are set in the most delicious emerald framework of Parsley-ferns. The slopes of the Millstone-Grit hills of Lancashire and Derbyshire-where they allow of the detached rocks coming to rest on their surfaces, and are not too steep to force them to roll to the base before they can stop-are often delightful paradises of ferns and other rare plants, which nestle beneath the shelter of these reposing stones. A wildness, truly, does a hill-slope like this produce, of gnarled saplings, angular moss-grown stones, lichen-clad boulders, damp, oozing-moss tracts, out of which emerge sparkling mountain streams, with banks verdant with liver-wort and jungermannias.

This old crop of rolled fragments gradually weathers away, and the mountain streams carry off the detritus in the shape of large sand-grains. But a new crop succeeds the old; and in this manner, through the silent but unresting centuries, the highest mountains are brought low, whilst the valleys are being exalted.

Let us turn to one other special agency we can see at work sculpturing the mountains and hills into characteristic shapes, or giving to them some of their best-known features. The rills and waterfalls which carry off the drainage of the heavier rain-falls that usually visit mountainous regions are wonderful natural implements for sawing their rocky beds backwards; and it requires little special training for the student to see them at work in every stage and degree of development along every mountain flank. Possibly, during some walking tour in North Wales or the Lake District, the evening has been inaugurated by a steady downpour of rain, which has continued

persistently all night, and only ceased the following morning. Then the morning sun has broken forth. with more than summer glory. The hills and meadows are bespangled with raindrops, each of which reflects the sunshine. The brooks and rivers have risen in turbulent volume, and continued to be swollen

all the day by the contributions of the mountain torrents. Every mountain side is seamed with what appear to be silvery threads, but which we know are the improvised rills carrying off the excessive rainfall. They only appear on occasions like these. Here and there, perchance, is a more regular water

course, in whose bed you discover a miniature rill even on the hottest and dryest day in summer. It is the home of the dipper, or water-ousel, who finds. abundance of insect-life among the moss-clad stones which abound in such a gorge. Possibly you may see defiles deeper and larger still-in short, we get them of all "sizes," from the gutter-like seam which marks the presence of a temporary rill in rainy weather, to deep and even awful clefts, along whose bottom there is one perpetual roar of running water.

Examine any or all of these various-sized indentations in the mountain or hill-side, and you will invariably see their beds bouldery and rocky, and full of all sorts of loose fragments of stone. We have said that anyone might find an almost imperceptible gradation in the various rills, between the smallest and most insignificant, and the deepest and gloomiest gorge. The origin of the latter now suggests itself. We can easily see that after a heavy rainfall, when the descending waters are rushing down the watercourses, all the boulder and rock fragments lying along the bed will be set in motion. Their mechanical action wears the channel deeper and wider, and when this agency has been in operation for unnumbered thousands of years, that which was once a mere indentation down where a silvery mountain stream found its way after a storm, will have become a "burn," a "glen," or a gorge." In this way there can be little doubt that all such wild clifts or bonny mountain glens have been mechanically excavated by the action of running water. We have seen how ancient our British mountains are geologi

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cally, and we have therefore no difficulty in giving to agents still in operation an abundance of time for them to eat out the most wonderful of our mountain gorges, glens, and even such passes as those of Glencoe, Llanberis, and Aberglaslyn. So awe-inspiring are some of the rifts which thus appear in the solid rocks that even intelligent people feel bound to explain them by reference to earthquake shocks. But the beds of the streams show that the rocks are continuous across. There is no fissure or cleft such as would be produced if the defile had been rent open. Every geological observation leads to the conclusion that this characteristic kind of mountain scenery has been due to the "small, still voice" of rills and streams, silently but perpetually operating during innumerable ages! Every waterfall and cataract wears backwards the ledge over which its waters are precipitated, and thus, like a vertical saw, each gorge is slowly eaten backwards into the heart of the hills.

The minor glen-scenery of hilly districts has very probably originated since the close of the Glacial period. That was the last of the great and important geological epochs, and it immediately preceded the appearance of Man upon the face of the earth. It was a most important period in many respects, but in none more than the way in which it gave the last finishing touches to the scenery of our hills and mountains. As the name given to it by geologists indicates, it was an age peculiar for the extreme cold which then prevailed over the whole northern hemisphere. The probable origin of this cold period is not unknown to astronomers and geologists. Suffice it for us at

present that there is abundant evidence to prove it continued in force for many thousands of years, with intervals of comparatively warmer conditions. At the

earlier part of the Glacial period our British hills and mountains were loftier than they are now, for they suffered subsequently severely by glacial denudation.