying the three valleys by which it is still traversed from side to side. In the neighbouring mainland many a promontory and peninsula must have also existed as detached islands. The long promontory of Cantyre and Knapdale, traversed by open sounds at Tarbert and Crinan, must have formed two of these; the larger part of the shire of Dumbarton, cut off from the mainland by straits passing inwards through the valleys of the Leven and of Loch Long, must also have borne an insular character; Loch Lomond must have existed, not as a fresh water lake, but as an interior sea; and, in fine, the whole geography of the British islands must have been widely different from what it is now. There are other localities, however, in which, from the elevation of the boreal shell-bed over the present sea-level, we are justified in inferring that the depression of the land must have been much greater than that indicated by the beds of Bute. The same bed, and containing the same shells, was laid open in forming the Glasgow and Greenock Railway, a little to the west of Port-Glasgow, at an elevation of about fifty feet over the high-water line. It was detected at Airdrie, about fifteen miles inland, in the first instance, at a height of three hundred and fifty feet over the sea, and subsequently at the still more considerable height of five hundred and twenty-four feet. We ourselves have disinterred the same shells from


where they rested, evidently in situ, in Banffshire, — on the top, in one instance, of a giddy cliff; elevated two hundred and thirty feet over the beach, — in another, lying deep in the side of a valley once a long withdrawing firth, but now fully six miles from the sea, and raised about a hundred and fifty feet above it. In Caithness they have been detected by Mr. Robert Dick at the greatest heights to which the boulder-clay attains; they occur also at very considerable heights in the boulder-clay of the Isle of Man; and were found by Mr. Trimmer in the drift of Moel Tryfon, in North Wales, at the extraordinary elevation over the sea of fifteen hundred feet. When the boreal shells at Airdrie lived, Scotland must have existed as a wintry archipelago, separated into three groups by the oceanic sounds of the great Caledonian Valley, and of the low flat valley, now traversed by the Union Canal, which extends between the Firths of Forth and Clyde. And when the shells of Moel Tryfon lived, only the higher parts of the Highlands of Scotland, and of the Cheviot and Lammermuir groups, could have had their heads elevated over the wintry ice-laden sea of the Pleistocene agents. There are grounds for holding that the period, though one geologically, was of vast extent, — that the degree of submergence was greater at one time and less at another; or, more strictly speaking, that the commence ment of the period was one of gradual depression in the British area, — that about its middle term all was submerged, save the hill-tops and higher table-lands, — and that our country then began gradually to rise, until, about the close of the wintry eon, its level was mayhap scarce a hundred feet lower than it is at present. But though comparatively greater and less at different times, there seems to have been no time during the period, in which the depression was not absolutely great.

Let us next remark, as very important to our argument, that not only was the period one of depression in the British


area, but also very extensively in the northern hemisphere generally. The shell-beds of Uddevalla, — identical in the character and species of their organisms with those of the Clyde, — are elevated two hundred feet above the neighbouring Cattegat; and in Russia Sir Roderick Murchison detected similar beds in the valley of the Dwina, lying nearly two hundred miles south-east of Archangel, and at least a hundred and fifty feet over the level of the White Sea. It is not uninteresting to mark, in the list of shells given by Sir Roderick in his great work on Russia, and which were the product, he states, of not more than two hours' exploration among these far inland beds, exactly the names of the same species that occurred in the Rothesay excavation, or may be found in the Pleistocene deposits of the Kyles. We recognise as the prevailing forms, Natica clausa, Pecten Islandicus, Astarte elliptica, Astarte compressa, Mya truncata in both its boreal and more ordinary varieties, and Tcllina proxima, with many others. The inscriptions borne by the Pleistocene of both Sweden and Russia are formed of the same character as those exhibited by the Pleistocene of our own country, and tell exactly the same story. But it is of still more importance to our argument, that the Pleistocene of America is also inscribed with similar characters, and is coupled with similar evidence. Shell-beds identical in their contents with those of the Clyde, Uddevalla, and the valley of the Dwina, have been detected in the neighbourhood of Quebec, at the height of two hundred feet over the Atlantic, and traced onwards by Mr. Logan, the accomplished State-geologist for the Canadas, to the height of four hundred and sixty feet. And in these American beds, separated from those of the Dwina by a hundred and twenty degrees of longitude, Pecten Islandicus, Natica clausa, Mya truncata, Saxicava rugosa, and Tellina proxima, are the prevailing forms. How very wide the geographic area which these shells must have possessed of old! A 


