drew of London. I am also indebted to Mr. G. S. Brady for determining the Ostracoda, to the Rev. H. W. Crosskey for opportunities of comparing specimens with those of the Clyde Beds, and to Prof. T. R. Jones and Dr. Parker and Mr. G. M. Dawson for help with the Foraminifera.

The present memoir will, I am sure, be welcomed by all who are engaged in the study of the subject to which it relates, if for no other reason, because the Post-pliocene deposits of Canada from their great extent and perfect development, are well fitted to throw light on many of the controversies which are now agitated with regard to these deposits.

It may be proper here to indicate the nomenclature which will be followed. When the whole geological series is divided into Primary, Secondary, and Tertiary, the deposits to which this paper relates are usually named Post-tertiary or Quaternary. These terms are, in my judgment, unfortunate and misleading. If we take the relations of fossils as our guide, then, as Pictet has well remarked, whether we regard the land or the sea animals, there is no decided break between the Newer Pliocene and the Post-pliocene, the changes not being greater than those between the Pliocene and the older Tertiary ages. There is, therefore, no such thing in nature as a Quaternary time distinct from the Tertiary, as the Tertiary is distinct from the Secondary. Where therefore the terms Primary, Secondary, and Tertiary are used, the latter should include the whole time from the Eocene to the modern, inclusive, unless indeed the advent of man be considered an event of sufficient geological importance to warrant a separation of the modern from the Tertiary period. When the terms Palæozoic, Mesozoic and Kainozoic or Neozoic are used, then the two latter terms cover perfectly the Post-pliocene as well as the Eocene, Miocene and Pliocene.

I would therefore include the Post-pliocene in the Neozoic or Tertiary period and define it to be that geological age which is included between the Pliocene and the Recent. From the former it is separated by the advent of the cold or glacial period, and the accompanying subsidence of the land, as well as by the disappearance of many species of animals and plants. From the latter it is separated by the extinction of many mammalian

* I use the term "glacial" in this paper in its general sense, as including the action of floating ice as well as of land ice.

forms and by the establishment of our continents at their present elevation above the water and with their present fauna and flora and drainage systems. In Canada the absence of the Pliocene deposits and the immediate superposition of the Post-pliocene on the Palaeozoic formations, remove all difficulty on the subject of the beginning of the period. The line of separation between the Post-pliocence and the recent, especially in Western Canada, is less distinct; but in Eastern Canada the upper part of the Postpliocene is always marine, while the recent deposits are land and fresh-water.

With regard to the subdivisions of the Post-pliocene in Canada, if we confine our attention to the clearly marked marine and glacial beds of the lower part of the St. Lawrence Valley, we have no difficulty in establishing the following divisions, suggested in my paper of 1857:

3. Saxicava Sand, shallow-water sand and gravels, equivalent to the Champlain and Terrace epochs in part of Dana, to the modified drift of Hitchcock in part, to the Tertiary sands of Capt. Bayfield; and to the Upper fossiliferous sands and gravels of Scotland and Scandinavia. Leda Clay, moderately deep-water clays, equivalent to lower part of Champlain epoch, Dana, and Tertiary clays of Bayfield. Fossiliferous Clays of Scotland and Scandinavia.

2.

3. Boulder-Clay.-Hard clay or sometimes sandy clay or sand, with stones and boulders, and not distinctly laminated. Equivalent to Glacial clays of Dana and unmodified drift of Hitchcock. Till and older Boulder clay of Scotland and Scandinavia.

In Lower Canada these three deposits can often be seen in actual superposition, and the order is invariable. In some places all contain marine shells, in others these are limited to the upper part of the Leda clay or the lower part of the Saxicava sand.

In Western Canada, around the great lakes, are extensively distributed beds of clay and gravel, which have been described in the Report of the Geological Survey, and which have afforded freshwater and land remains only. Of these the Algoma sand and Saugeen clay and sand may possibly correspond in age to the Saxicava sand, and the Erie clay to the Leda clay. This identification is, however, uncertain, as the marine Leda clay has been traced up no further than the vicinity of Kingston, on the St.

Lawrence, and of Arnprior on the Ottawa. Below these points the Valleys of the Ottawa and St. Lawrence present everywhere the deposits above tabulated, in a greater or less degree of completeness. They are connected with the similar deposits of New England, through the valley of Lake Champlain, and across the low lands of Nova Scotia and New Brunswick.

Whittlesey has described the Western Drift Deposits in the Smithsonian Contributions, vol. xv., and according to him the Boulder drift is there the upper member of the series. More recently Prof. Newberry has given a summary of the facts in his Report of the Geological Survey of Ohio for 1869. From these. sources I condense the following statements,

The lowest member of the Western drift, corresponding to the Erie clays of the Canadian Report, is very widely distributed and fills up the old hollows of the country, in some cases being two hundred feet or more in thickness. Toward the north these clays contain boulders and stones, but do not constitute a true Boulder-clay. They rest, however, on the glaciated rock surfaces. They have afforded no fossils except drifted vegetable remains.

