of the high ground of the elevated table-land for the weather agencies afterwards to operate upon, to eat into, and eventually to produce the present landscape effects by removing the softer strata, leaving the hard masses standing base to base as hills and mountains. This is sometimes the case when the same strata dip at a lower angle, for if we follow the same beds of rock over great distances we shall often find them relatively soft and hard. When the rock-masses were elevated we may be sure that atmospherical wear-and-tear would soon find out the weakest and easiest places to operate upon, and there, in the long

Section across a Hilly Range, showing Strata of same angle of dip, but of different degrees of hardness, the hardest rising highest.

run, we should have hollows scooped or eaten out. The drainage of the surface water would naturally be along the excavated places, and so would assist in still further deepening them, until eventually valleys would be formed, in some of which rivers would meander. When a formation had its beds upheaved from their horizontal position, it would be foolish, indeed, to expect that all the strata would have just the same degree of hardness over a large tract of country. If they had not, then we may reasonably expect to find the softest of them eaten away the most, so that the outcrops of the hard rocks would take place on the loftiest parts of the hilly range.

Every kind of rock has its own style of weathering,

and a skilful geologist can actually tell a geological formation by the scenery of its surface, by the shape of its hills, and the contour of its valleys. Chalk is usually marked by the round-topped hills we call "Downs ;" granite weathers into elevated rolling moorland; gneiss, mica-schist, and metamorphic rocks generally form the most inaccessible mountains, having needle-shaped peaks; carboniferous limestone is usually characterised by a terrace-like arrangement, according to the dip of its strata, and by the presence of numerous gorges and narrow "dales," like those of Derbyshire and Yorkshire. The Yoredale Rocks, the Lias Shales, the Oxford Clay, Kimmeridge Clay, and London Clay, are usually met with in large valleys, plains, and fens, because the softness of these strata has caused them to be weathered to the lowest level, and, as they hold surface water, they usually produce fenny or boggy areas. The "fens" of Cambridgeshire, Norfolk, and Lincolnshire, and the "marshes" of Essex, are all underlaid by one or other of the above-mentioned soft clayey formations.

In the saddle-shaped (anticlinal) and basin-shaped (synclinal) curves into which the strata of a district have been bent, it might be thought that the former produced mountains and the latter valleys. Such an assumption, however, would be totally without proof. The shapes of our hills and mountains are altogether independent of the flexures into which the rocks. composing them have been thrown. Synclinal or basin-shaped depressions of strata are quite as likely to be found on mountain-tops as in the valleys beneath. In not a few instances the summits of our

hills contain fragments of ancient valleys, as is the case with the Scuir of Eigg.

It is more than probable that all our oldest British mountains stand at a less altitude now than they have done for millions of years past. For during that time they have been exposed to various weatheraction, which has stripped or peeled off large quantities of rocky material even from the hardest of them. Meantime the valleys have been gradually widening, and eating farther into the heart of the hills; and not unfrequently we find instances where the valleys have been thus carried back from two opposite directions, until there is only a thin partition of rock-barrier now separating them. Given time enough and a continuance of the same weathering action, and eventually even this barrier would be eaten away, and the two valleys be thrown at last into one. There can be little question that this mode of forming one large valley out of two smaller ones has often taken place in the physical history of our mountains.

How even the hardest and ruggedest of rocks suffer from the action of the weather is curiously illustrated in many of the hilly districts of Great Britain. Along the crests of some ranges of hills we may see piles of stones, one upon another, to which the names of "Cheese-wrings," "Cakes-of-bread,” &c., are popularly applied. We may see them to perfection along the crest of the Millstone-Grit which is crossed on the road from Sheffield to Castleton, in Derbyshire. The lower stones are frequently of narrower diameter than the upper, owing to the

mechanical action of the dust wearing away the base. These stones, piled on each other like cheeses, are simply so many surviving fragments of once-continuous strata, all of which have gone except these miniature "outliers," existing to indicate the amount of wear-and-tear which has taken place even since the conclusion of the "Glacial period.” An observer may easily perceive, by noticing how these piled stones are more or less continuous in their arrangement, that they represent strata of solid rock which have been weathered away to at least a thickness amounting to the highest point of the "cheese-wrings." Not unfrequently these rounded stones are so delicately poised that they have been, and still are, regarded with superstitious awe by the unlearned. They are looked upon as the work of demons, fairies, or oftener still, of Druids. The name of "Druids' stones" is frequently given to them, especially in Cornwall. These weathered blocks are of commoner occurrence in Palæozoic rocks than any other. In Granitic districts, as on Dartmoor, we may often see rounded piles of granite, like so many heaps of boulders, each rounded mass being weathered everywhere except where it is protected by the surface of the overlying stone. Sometimes great masses weather, in situ, in such a manner all over them, that the base rests on a point so small that the block can be easily rocked to-and-fro. Such rounded, weathered, and delicately-poised blocks are called "Logans," or "Rocking-stones." In Cornwall these have even been called by individual names, as the "Nut-cracker," in Lustleigh Clewe, Devonshire.

One of the best known is situated near Castle Treryn, St. Leven, Cornwall. Its size is about 17 feet in length, and more than 32 in the circumference of its middle part; the total weight being calculated at about sixty-five tons. A "Cheese-wring" which occupies the highest ridge of a hill north of Liskeard, in Cornwall, is piled up to the height of 17 feet. Most people who have visited Dartmoor, Torquay and Newton-Abbot will vividly bear in mind. the conspicuous appearance of another of these evidences of atmospherical waste known in the neighbourhood as "Rippon Tors."

Next to these evidences of weather action (which are perhaps the most noticeable because they often stand out sharply against the sky) is the débris which may be seen on most hill and mountain sides. We know that, for the most part, this talus must have accumulated since the close of the Glacial period. There is scarcely a hilly slope which is not covered with blocks that have been loosened and fallen down to where we now see them. The larger of these blocks after they have fallen undergo weather-action in the places we see them occupying, and are there further subdivided, until eventually they are reduced. to unnoticeable fragments. The surface of the hill on the left-hand side as we descend Kirkstone Pass towards Brothers-water is literally covered with huge fragments of rock, one of them so large that on account of its resemblance to a simple chapel, or kirk, it has given its name to the pass. Thereabouts, these boulders (as they are mis-named, for they are mostly detached weathered fragments from the crests above)