=The “parallel roads” of the Scottish glens.=—In a number of neighboring glens within the southern highlands of Scotland there are found faint terraces upon the glen walls which under the name of the “parallel roads” (Fig. 349) have offered a vexed problem to scientists. Of the many scientists who long attempted to explain them, though in vain, was Charles Darwin, the father of modern evolution. He offered it as his view that the “roads” were beaches formed at a time when the sea entered the glens and stood at these levels. When, however, Jamieson’s studies had discovered their true history, Darwin, with a frankness characteristic of some of the greatest scientists, admitted how far astray he had been in his reasoning. Let us, then, first examine the facts, and later their interpretation. The map of Fig. 350 will suffice to set forth with sufficient clearness the course of the several “roads.” These “roads” are found in a number of glens tributary to Loch Lochy, and of the three neighboring valleys, Glen Roy has three, Glen Glaster two, and Glen Spean one “road.” The facts of greatest significance in arriving at their interpretation relate to their elevations with reference to the passes at the valley heads, their abrupt terminations down-valleyward, and the morainic accumulations which are found where they terminate. The single “road” of Glen Spean is found at an elevation of 898 feet, a height which corresponds to that of the pass or col at the head of its valley and to the lowest of the “roads” in both Glens Glaster and Roy. Similarly the upper of the two “roads” in Glen Glaster is at the height of the pass at its head (1075 feet) and corresponds in elevation to the middle one of the three “roads” in Glen Roy. Lastly, the highest of the “roads” in Glen Roy is found at an elevation of 1151 feet, the height of the col at the head of the Glen. In the neighboring Glen Gloy is a still higher “road” corresponding likewise in elevation to that of the pass through which it connects with Glen Roy. [Illustration: FIG. 350.—Map of Glen Roy and neighboring valleys of the Scottish highlands with the so-called “roads” entered in heavy lines. Glens Roy, Glaster, and Spean have three “roads”, two “roads”, and one “road”, respectively (after Jamieson).] To come now to the explanation of the “roads”, it may be said at the outset that they are, as Darwin supposed, beach terraces cut by waves, not as he believed of the ocean, but of lakes which once filled portions of the glens when glaciers proceeding from Ben Nevis to the southwestward were blocking their lower portions. The several episodes of this lake history will be clear from a study of the three successive idealistic diagrams in Fig. 351. [Illustration: FIG. 351.—Three successive diagrams to set forth in order the late glacial lake history of the Scottish glens.]