depression of the North American Continent to the amount of but four hundred and sixty feet would greatly affect its contour. It would cut it off from Southern America — the highest point over which the Panama Railway passed was but two hundred and fifty feet over the level of the sea — and unite the Atlantic and Pacific Oceans by a broad channel, more than thiity fathoms in depth. But from various other appearances the American geologists claim for their country a much greater depression than even that of Moel Tryfon in Wales. It must have been depressed at least two thousand feet, and a wide sea must have passed through the valley of the Mississippi into what is now the Lake district, and from thence into Hudson's Bay and the Arctic Seas. And now, let the reader mark the probable effects on the climate of Northern Europe generally, and on that of Britain in particular, of so extensive a submergence of the American Continent.

No other countries in the world situated under the same lines of latitude enjoy so genial a climate as that enjoyed by the British islands in the present day. The bleak coasts of Labrador lie in the same parallels as those of Britain and Ireland; St. John's, in Newfoundland, is situated considerably to the south of Torquay in Devon; and Cape Farewell in Greenland, to the south of Lerwick, the capital of the Shetland Islands. But how very different the climate of these bleak occidental lands, from that which renders Great Britain one of the first of agricultural countries! At Nain, in Labrador, situated in the same latitude as Edinburgh, the ground-frost at the depth of a few feet from the surface never thaws, but forms an ungenial rock-like subsoil, against which the labourer breaks his tool, and over which the cereals fail to ripen. From the northern coasts of Newfoundland, though lying under the same latitudinal lines as the extreme south of England, there forms in winter a thick cake of ice, which, binding up the stormy

sea, runs northwards and eastwards, and connects, as with a long bridge, the north of Iceland with the north of New foundland; thus constituting a natural isothermal line, which shows that the European island has a not severer climate than the American one, though it lies more than ten degrees further to the north. And be it remembered that, did climate depend exclusively on a country's latitudinal position on the map, and its distance from the sun, it is the climate of Northern America that would be deemed the ordinary and proper climate, and that of Northern Europe the extraordinary and exceptional one. Great Britain and Ireland owe the genial, equable warmth that ripens year after year their luxuriant crops, and renders their winters so mild that the sea never freezes around their shores, not at least directly, to the distant sun. Like apartments heated by pipes of steam or hot water, or green-houses heated by flues, they derive their warmth from a heating agent laterally applied: they are heated by warm water. The great Gulf Stream, which, issuing from the Straits of Florida, strikes diagonally across the Atlantic, and, impinging on our coasts, casts upon them not unfrequently the productions of the West Indies, and always a considerable portion of the warmth of the West Indies, is generally recognised as the heating agent which gives to our country a climate so much more mild and genial than that of any other country whatever similarly situated. Wherever its influence is felt, — and it extends as far north as the southern shores of Iceland, Nova Zembla, and the North Cape, — the sea in winter tells of its meliorating effects by never freezing: it remains open, like those portions of a reservoir or canal into which the heated water of a steam-boiler is supposed to escape. In some seasons, — an effect of unknown causes,  — the Gulf Stream impinges more strongly against our coasts than at others: it did so in 1775, when Benjamin Franklin made his recorded observations upon it, — the first

