Only a few of the higher summits in the New England region approach the scenic conditions usually associated with truly lofty mountains. In fact, the general lack of rugged escarpments as well as of great elevation leads the geographer to rank even the highest of these rounded summits as hills of large size rather than attempt to burden them with the dignity that the term mountain carries with it. They are beautiful hills, separated one from another by lovely valleys, which draw the beholder to them and fill his memory with tender longings and vague dreamy fancies such as the sterner grandeurs of great mountains fail to awaken.
The Laurentian Highlands.—A vast area in the eastern portion of Canada, to the north of the valley of the St. Lawrence, including Labrador, is underlaid by very ancient crystalline rocks of the same general character as those forming the Adirondacks. This same geological system, the Archean, has a wide development in the continental basin to the north of Lake Superior and about Hudson Bay. To the north of Quebec, in the region drained by the Saguenay and Ottawa Rivers, the land has a general elevation of 1,500 to 1,600 feet, and is known as the Laurentian Highlands, although sometimes dignified by the name Laurentian Mountains, or, more briefly, as the Laurentides. In reality, this broad, indefinitely defined region from a geographical point of view is a roughened plateau and not a mountain range or group of ranges. When the structure and metamorphosed condition of the rocks are considered, however, it is found that they have the characteristics pertaining to the central and more deeply seated portions of true mountains. The rocks are mainly crystalline schist, gneiss, granite, etc., together with igneous intrusions, all of which have been intensely folded, crumpled, and broken. The general interpretation of the existing conditions is that deep erosion has occurred and, in fact, a mountain range or a mountain chain worn down to a generally plane surface. The thickness of the rocks thus removed, or the depth of erosion, is unknown, and owing mainly to the complexity of the geological structure of the terranes remaining, will
perhaps never be ascertained, but can be safely estimated as not only hundreds, but several thousands of feet. Erosion has laid bare portions of the earth's crust which were once deeply buried, and reveals the character of the "basement complex," as it has been termed, which forms the foundation of the continent. Owing to the great age of the rocks and the depth to which they were once depressed in the earth's crust, they have experienced great changes. They are not only intensely folded and crushed, but in large part have been caused to flow under great pressure, and have thus acquired a schistose structure. Fissures have been filled with molten rock injected from below so as to form dikes, and possibly still greater or regional intrusions have occurred. Over large areas the amount of once molten and intruded rock exceeds the surface exposure of what are usually, but with some hesitation, classed as metamorphosed sediments.
Long exposure to the air in a region of mild relief is usually accompanied by the formation of a deep soil. The soil over the Laurentian Highlands, however, is generally thin, and large areas of bare rock are exposed. The explanation of this apparent anomaly is that glaciers during a geologically recent period were formed on this region and flowed away from it, carrying most of the previously formed rock débris with them. The time since the melting of the glaciers has been too short for a new soil to form, except in the valleys and depressions among the bare glaciated hills, which hold a peaty accumulation resulting from the partial decay of vegetation. The scarcity of soil is also due in part to the climatic conditions now prevailing, which are unfavourable to rapid rock decay.
To the north of the Laurentian Highlands and in the vicinity of Hudson Strait, the land becomes higher, and as recently reported by Robert Bell, of the Canadian Geological Survey, forms true mountains with elevations in the neighbourhood of 8,000 feet. What revelations are to come from the inhospitable and in large part ice-covered lands still farther north can only be told as exploration and surveys are extended in that direction.
This brief review of some of the leading characteristics of the mountains and hills adjacent to the Atlantic coast will, I think, serve to show that they bear a family relationship; like the members of a family, they are of various ages, although all of them are past their prime, and may with propriety be termed the Atlantic Cordillera.
THE CONTINENTAL BASIN
An inspection of the map forming Fig. 14, on which the larger geographical features of North America are indicated, will assist the reader in appreciating the general relations and extent of the plains and plateaus which collectively form the Continental basin.