Above these clays are sands of variable thickness. They contain beds of gravel, and near the surface teeth of elephants have been found. On the surface are scattered boulders and blocks of northern origin, often of great size, and in some cases transported two hundred miles from their original places.

More recent than all these deposits are the "Lake Ridges" marking a former extension of the great lakes. Dr. Newberry considers the Erie clay to be the deposit of a period of submergence following the action of a continental glacier, and he maintains that the old channels now filled with Erie clay are so deep as to indicate that in the earlier glacier period the land was at least five hundred feet higher than its present level. At the close of this period of submergence the boulder drift was deposited by northern currents and ice, and then the land gradually rose to its present level.

The facts thus summed up by Dr. Newberry indicate, in proceeding from the older to the newer.

1. An elevated continent and the erosion of deep valleys. 2. Glaciation of the surface.

3. Filling of the valleys with Erie clay.

4. Distribution over the surface, of boulders and Northern drift.

My interpretation of the phenomena would differ from that of Dr. Newberry in the following particulars-(1) I would refer the continental elevation and the deep erosion to the Pliocene period, before the advent of the glacial epoch. (2) I would refer the glaciated surfaces and the lower part of the Erie clay to the time of the Canadian Boulder-clay, and would regard it as an evidence of subsidence and an ice-laden sea, with the arctic current passing over the continent from the North-East. (3) I would regard the upper part of the Erie clay as equivalent to the Leda clay. (4) I would place the upper and confessedly water-borne drift as the equivalent of the Saxicava sand, and as belonging to the period of elevation.

It is a difficulty, both in Dr. Newberry's view and mine, that marine shells are not found in the Erie clay and surface drift. The following considerations, however, diminish this. (1) The greater part of the Leda clay is very poor in fossils, even near the ocean, and so is the boulder clay. (2) The submergence of a vast continental area under cold water might have continued for a long time before the marine animals could widely spread themselves over it, especially under the unfavourable circumstances of ice erosion. (3) The few and scattered marine remains to be expected in these deposits may have escaped observation. The occurrence of much drift-wood in the Erie clay is also, in my judgment, inconsistent with the occurrence of a general glacier immediately previous to the deposition of the clay.

We may now consider the several members of the Post-pliocene in succession, beginning with the oldest.

Throughout a great part of Canada there is a true "Till," consisting of hard gray clay, filled with stones and thickly packed with boulders. In some places, however, the clay becomes sandy, and in some portions of the carboniferous areas, the paste is an incoherent sand. The mass is usually destitute of any stratification or subordinate lamination; but sometimes in thick beds horizontal lines of different texture or colour can be perceived, and occasionally the clay intervening between the stones becomes laminated, or at least shows such a structure when disintegrated by frost. The Boulder-clay usually rests directly on striated rock surfaces;

but I have observed in Cape Breton a peaty or brown coal deposit, with branches of coniferous trees, to underlie it, and in other places there are deposits of rolled gravel under the Boulderclay. At the Glen brick-work, near Montreal, a peculiar modified Boulder-clay occurs, consisting of very irregularly bedded sand and gravel, with many large boulders, and only thin layers of clay.

The stones of the Boulder-clay are often scratched and ground into those peculiar wedge-shapes, so characteristic of ice-worked stones. Very abundant examples of this occur in the Boulder clay of Montreal and its vicinity.

At Isle Verte, Riviere du Loup, Murray Bay, Quebec, and St. Nicholas, on the St. Lawrence, the Boulder-clay is fossiliferous, containing especially Leda truncata, and often having boulders and large stones covered with Balanus Hameri and with Bryozoa, evidencing that they have for some time quietly reposed in the sea bottom before being buried in the clay. This is indeed the usual condition of the Boulder-clay in the lower part of the St. Lawrence River. Further up, in the vicinity of Montreal, it has not been observed to contain fossils, but it presents equally unequivocal evidence of sub-aqueous origin in the low state of oxidation of the iron in the blue clay, which becomes brown when exposed to the weather, and in the brightness of the iron pyrites contained in some of the glaciated stones, as well as in the presence of rounded and glaciated lumps of Utica shale and other soft rocks, which become disintegrated at once when exposed to weathering.

The true Boulder-clay is in all ordinary cases the oldest member of the Post-pliocene deposits, and it is not possible to ascertain the existence of Boulder-clays of different ages, superimposed on one another. It may be observed, however, that in so far as the Boulder-clay is a marine deposit, that which occurs at lower levels is in all probability newer than that which occurs at higher levels. It is also to be observed that boulders with layers of stones occasionally occur in the Leda clay; and that the superficial sands and gravels sometimes contain large boulders; but these appearances are not, I think, sufficiently important to induce any experienced observer to mistake such overlying deposits for the true Boulder clay.

In some localities the stones in the Boulder-clay are almost exclusively those of the neighbouring rock formations, and this is