Leda) clay of eastern Canada; and Dr. Dawson has identified these with the Marine clays of Maine. The latter are found in all the valleys near the sea level both in that State and New Brunswick, but have not been traced to any considerable height above the sea. All these clays in New England and the eastern Provinces of Canada are of marine origin, but the Erie clays were probably deposited in fresh-water. In New England as well as Acadia there are masses of superficial materials which underlie these marine clays, and should therefore be older than the Erie clay. Dr. Newberry does not appear to recognize them in the region underlaid by this deposit. These older masses of loose materials present in New Brunswick all the features of unmodified drift, and reach to the tops of the highest hills in the southern counties of that Province. While all the other surface deposits in their arrangement betray to a greater or less degree the sorting power of water, this alone, so far as has been ascertained, is unstratified throughout. It consists of clay and sand promiscuously mingled. These finer materials enclose numberless striated stones and angular fragments having no definite arrangement in the mass, but irregularly distributed throughout it. For a height of two hundred feet above the sea, the Boulder clay has been greatly modified by the action of waves and currents during a period of slow subsidence, and in the valleys it is covered with beds of fine clay.

THE CONTINENTAL GLACIER.-Two theories have been advanced to explain the phenomena of drift, namely that which attributes them to the action of icebergs and ocean currents, and that wherein glacier action plays an important part. If the latter be ignored, it would seem no easy matter to account for some of the characteristics of the Drift in this region, such as the smoothing and furrowing of low-lying ledges under the lee of continuous hill ranges; the striation of the undersides of ledges; the transverse grooving of narrow valleys, etc. Since the topography of the region is not favourable to the formation of local glaciers, there being no high mountains in or near it, if the Acadian drift resulted from glacier erosion, the glacier would have been a widespread sheet of ice, covering the whole surface of the country, similar to those of the Antarctic continent, or of Greenland. Rivers of ice flow down to the sea-side from the wide fields of compacted snow which covers a large part of the country last named; large masses of these frozen streams are detached at the coast, and

floating southward on the Arctic current along the Atlantic coast, add the distributing power of bergs to that of glaciers.

The degree of cold necessary to bring such an icy covering down to the latitude of St. John (N.B.) does not seem more improbable than the contrary amount of heat which in the preceding age enabled palms to flourish in New England and perhaps in Acadia also.

In an article on the Arctic and western plants of this region, which I had the honour to read before you two years ago, it was shewn that the mean annual summer temperature of this city was nearly two degrees lower than that of Thunder Bay on the north. shore of Lake Superior. Undoubted indications of the former existence of glaciers on the north shore of that lake were seen by Prof. L. Agassiz; and Sir. W. E. Logan also alludes to similar instances observed by him. He considers glaciers to have been one of the chief agents in excavating the great lake basins.* If, during the glacial period the isothermal lines of the continent moved southward at an equal ratio in the east and west, we might readily admit that glaciers existed here as well as on the great lakes of the St. Lawrence basin.

Rigid as ice under ordinary circumstances appears, it is now well known that it possesses a certain amount of plasticity. Rendu, Agassiz, Forbes and others, who have carefully studied the Alpine glaciers, have clearly demonstrated the existence of this property in glacial ice. It enables the ice to accommodate itself to the inequalities of the surface on which it rests, and to slide down the ravines and narrow valleys of the mountain side, bearing along with it trains of boulders and loose masses of stones and earth. The rate at which glaciers move is very variable, being governed by the slope of their beds and the obstacles met by the moving ice, but it may be roughly set down at from nine inches to a yard daily for the majority of the Swiss glaciers. Glacier motion is analogous to that of rivers. Where the sheet of ice is broad and the slope moderate, the motion is slow, but where the ice passes through narrow gorges the rate of motion is accelerated. Another point of resemblance to rivers is the motion acquired in passing around curves, the strength of the current being thrown-both in the case of glaciers and rivers-on the outside of the curve. The momentum of ice in motion causes it

• Report of Progress, Canadian Survey, 1863, page 889.

to press heavily on projecting ledges of rock and exposed shoulders of hills. Hence the rocks along the sides of glaciers are striated and smoothed in a manner similar to that of the rock surfaces in New England and Canada.