[APPENDIX.  336]

of any value which we possess; and again during the three mild winters that immediately preceded the last severe one, — that of 1855, — and which owed their mildness apparently to that very circumstance. It was found during the latter seasons that the temperature of the sea around our western coasts rose from one and a half to two degrees above its ordinary average; and it must be remembered how, during these seasons, every partial frost that set in at once yielded to a thaw whenever a puff of wind from the west carried into the atmosphere the caloric of the water over which it swept. The amount of heat discharged into the Atlantic by this great ocean-current is enormous. 'A simple calculation,' says Lieutenant Maury, 'will show that the quantity of heat discharged over the Atlantic from the waters of the Gulf Stream in a winter day would be sufficient to raise the whole column of atmosphere that rests upon France and the British Islands from the freezing point to summer heat. It is the influence of this stream upon climate,' he adds, 'that makes Erin the Emerald Isle of the sea, and clothes the shore of Albion with evergreen robes; while in the same latitude, on the other side, the shores of Labrador are fast bound in fetters of ice.'

Now, a depression beneath the sea of the North American continent would have the effect of depriving northern Europe of the benefits of this great heating current. Its origin has been traced to various causes, — some of them very inadequate ones. It has been said, for instance, that it is but a sort of oceanic prolongation of the Mississippi. It has been demonstrated, however, that it discharges through the Straits of Florida about a thousand times more water than the Mississippi does at its mouth; and yet, even were the case otherwise, and the view correct, any great depression of North America would cut off the Mississippi from among the list of great rivers, by converting the valley which it occupies into a sea, and would thus terminate the


existence of the Gulf Stream. The stream has, however, a very different and more adequate origin, but one which the depression of the North American continent would equally affect. It is a reaction on the great Drift Current. If the reader take a cup or basin filled with water, and blow strongly across the surface of the fluid, two distinct currents will be generated, — a drift current, which, flowing in the direction of his breath, will impinge against the opposite side of the vessel, — and a reactionary current, which, passing along its sides, will return towards himself And nothing can be more obvious than the principle on which this occurs. The drift current, more immediately generated by his breath, heaps up the water against the side of the vessel on which it impinges; and this heaped-up water must of course inevitably seek to return to the other side, in order to restore the deranged equilibrium of level. Now, the Northern Atlantic, — the Atlantic to the north of the equator, — displays on an immense scale exactly the phenomena exhibited by this simple experiment of the cup or basin. The breath of the trade-winds, ever blowing upon it from the east and north-east, in that broad belt which lies between the tenth and the twenty-sixth degrees of north latitude, forms a great drift current, which, impinging on and heaping up the waters against the South American coast,  — the opposite side of the cup or basin, — flows northwards into the Carribbean Sea and Mexican Gulf; and, issuing from the Straits of Florida in the character of the reactionary Gulf Stream, strikes diagonally across the Atlantic full on Northern Europe. But the existence of this reactionary stream is not merely and exclusively a consequence of the existence of the Drift Current: it is also equally a consequence of the existence of an American continent. Save for the side of the basin or cup opposite to that whence the breath comes, the water, instead of returning in a reactionary current, would flow over. Such a wide breach


in the sides of the cup along the Isthmus of Panama, for instance, as a depression of but four hundred and sixty feet would secure, would permit the Drift Current to flow into the Pacific. Such a wide breach in the sides of the cup along the Valley of the Mississippi as a depression equal to that indicated by the shells of Moel Tryfon would secure, would permit the reactionary Gulf Stream, though already formed, to escape, along what is now the lake district of America, into Hudson's Bay. In either case the Gulf Stream would be lost to Northern Europe; and the British Islands, robbed of the Gulf Stream, would possess merely the climate proper to their latitudinal position on the map; — they would possess such a climate as that of Labrador, where, beneath seas frozen over every winter many miles from the shore, exactly the same shells now live as may be found, in the sub-fossil state, in the Kyles of Bute, or underlying the pleasant town of Rothesay. A submergence of the North American continent would give to Britain and Ireland, with the countries of Northern Europe generally, what they all seem to have possessed during the protracted ages of the Pleistocene era, — a glacial climate.

