J. W. Dawson has extended this conclusion as to the arctic origin of the Tertiary floras to those of more ancient periods, and concludes that the Silurian, Devonian, and Carboniferous floras all entered the North American continent from the northeast, and that within the arctic circle was the great nursery in which the successive vegetations, from the oldest to the most recent, had their origin.

ANCIENT ARCTIC CLIMATE.

Dawson supposes that the subsequent change in climate in these northern regions was geographical rather than cosmical, and that the arctic climate at the sea-level, as long taught by the present writer, never attained the point of glaciation until the end of the Tertiary time.

In like manner, J. F.Campbell, abandoning his former views of a great ice-cap, now concludes that no geological record exists of any abnormal glacial periods colder than the world's climate of to-day. Geographical changes affecting the relations of sea and land, and elevating portions of the earth's surface into regions of the atmosphere where perpetual frost prevails, will, according to him, account for all the phenomena.

SUPPOSED DISPLACEMENT OF THE EARTH'S AXIS.

J. W. Dawson calls attention to the well-known fact that not only the movement of successive floras in this continent, but the directions of the great accumulations of sediment throughout all these periods, as well as the great lines of plication of the strata, which depend upon these, coincide with the direction of the polar currents of to-day, and remarks that all these facts go to refute the notion, which has lately been resuscitated, of a change in the position of the earth's axis of rotation-a view which, however conceivable to the astronomer and the physicist, cannot be admitted by the geologist, who sees, in the facts already set forth, the evidence that no considerable change of that kind can have taken place since the beginning of Paleozoic time. Polar currents seem to have been in all ages the potent agents in transporting the débris of older rocks towards the equator; while, on the other hand, as remarked by Dawson, the great organic limestones, which represent the contemporaneous food-bearing warm currents from equatorial regions, were deposited

in the plateaus and in the bays of the Eozoic and Paleozoic lands. See in this connection the same argument against a change of axis stated in the Record for 1876 (page cii).

AN ANCIENT ATLANTIC CONTINENT.

The results of soundings over the bed of the Atlantic have made clear the existence through the middle of the ocean, extending from north to south, of a sunken ridge, often less than 1000 fathoms from the surface, while on either side the water has a depth of from 3000 to more than 3450 fathoms; so that the elevation of the ocean's bottom required to make these depths dry land would bring up between them a mountain-range from 9000 to 15,000 feet in height. The higher points of this sunken ridge now form the islands of the Azores-St. Paul's, Ascension, and Tristan d'Acunha. This discovery was, in a manner, anticipated in 1860 by Unger, who, from his studies of the Tertiary flora of Europe and America, was led to imagine a land connecting the two regions, over which the plants of North America had passed eastward. This, he supposed, might be the vanished Atlantis of which Plato has preserved the tradition.

Other reasons have led geological observers to conclude that great areas of land existed in the Atlantic region in Paleozoic time; and the present writer, in 1872, urged the existence of a Paleozoic Atlantis, from the ruins of which had been derived the enormous volumes of material which make up the uncrystalline rocks of Eastern North America. The Paleozoic sediments of these regions, many miles in thickness, must, as Hall and H. D. Rogers long since pointed out, have been derived from the waste of great areas of elevated land lying to the eastward. Clarence King has recently brought forward this doctrine in a forcible manner, and has described Palæ-Atlantis as a land-area of continental magnitude, from which vast quantities of sediment were brought down by rivers and poured into the Palæ-American ocean, upon the subsiding bottom of which were built up the thick Paleozoic formations which stretch throughout Eastern North America. He also claims the existence of a corresponding Pacific continental area, which he names Palæ-Pacifis. The lower Paleozoic rocks of Great Britain, when compared with those of Scandinavia and Russia, show a diminution in thickness in

going eastward not less remarkable than that observed in the opposite direction in the strata of the same age in North America.

EUROPE AND ASIA IN THE GLACIAL PERIOD.

Belt has put forward a theory with regard to the glacial period in Northern Europe. He supposes, with Croll, that the North Sea between Scandinavia and Scotland was at one time filled with ice, so that (Great Britain being then continuous with the continent) the German Ocean was blocked up to the north, and formed a great lake, the waters of which found an outlet to the southwest, and gradually cut through the Straits of Dover. From the waters of this lake, which gradually became fresh, were deposited the clays of Southeastern England. The ice, as it advanced southward, reached the coast of Norfolk, and not only denuded and disturbed these clays, but, according to Belt, uplifted both the Cretaceous and Neocomian, and even forced the boulderclay beneath their inclined strata.

THE LOESS OF CENTRAL EUROPE.

