especially the case at the base of cliffs or prominent outcrops, whence a large quantity of material would be easily derived. In other cases material travelled from a distance largely predominates. Throughout the valley of the Lower St. Lawrence, the gneiss and other hard metamorphic rocks of the Laurentian hills to the north-east are very abundant, and in boulders of large size and much rounded. Occasional instances also occur where boulders have been transported to the northwards; but these are comparatively rare. I have mentioned some examples of this in Acadian Geology, p. 61. Similar instances are mentioned in the Geology of Canada, page 893.

Though the boulder clay often presents a somewhat widely extended and uniform sheet, yet it may be stated to fill up all small valleys and depressions, and to be thin or absent on ridges and rising grounds. The boulders which it contains are also by no means uniformly dispersed. Where it is cut through by rivers, or denuded by the action of the sea, ridges of boulders often appear to be included in it. Those on the Ottawa referred to in the "Geology of Canada," page 895, are very good illustrations, and I have observed the same fact on the Lower St. Lawrence and on the coast of Nova Scotia. It is also observable that these lines and groups of boulders are often not of local material, but of rocks from distant localities, and that a number of the same kind seem often to have been deposited together in one group.

Loose boulders are often found upon the surface, and sometimes in great numbers. In some instances these may represent beds of boulder clay removed by denudation. In other cases they may have been derived from the overlying members of the formation, or may have been deposited on the surface, without any covering of clay or gravel. In "Acadian Geology," p. 64, I have illustrated the manner in which large stones, sometimes 8 feet or more in diameter, are moved by the coast ice and sometimes deposited on the surface of soft mud, and I have had oocasion to verify the observations of the same kind made by Admiral Bayfield, and quoted by Sir C. Lyell in the "Principles of Geology." Lastly, on certain high grounds there are large loose boulders, which have probably been moved to their present positions by means of land ice or glaciers.

The Boulder-clay not only presents, as above stated, indications. of successive beds, but it occasionally contains surfaces on which lie large boulders striated and polished on the upper surface, in

the manner of the pavements of boulders described by Miller, as occurring in the Till of Scotland. These appearances are, however, rare, and few opportunities occur for observing them.

A very general and important appearance is the polishing and striation of the underlying rocks usually to be observed under the Boulder-clay, and which is undoubtedly of the same character with that observed under Alpine glaciers. This continental striation or grooving is obviously the effect of the action of ice, and its direction marks the course in which the abrading agent travelled. This direction has been ascertained by the Canadian and United States Surveys, and by local observers, over a large part of Eastern America, and it presents some broad features well deserving attention. A valuable table of the direction of this striation is given in the Geology of Canada, which I may take as a basis for my remarks, adding to it a few local observations of my own. The table embraces one hundred and forty five observations, extending along the valleys of the St. Lawrence and the Ottawa and the borders of the great lakes. In all of these the direction is south, with an inclination to the West and East, or to state the case more precisely, there are two sets of striae, a South-west set and a South-east set. In the table eighty-four are westward of South and fifty-eight are eastward of South, three being due South. It further appears, when we mark the localities on the map, that in the valley of the St. Lawrence and the rising grounds bounding it, the prevailing course is South-west, and this is also the prevalent direction in Western New York, and behind the great Laurentide chain on the North side of Lake Huron. Crossing this striation nearly at right angles, is a second set, which occurs in the neck of land between Georgian Bay and Lake Ontario, in the valley of the Ottawa and in the hilly districts of the Eastern Townships of the Province of Quebec, where it is connected with a similar striation which is prevalent in the valleys of Lake Champlain and the Connecticut River and elsewhere in New England. In New England this striation is said to have been observed on hills 4800 feet high, as for example on Mansfield Mountain, where according to Hitchcock there are striae bearing S. 30° E. at an clevation of 4848 feet. In Nova Scotia and New Brunswick, as

*See also, for the Western districts, Whittlesey's Memoir in the Smithsonian Contributions, and Newberry's Report on Ohio.

in New England, the prevailing direction is South Eastward, though there are also South-west and South striation, and a few cases where the direction is nearly East and West.

It is obvious that such striation must have resulted from the action of a solid mass or masses of ice bearing for a long time on the surface and abrading it by means of stones and sand. It is further obvious that the different sets of striation could scarcely have been produced at the same time, especially when, as is not infrequent, we have two sets nearly at right angles to each other in the same locality. Hence it becomes an important question to ascertain the relative ages of the striation and also the direction in which the abrading force moved.

