sea, runs northwards and eastwards, and connects, as with a long bridge, the north of Iceland with the north of Newfoundland; 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

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 suffi cient 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

Y

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 daresay, 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 char