Extensive as Alpine glaciers are now, they are insignificant compared with what they are shown to have been in former times, by the moraines and boulders which they have left in the low lands, both north and south of the Alps. They are known to have extended fifty miles or more downward from the mountain tops into the valley of the Po. On the north side of the Alps existed a great glacier filling the valley of the Rhone, and extending in the direction of Neufchatel. This great sheet of ice is asserted to have been from 4000 to 5000 feet in thickness, and to have had a slope from the summit of Mont Blanc to the Juras of very nearly one degree. It is also at a height of about 5000 feet that the limit of glacial striation is reached in the New England hills. Mountains which have an elevation of 4000 feet have striæ across the summit, but neither the tops of the White Hill nor (according to Prof. C. H. Hitchcock) that of Mount K'tahdin, in Maine-5300 feet high-are striated. Assuming that Acadia was, during the drift period, covered by a great glacial sheet, such as now exists in Greenland, and formerly filled the valleys of Switzerland, let us endeavour to get some idea of its probable form and depth. In doing so we should bear its physical features in mind. New Brunswick, as a whole, is a country of plains, rolling uplands, and low hill ranges. It has a group of eminences near its northern border, of which only one is known to be more than 2500 feet above the sea. Another knot of hills exist near the Chepetrieticook Lakes, on the western border; and a series of overlapping ridges, none of which much exceed 1000 feet in elevation, along the southern coast. There is not such a slope in the surface of the land as that which in New England may have given momentum to the glacial mass. The general course of the drift striæ on the higher elevations in the central and northern part of New Brunswick, is said to vary from south to two degrees east of south. This is also the course of the grooves obser ved at the higher levels in the Southern Hills, and it may be regarded as the probable course of the glacier in the eastern part of New Brunswick at the time of its fullest development. Such being the form and motion of this continental mass of ice, a portion would have crossed the Bay Chaleur at Gaspé, traversed the

plain of eastern New Brunswick, and surmounted the more easterly ridges along the north shore of the Bay of Fundy, there being meridinal grooves on these ridges to the height of 1000 feet. Hills of this altitude must have been surmounted by a continental glacier such as we have supposed, else its motion would have been arrested at their base. But as an extensive plain stretches away to the north from the base of these hills and passes beneath the Gulf of St. Lawrence, a slope like that of the great Swiss glacier above mentioned, could not have carried the ice over the summit of this range, unless the mass of ice were two and a-half miles thick on the depression now occupied by the Bay Chaleur.

It is evident, however, from several considerations that such a mass of ice could not have existed in Acadia. A glacier of this depth would have been double the height of Mount Washington, the highest peak in Eastern North America, upon which there are no striæ at a greater height than 5000 feet. And the existing continental glacier of Greenland to which the supposed Acadian glacier has been compared, averages only about 2000 feet in thickness. The non-existence of a glacial mass exceeding this thickness may also be inferred upon physical grounds-the internal heat of the globe alone, would prevent it from attaining great thickness. From the comparison of observations carefully made in different parts of Europe it was inferred some years since that terrestrial heat increased in descending toward the centre of the earth at the rate of one degree Fahr. for every sixty feet of descent; but it was suspected that the observed rate of increase in temperature was materially effected in the case of mines (where the observations were chiefly made) by heat evolved during the decomposition of sulphurets of the metals, and in the case of artesian well, by warm waters rising from great depths through fissures in the earth's crust. A means of correcting these observations has been afforded by the Mount Cenis tunnel beneath the Alps. This artificial passage connecting Italy and Savoy is between seven and eight miles long and at one point more than a mile beneath the crest of the Alps; it therefore gives peculiar facilities for testing the heat of the earth at a point twice as far beneath the surface as any of those upon which the sixty feet ratio was based. Moreover, the rock of Mount Frejus, under which the tunnel runs, is singularly homogenous and almost entirely devoid of sulphurets; nor were any thermal springs detected,

during the process of boring. The ratio of increase in temperature obtained by observations in this tunnel was one degree for every one hundred feet of descent-a rate which is probably nearer the truth than that first named. Prof. Tyndall found the winter temperature of a glacier in the Alps examined by him, at its surface, to be 5o Cent. (23° Fahr.) If we assume that the temperature of our supposed Acadian glacier at its surface was fifteen degrees lower, and the conductive power of ice only onehalf that of solid rock, the heat communicated from the interior of the earth, even at the low rate observed at Mount Cenis, would if the glacier were 5000 feet thick, raise the temperature at its base above the freezing point. It may readily be perceived that this agency would exert a momentous influence on deeply buried glacial ice, converting it into that spongy mass of intimately mingled ice and water which helps to give the glacier its riverlike flow. It may also be inferred, if the relative elevation of the land in different parts of New Brunswick was the same in glacial times as now, that as the glacier did not exceed 5000 feet in thickness the slope of its surface from the Bay Chaleur to the Quaco Hills, could not have been more than one-third of a degree and gravitation could have exerted very little force in pushing it on to the south over this part of its path. Unless the Laurentide Hills stood at much greater elevation then than now, and of this we have no evidence, this part of the glacial sheet (if such existed) must have been a great lake of ice, having no perceptible motion.

GLACIAL EROSION.-A great amount of erosive power has been attributed to glaciers, more perhaps than their known action in Alpine regions will warrant. From an address of Sir R. S. Murchison (this Journal, Feb. 1864), it may be inferred that the glaciers observed by him in the Alps have not the power of pushing out before them even the beds of sand and gravel which lie in their paths, and in some cases scarcely of disturbing the surface of the ground. He cites an instance observed by Mr. Von Der Linth, in which a glacier actually forms a bridge over a narrow gorge in the valley through which it moves. These features in the Alpine glaciers may pethaps be explained upon the grounds taken by Prof. Tyndall in discussing the influence of pressure in reducting the melting point of ice in the glaciers. He very justly infers that the thrust of a glacier is very materially reduced by the obstacles which it encounters in its progress down the mountain