Taking the valley of the St. Lawrence in the first instance, the crag-and-tail forms of the isolated hills of trap, like the Montreal mountain, with abrupt escarpments to the north-east and slopes of debris to the south-west, the quantity of boulders carried from them far to the south-west, and the prevailing striation in the same direction, all point to a general movement of detritus up the St. Lawrence valley to the south-west. Further, in some cases the striae themselves show the direction of the abrading force. For example, in a fine exposure recently made at the Mile-end quarries, near Montreal, the polished and grooved surface of the limestone shows four sets of striae. The principal ones have the direction of S. 68° W. and S. 60° W respectively, and the second of these sets is the stronger and coarser, and sometimes obliterates the first. The two other sets are comparatively few and feeble striae, one set running nearly N. and S., and the other N.W. and S.E. These last are probably newer than the two first sets. Now with regard to the direction of the principal sets of striae, this at the locality in question was rendered very manifest by the occurrence of certain trap dykes crossing the limestone at right angles to the striae. The force, whatever it was, had impinged on these dykes from the N. E., and their S. W. side had protected the softer limestone. The locality is to the North-east of the mass of trap constituting the Montreal mountain, and the movement must have been up the St. Lawrence valley from the N.E., and toward the mountain, but at this particular place the striae point West of its mass. This, I have no hesitation in saying, is the dominant direction in the St. Law rence valley, and it certainly points to the action of the arctic current passing up the valley in a period of submergence. Fur

ther, it is the Boulder-clay connected with this S. W. striation. that has hitherto proved most rich in marine shells.

If, however, we pass from the St. Lawrence Valley up the valleys which open into it from the North, as for example the gorge of the Saguenay, the Murray Bay River, or the Ottawa River, we at once find a striation nearly at right angles to the former, or pointing to the South-east.

At the mouth of the Saguenay, near Moulin Bode, are striae and grooves on a magnificent scale, some of the latter being ten feet wide and four feet deep, cut into hard gneiss. Their course is N. 10° W. to N. 20° W. magnetic, or N. 30° to 40° W. when referred to the true meridian. In the same region, on hills 300 feet high, are roches moutonnees with their smoothest faces pointing in the same direction, or to the North-west. This direction is that of the valley or gorge of the Saguenay, which enters nearly at right angles the valley of the St. Lawrence. At the month of the Saguenay the Lark Shoals constitute a mass of debris and boulders, both inside and outside of which is very deep water; and many of the fragments of stone on these shoals must have been carried down the Saguenay more than fifty miles.

In like manner at Murray Bay there are striae on the Silurian limestones near Point au Pique, which run about N. 45° W. but these are crossed by another set having a course S. 30° W., so that we have here two sets of markings, the one pointing upwards along the deep valley of Murray Bay River to the Laurentide Hills inland, the other following the general trend of the St. Lawrence valley. The Boulder-clay which rests on these striated surfaces is a dark-coloured Till, full of Laurentian boulders, and holding Leda truncata, and also Bryozoa clinging to some of the boulders. In ascending the Murray Bay River, we find these boulder-beds surmounted by very thick stratified clays, with marine shells, which extend upward to an elevation of about 800 feet, when they give place to loose boulders and unstratified drift. About this elevation, the laminated clays meet a ridge of drift like a moraine, crossing the valley, which forms the barrier of a small lake, Petite Lac, and a second similar barrier separates this from Grand Lac. If the valley of Murray Bay River was occupied with a glacier descending from the Laurentian hills inland, which are probably here 3000 to 4000 feet high, this glacier or large detached masses pushed from its foot, must have at one time extended quite to the border of the St. Lawrence, and at

another must have terminated at the borders of the two lakes above mentioned.

On a still larger scale the N. W. and S. E. striation appears in the valley of the Ottawa, and farther west between the head of Lake Ontario and Lake Huron. In these places there is no elevation capable of giving rise to local glaciers, and therefore, as in New England and Nova Scotia, we must ascribe the glaciation either to general ice-laden currents from the North-west, or to the great continental glacier imagined by some geologists.

A most important observation bearing on this subject appears in the Report of Mr. R. Bell, in the region of Lake Nipigon, North of Lake Superior. He observed there the prevailing South-west striation, but with a more westerly trend than usual. Crossing this, however, there was a southerly and S. E. set of striae which were observed to be older than the South-west striae. In some other parts of Canada these striae seem to be newer than the others, but there would be nothing improbable in their occuring both at the beginning and end of the Boulder-clay period.

In summing up this subject, I think it may be affirmed that when the striation and transfer of materials have obviously been from N.E. to S.W., in the direction of the Arctic current, and more especially when marine remains occur in the drift, we may infer that floating ice and marine currents have been the efficient agents. Where the striation has a local character, depending upon existing mountains and valleys, we may on the other hand infer the action of land ice. For many minor effects of striation, and of heaping up of moraine-like ridges, we may refer to the presence of lake or coast ice as the land was rising or subsiding. This we now see producing such effects, and I think it has not been sufficiently taken into the account.

As to the St. Lawrence valley, it is evident that its condition during the deposit of the Boulder-clay must have been that of a part of a wide sound or inland sea extending across the continent, and that local glaciers may have descended into it from the high lands on the north and possibly also on the south. During this state of the valley great quantities of boulders were bronght down into it, especially from the Laurentide hills, and were drifted along the valley, principally to the south-west. Extensive erosion also took place by the combined action of frost, rain, melting snows, and the arctic current and the waves, and thus was furnished the finer material of the Boulder-clay.