more than 1150 feet. The possibility of this opens a wide question, not only in regard to terrestrial physics, but also as to the interpretation of the glacial deposits in the British Isles. This question will be noticed in a later chapter. If it can be proved that a submergence to more than the above amount actually took place on the southern side of the Border, there would be nothing startling in its effects extending to Western Scotland. If, however, the deposits in question testify to elevation rather than to depression, then the objections to the marine hypothesis become almost insuperable. The other difficulty, that of the absence of any marine organism, both in the roads and at any other like elevation in Scotland, though it may be explained, as has been mentioned above, is undoubtedly a grave one. The main objections to the fresh-water hypothesis (apart from the question of a submergence) turn upon the difficulty of accounting for the existence of a mass of ice huge enough to act as a dam for such a body of water, under circumstances which would allow of Glen Roy, with parts of some neighbouring valleys, being free from ice.1 Hence, as there are difficulties on all sides, the history of the Parallel Roads of Glen Roy is likely to remain for the present among the controversial questions of geology.

Much has been written about certain ridges of

1 The gravity of this will be better appreciated after a study of some of the later chapters of this book.

1

débris more or less water-worn, which are variously called Kames, Eskers, or Åsar (pronounced Osar); and though they are generally admitted to be among the phenomena of a Glacial Epoch, the question of their origin is hardly yet settled. These kames are ridges, sometimes sharp, sometimes comparatively flat at the top, which run across the country, following generally the direction of the main streams, though not always exactly taking the same course, or keeping to the lowest ground. Occasionally they may be traced continuously for many miles,2 "running like great artificial ramparts across the country; sometimes they terminate abruptly. In external aspect they often present a general resemblance to a lateral moraine, but differ from it internally in being composed of materials more or less water-worn, and in exhibiting a stratification which often is most distinct. Very commonly the beds are arranged with a certain relation to the form of the mass, and are seen in a transverse section to slope outwards roughly parallel with its sides, or even to form a series, though an irregular one, of concentric arches. A group of them will be described more fully in connection with the glacial deposits of Ireland, in the

1 The first name, of Scotch origin, means "comb." "Ås," in Swedish, is a beam, and is used sometimes for a hill-ridge, "åsar" being the plural. Full accounts of them are given in Professor J. Geikie's "Great Ice Age," chaps. xiv. and xxxi., and in Dr. Wright's "Ice Age of North America," chap. xiv.

2 Erdmann, quoted by Professor J. Geikie, gives instances of åsar in Sweden varying in length from 125 to over 200 miles.

lowlands of which country, as of Scotland, they are commoner than in England. They have been recognised in Northern Germany, in the neighbourhood of the Baltic; they are abundant also in parts of Scandinavia, Finland, and Russia, and of North America. To quote from Professor J. Geikie's excellent description,1 they are at any rate in the Baltic coast-lands-of later date than the youngest boulder clay of that region, upon which they sometimes rest, but oftener perhaps on solid rock. They rise abruptly to a

N.W.

FIG. 11. Section of Kame near Dover, New Hampshire. Length, 300 feet; height, 40 feet; base, about 40 feet above the Cocheco River, or 75 feet above the sea. a, a, grey clay; b, fine sand; c, c, coarse gravel containing pebbles from six inches to one foot and a half in diameter; d, d, fine gravel. (Upham.).

height of from 50 to surface of the ground. reach as much as 180 feet, while now and again they sink down to 30 or 20 feet, or even disappear altogether below newer deposits. Their sides have an inclination of from 15° to 20°, but occasionally as much as 25° or even 30°, and the two declivities very rarely slope at the same angle. Often beginning

100 feet above the average "Sometimes, however, they

Loc. cit., chap. xxxi.

S. F

in the interior of the country, the åsar follow the valleys down to the low coast-land, across which they pass as well-defined ridges out to sea, after a course of not infrequently more than a hundred English miles. In the mode of their distribution they show a striking resemblance to river-courses. . . . At greater heights than 300 feet above the sea these remarkable ridges are, as a general rule, confined to the valleys, but at lower levels they seem to be tolerably independent of the present configuration of the ground. They are met with at all levels up to and above 1000 feet. The materials of which they are composed may consist either of coarse shingle, or of pebbly gravel, or of sand, or it may be made up of all three. In some parts of a ridge shingle and gravel predominate, in others sand is the principal ingredient. In one place the stratification may be distinct, in other places obscure."

As a rule, according to Professor J. Geikie, the stones in the gravel of these kames or åsar are well rounded and water-worn, though exceptions to this are occasionally found, the deposits being unstratified and earthy, and the stones subangular, or even angular; the one type of deposit being associated with the other in a way that shows them to be connected. Erratics are rarely embedded in the gravels, but are not unfrequently found dotted over the tops and slopes of the hillocks, as if they had been dropped upon the surface.