If our conclusions be just, — and we see not on what grounds they are to be avoided, — our readers will, we dare-say, agree with us that it would not be easy to produce a more striking illustration of the influences which are at times exerted by the conditions of one country on those of another. Our brethren of the United States are occasionally not a little jealous of the mother country; but we suspect all of them do not know how completely they could ruin her could they but succeed in keeping their great Gulf Stream to themselves. It might be unwise, however, to urge matters quite so far, lest they should provoke us, in turn, to demand back again the large brains and high-mettled blood which we have most certainly given them. Such of our readers as occasionally enjoy a summer vacation on the west coast


might find it no dull or useless employment to begin reading for themselves the shell inscriptions borne by the Pleistocene deposits. It would at once form an excellent exercise in Conchology and a first lesson in Geology, which, from the interest it excited, would scarce fail to lead on to others. With their eyes educated to the work too, they would find, we doubt not, the beds in many a new locality in which they had not been detected before; and enjoy the same sort of pleasure in falling upon a fresh deposit, as that enjoyed by an Egyptian or Assyrian antiquary when he discovers a catacomb of unrolled mummies never before laid open, or a series of sculptures or of inscriptions in the cuneiform character, unseen since the days of Semiramis or Sennacherib. We ourselves once enjoyed such a pleasure at Fairlie; — we laid open a noble bed, previously unknown, about a quarter of a mile to the north of the village; and from amid great scalps of Pecten Islandicus, roughened on their upper valves by huge Balonidæ, and from beside thick-lying groups of Cypinidæ, we disinterred many a curious boreal shell, — great massive Panopea, graceful Veneridea, the Greenland Mya, and the Tellina of the North Cape; and beneath all we detected grooved and dressed rock-surfaces, that bore their significant markings as freshly as if the grating ice had passed over them but yesterday. We would specially call the explorer's attention to the corroborative evidence borne by appearances of mechanical origin such as these to the mute testimony of the shells. We have already incidentally referred to the interesting deposits of Balnakaillie Bay. A stream falls into the sea at its upper extremity, and exhibits, in the section which it supplies, a bed charged with the old boreal shells, from where it creeps out along the beach, till where we lose it in the interior, far above the reach of the tide. As it passes inwards, we find the old coast line deposits resting over it; in one place assuming the ordinary character


of a stratified sand and gravel; in another existing as a partially consolidated conglomerate; while immediately beneath it, on the north side of the stream, the rock appears strongly marked by the old glacial dressings. The mechanical and zoologic evidences of the existence of a period of extreme cold thus lying side by side may be studied together. But the district has its many such appearances. Not a few of the hills bear, in their rounded protuberances and smoothed and channelled hollows, evidence of the ice-agent that wasted them of old; and in the valley of the Gareloch, only a few miles distant, Mr. Charles Maclaren found unequivocal traces of an ancient glacier.

But the collateral evidences would lead us into a field quite as wide as that into which we have made our brief excursion, and are now preparing to leave. The following interesting extract from Mr. Kingsley's Glaucus, with which we conclude, may at once show how rightly to read these, and what very amusing reading they form. It is thus we find Mr. Kingsley accounting, in light and graceful dialogue, for the formation of a profoundly deep lochan of limited area, that opens its blue eye to the heavens amid the rough wilderness of rocks and hills that encircle the gigantic Snowdon.

'You see the lake is nearly circular: on the side where we stand the pebbly beach is not six feet above the water, and slopes away steeply into the valley behind us, while before us it shelves gradually into the lake; forty yards out, as you know, there is not ten feet water, and then a steep bank, the edge whereof we and the big trout know well, sinks suddenly to unknown depths. On the opposite side, that vast flat-topped wall of rock towers up shoreless into the sky seven hundred feet perpendicular: the deepest water of all, we know, is at its very foot. Right and left two shoulders of down slope into the lake. Now turn round, and look down the gorge. Remark that the pebble


bank on which we stand reaches some fifty yards down ward: you see the loose stones peeping out everywhere. We may fairly suppose that we stand on a dam of loose stones, a hundred feet deep.

