limestone hills, of which the rude contour is given in Fig. 17, page 154. The great slope seen on the left, rising about seven thousand feet above the ravine, is nothing but the back of one sheet of limestone, whose broken edge forms the first cliff at the top, a height of about six hundred feet, the second cliff being the edge of another bed emergent beneath it, and the slope beyond, the surface of a third. These beds of limestone all descend at a uniform inclination into the gorge, where they are snapped short off, the torrent cutting its way along the cleft, while the beds rise on the other side in a huge contorted wave, forming the ridge of mountains on the right,—a chain about seven miles in length, and from five thousand to six thousand feet in height. The actual order of the beds is seen in Fig. 18, and it is one of the boldest and clearest examples of the form of mountains being correspondent to the curves of beds which I have ever seen; it also exhibits a condition of the summits which is of constant occurrence in stratified hills, and peculiarly important as giving rise to the serrated structure, rendered classical by the Spaniards in their universal term for mountain ridges, Sierra, and obtaining for one of the most important members of the Comasque chain of Alps its well known Italian name-Il Resegone. Such mountains are not merely successions of irregular peaks, more or less resembling the edge of a much-hacked sword; they are orderly successions of teeth set in one direction, closely resembling those of a somewhat overworn saw, and nearly always produced by successive beds emerging one from beneath the other.

§ 22. In all such cases there is an infinitely greater difficulty in accounting for the forms than in explaining the fracture of a single bed. How, and when, and where, were the other portions carried away? Was each bed once continuous over a much larger space from the point where its edge is now broken off, or have such beds slipped back into some gulf behind them? It is very easy for geologists to speak generally of elevation and convulsion, but very difficult to explain what sort of convulsion it could be which passed forward from the edge of one bed to the edge of another, and broke the required portion off ehac without disturbing the rest. Try the experiment in the simplest way put half a dozen of hard captain's biscuits in a sloping

position on a table, and then try, as they lie, to break the edge of each, one by one, without disturbing the rest. At least, you will have to raise the edge before you can break it; to put your hand underneath, between it and the next biscuit, before you can get any purchase on it. What force was it that put its fingers between one bed of limestone 600 feet thick and the next beneath? If you try to break the biscuits by a blow from above, observe the necessary force of your blow, and then conceive, if you can, the sort of hammer that was required to break the 600 feet of rock through in the same way. But, also, you will, ten to one, break two biscuits at the same time. Now, in these serrated formations, two biscuits are never broken at the same time. There is no appearance of the slightest jar having taken place affecting the bed beneath. If there be, a huge cliff or gorge is formed at that spot, not a sierra. Thus, in Fig. 18, the beds are affected throughout their united body by the shock which formed the ravine at a; but they are broken, one by one, into the cliffs at b and c. Sometimes one is tempted to think that they must have been slipped back, one from off the other; but there is never any appearance of friction having taken place on their exposed surfaces; in the plurality of instances their continuance or rise from their roots in waves (see Fig. 16 above) renders the thing utterly impossible; and in the few instances which have been known of such action actually taking palce (which have always been on a small scale), the sliding bed has been torn into a thousand fragments almost as soon as it began to move.*

§ 23. And, finally, supposing a force found capable of breaking these beds in the manner required, what force was it that carried the fragments away? How were the gigantic fields of shattered marble conveyed from the ledges which were to remain. exposed? No signs of violence are found on these ledges; what marks there are, the rain and natural decay have softly traced through a long series of years. Those very time-marks may have indeed effaced mere superficial appearances of convulsion; but could they have effaced all evidence of the action of

* The Rossberg fall, compared to the convulsions which seem to have taken place in the higher Alps, is like the slip of a paving stone compared to the fall of a tower.

such floods as would have been necessary to carry bodily away the whole ruin of a block of marble leagues in length and breadth, and a quarter of a mile thick? Ponder over the intense marvellousness of this. The bed at e (Fig. 18) must first be broken through the midst of it into a sharp precipice, without at all disturbing it elsewhere; and then all of it beyond c is to be broken up, and carried perfectly away, without disturbing or wearing down the face of the cliff at c.

And yet no trace of the means by which all this was effected is left. The rock stands forth in its white and rugged mystery, as if its peak had been born out of the blue sky. The strength that raised it, and the sea that wrought upon it, have passed away, and left no sign; and we have no words wherein to describe their departure, no thoughts to form about their action, than those of the perpetual and unsatisfied interrogation,

"What ailed thee, O thou sea, that thou fleddest?

And ye mountains, that ye skipped like lambs ?"

CHAPTER XIII.

OF THE SCULPTURE OF MOUNTAINS:-SECONDLY, THE CENTRAL

PEAKS.

§ 1. IN the 20th paragraph of the last chapter, it was noticed that ordinarily the most irregular contortions or fractures of beds of rock were found in the districts of most elevated hills, the contortion or fracture thus appearing to be produced at the moment of elevation. It has also previously been stated that the hardness and crystalline structure of the material increased with the mountainous character of the ground; so that we find as almost invariably correlative, the hardness of the rock, its distortion, and its height; and, in like manner its softness, regularity of position, and lowness. Thus, the line of beds in an English range of down, composed of soft chalk which crumbles beneath the fingers, will be as low and continuous as in a of Fig. 16 (p. 151); the beds in the Jura mountains, composed of firm limestone, which needs a heavy hammer stroke to break it, will be as high and wavy as at b; and the ranges of Alps, composed of slaty crystallines, yielding only to steel wedges or to gunpowder, will be as lofty and as wild in structure as at c. Without this beneficent connection of hardness of material with height, mountain ranges either could not have existed, or would not have been habitable. In their present magnificent form, they could not have existed; and whatever their forms, the frequent falls and crumblings away, which are of little consequence in the low crags of Hastings, Dover, or Lyme, would have been fatal to the population of the valleys beneath, when they took place from heights of eight or ten thousand feet.

§ 2. But this hardening of the material would not have been sufficient, by itself, to secure the safety of the inhabitants. Unless the reader has been already familiarized with geological facts, he must surely have been struck by the prominence of