The alluvial deposit known as the loess, which attains a height of 900 feet above the sea on the Rhine and 1300 feet on the Danube, is, in the opinion of Belt, of glacial origin, and, in fact, the equivalent of the northern glacial drift, which passes gradually into the loess. The conditions which permitted the deposition of these were, according to Belt, brought about, not by a subsidence of the land, but by a great glacier which occupied the bed of the Atlantic to a height of about 1700 feet above the sea, damming back the rivers which drain the continent, and converting this into a vast lake, which was filled with icebergs. He has since extended this hypothesis, and supposes that another great glacier extended down the North Pacific, arresting also the drainage of Asia.

After the Miocene age, the Aralo-Caspian area was cut off from its connection with the Mediterranean, when the northern basin grew fresh, and discharged its waters to the north, until, by the accumulation of ice both in the Atlantic and the Pacific, the drainage of this region was checked, and there was formed a great lake, into which came the icebergs

from the north, depositing boulder-drift in the north and clay in the south of Russia. This state of things was finally put an end to by the cutting of the channel of the Bosphorus, through which the waters found an exit southward.

GLACIAL PHENOMENA AROUND LAKE ONTARIO.

George J. Hinde has studied the Post-tertiary deposits near Toronto, which throw new light on the geology of that region. The eroded Loraine or Cincinnati shales are here overlaid by a considerable thickness of boulder-clay, including a veritable pavement of striated boulders. Overlying this are thinly stratified sands and clays, which have a maximum thickness of 140 feet, and contain remains of plants, chiefly mosses, with some mollusks and crustacea, showing this to have been a lacustrine deposit. These are conformably overlaid by about forty feet of sand. Subsequent erosion has cut in one case a valley in these stratified deposits to a depth of more than one hundred feet, and the clay beds in the vicinity of the erosion are often curiously contorted. Over this is a second boulder-clay, filling up the depressions, and covering over the higher portions to a depth of seventy feet. This is, in its turn, overlaid by a second series of stratified clays without observed organic remains, upon which appears in one place a stratum of about thirty feet of what is regarded as a third deposit of boulder-clay, succeeded by stratified sands and gravels.

To correlate these deposits, studied by Mr. Hinde, with the clays of the regions farther south and west will require further study. The evidence of more than one period of erosion was many years since pointed out by the present writer, who showed the existence of a vast rock-basin cut out of the Devonian strata, and filled up with clays, out of which latter deposit the basin of Lake St. Clair and that of the southwestern half of Lake Erie were subsequently eroded, the stratified clays on the shores of the latter reaching to depths far below the bottom of the lake.

GLACIAL PHENOMENA IN LABRADOR.

Henry Youle Hind has studied the joint action on the Labrador coast of the polar current and of the sheets of ice called by the fishermen pans (i. e., panes). These are great

tables or plates, varying from five to ten and twelve feet in thickness, and from a few square yards to many acres in extent, which are formed by the breaking-up of the coast and bay-ice in the month of June. These sheets, when pressed to the coast by winds and urged by the unfailing arctic current from the northwest, rise over the low-lying shores and islands, removing every obstacle in their way, grinding and polishing the surface, and rounding into boulders the masses broken or torn from the cleavable rocks in their course. This process, with some interruption from winds, goes on for a month or six weeks every year, and the bottom of the sea, to the depth of twelve feet or more, exhibits white smooth surfaces, which have been thus ground and planed by the action.

Pan-ice, according to this observer, is now "exerting an abrading action over a vast coastal and submarine area throughout the shallow seas that fringe Labrador. In a word, it is doing before our eyes, over a coast-line many hundred miles in length, what has been done in earlier times over a vast area of the North American continent, according as fresh surfaces, by a rise or subsidence of the land, were brought under the influence of pan-ice aided by an arctic current. The evidence of a gradual uplifting of this coast during the continuation of this process is seen in the smooth worn surfaces up to more than 600 feet above the present sea-level. The material pushed to and fro along a shallow sea-bottom by this action of ice must accumulate in submarine depressions in the form of boulder-clay, which, however, in a rising area, would, except where locally protected in deep valleys, be remodelled by the action of the waves." To such an action he attributes the boulder-clays of Nova Scotia. Similar views of the action of shore-ice are urged by J. Milne, who, from his studies in Newfoundland and Labrador, as well as in Finland, concludes that many of the phenomena which some have referred to the action of an ice-cap, or a great extension of land-ice, are due to the action of coast-ice on an oscillating and especially on a rising submarine area. On the other hand, the phenomena described on the shores of Lake Ontario are strongly urged, by its advocates, in favor of the hypothesis of subaerial glaciation.