'But why loose stones? and if so, what matter and what wonder? There are rocks cropping out everywhere down the hill-side.

'Because, if you will take up one of these stones, and crack it across, you will see that it is not of the same stuff as those said rocks. Step into the next field and see. That rock is the common Snowdon slate which we see everywhere. The two shoulders of down right and left are slate too; you can see that at a glance. But the stones of the pebble bank are a close-grained yellow-spotted Syenite; and where, — where on earth did these Syenite pebbles come from? Let us walk round to the cliff on the opposite side and see.

'Now mark. Between the cliff-foot and the sloping down is a crack, ending in a gully: the nearer side is of slate, and the further side the cliff itself. Why, the whole cliff is composed of the very same stone as the pebble ridge.

'Now, my good friend, how did these pebbles get three hundred yards across the lake? Hundreds of tons, some of them three feet long, — who carried them across? The old Cimbri were not likely to amuse themselves by making such a breakwater up here in No-man's-land, two thousand feet above the sea; but somebody or something must have carried them, for stones do not fly, nor swim neither.

'Let our hope of a solution be in John Jones, who carried up the coracle. Hail him,, and ask what is on the top of that cliff. So ? — " Plains and bogs, and another linn." Very good. Now, does it not strike you that the whole cliff has a remarkably smooth and plastered look, like a hare's run up an earth bank? And do you see that it is polished thus only over the lake? that as soon as the cliff abuts on the

[342 APPEND1X.]

downs right and left, it forms pinnacles, caves, broken angular boulders? Syenite usually does so in our damp climate, from the weathering effect of frost and rain; why has it not done so over the lake? On that part something (giants perhaps) has been scrambling up and down on a very large scale, and so rubbed off every corner which was inclined to come away, till the solid core of the rock was bared. And may not these mysterious giants have had a hand in carrying the stones across the lake? . . . Really I am not altogether jesting. Think a while, what agent could possibly have produced either one or both of these effects?

'There is but one; and that, if you have been an Alpine traveller, much more if you have been a chamois-hunter, you have seen many a time (whether you knew it or not) at the very same work.

'Ice! Yes; ice. Hrymin the frost-giant, and no one else. And if you look at the facts, you will see how ice may have done it. Our friend John Jones' report of plains and bogs, and a lake above, makes it quite possible that in the ice-age (glacial epoch, as the big-word-mongers call it), there was above that cliff a great neve or snow-field, such as you have seen often in the Alps at the head of each glacier. Over the face of this cliff; a glacier had crawled down from that neve, polishing the face of the rock in its descent; but the snow, having no large and deep outlet, has not slid down in a sufficient stream to reach the vale below, and form a glacier of the first order, and has therefore stopped short on the other side of the lake, as a glacier of the second order, which ends in an ice-cliffhanging high up on the mountain side, and kept from further progress by daily melting. If you have ever gone up the Mer-de-Glace to the Tacul, you saw a magnificent specimen of the sort on your right hand, just opposite the Tacul, in the Glacier de Tre'laporte, which comes down from the Aiguille de Charmoz.


'This explains our pebble ridge. The stones which the glacier rubbed off the cliff beneath it, it carried forwards slowly but surely, till they saw the light again in the face of the ice-cliff; and dropped out of it under the melting of the summer sun, to form a huge dam across the ravine; till, the "ice-age" past, a more genial climate succeeded, and neve and glacier melted away; but the "moraine" of stones did not, and remain to this day, the dam which keeps up the waters of the lake.

'There is my explanation. If you can find a better, do; but remember always that it must include an answer to, — How did the stones get across the lake?'