GLEN'ROY, PARALLEL ROADS OF. The Roy is a small stream in the district of Lochaber, Invernessshire, having a course of about 15 m., and falling into the Spean at Inverroy, opposite to Ben Chlinaig, the eastern spur of Ben Nevis. The steep, nar row valley through which the Roy runs is remarkable for having its faces marked with three shelves, which appear as' lines running right round it; they are everywhere per fectly horizontal and parallel to each other, and in each case the line on one side of the glen corresponds exactly iu elevation to that on the other. The granitic and metamor phic rocks, of which the mountains are composed, are covered with a greater or less thickness of angular fragments and earth, and an examination of the shelves shows that they are worn out of this soft alluvial coating. They almost invariably form a gentle slope from the hillside, and are from 3 to 30 ft. wide. The protrusion of the rocky body of the mountain, and the furrows of mountain torrents, break their contin uity, but with these exceptions one or more of them may be traced along the whole valley. - The highest, which is 1139i ft. above the sea-level, is easily followed from the watershed between the Roy and the Spey (which is at the same elevation), along both sides of the valley, as far down as the point at which the valley narrows above Glen Glaster. The second shelf is 80 ft. lower, runs parallel with the first all round the head of the valley, and is continued further down until it includes Glen Glaster. The third line is 212 ft. lower than the second; it may be traced along both sides of Glenroy, and round time mouth of the glen into the valley of the Spean, whose sides, at the same ele vation of 847 ft., is marked from within 3 in. of the river Lochy up nearly as far as loch Lagan. What is very curious, the elevation of the highest shelf corresponds with that of the watershed at the head of Glenroy (where it opens towards the valley of the Spey): the second corresponds with the watershed at the head of Glen Glaster (where it opens towards Glen Spean); and the third is at the same level with the valley of passage between Spean and Spey at Muckall. There is yet a higher shelf in the
neighboring Glen Ginoy, at an elevation of 11591 ft. above the sea.
Many attempts have been made to explain the origin of these remarkable shelves. Their forming somewhat level roads around the valley originated the popular notion that they were made for the convenience of the heroes whose exploits are sung by Ossiau. Playfair, in 1816, supposed. they were aqueducts for artificial irrigation. .fac culloch believed them to be the shore-lines of fresh-water lakes, which gradually washed away their barriers, remaining for a longer space at the height of the various shelves. Sir T. D. Lauder embraced and illustrated the same view. Darwin considered that the glens were former arms of the sea, and that the shelves indicated periods of rest in the elevation of the land. Agassiz and Buckland returned to the opinion of Maccullocb, but finding no indication or remains of any solid land barrier, they referred the lake to the glacial period, and held that two large glaciers came down from Ben Nevis, the one near the center of the mountain, and the other along the basin of 'Loch Treig, and that these dammed up the water in the included portion of Glen Spean and in Glenroy. In a paper subsequently published by Mr. David Milne, the lacustrine theory was reverted to, with several new and plausible illustrations. The reader is referred to a work of Mr. R. Chambers (Ancient Sea-margins, 1848) for a full account of this remarkable dis trict. He enumerates no less than 21 terraces or shelves, in addition to the four prom inent ones already described, at heights varying from 325 to 1495 feet. And uniting all these into a regular series, lie endeavors to show that they are owing to the recession of the sea from these glens, and that the intensity of the shore-markings depended upon the angle at which the hill met the water, the nature of the surface of the hill, and the quietness of the water.