middle of a rain-mark, having been formed subsequently. Sometimes the worms have dived beneath the surface, and then reappeared. All these appearances, both of rain-prints and worm-tracks, are of great geological interest, as their exact counterparts are seen in rocks of various ages even in formations of very high antiquity.* Small cavities, often corresponding in size to those produced by rain, are also caused by air-bubbles rising up through sand or mud; but these differ in character from rain-prints, being usually deeper than they are wide, and having their sides steeper. These, indeed, are occasionally vertical, or overarching, the opening at the top being narrower than the pit below. In their mode, also, of mutual interference they are unlike rain-prints.†

In consequence of the effects of mountains in cooling currents of moist air, and causing the condensation of aqueous vapour in the manner above described (page 329) it follows that in every country, as a general rule, the more elevated regions become perpetual reservoirs of water, which descends and irrigates the lower valleys and plains. The largest quantity of water is first carried to the highest region, and made to descend by steep declivities towards the sea; so that it acquires superior velocity, and removes more soil, than it would do if the rain had been distributed over the plains and mountains equally in proportion to their relative areas. The water is also made by these means to pass over the greatest distances before it can regain the sea.

Earth-pyramids or stone-capped pillars of Botzen in the Tyrol. It is not often that the effects of the denuding action of rain can be studied separately or as distinct from those of running water. There are, however, several cases in the Alps, and especially in the Tyrol near Botzen, which present a marked exception to this rule, where columns of indurated mud, varying in height from twenty to a hundred feet, and usually capped by a single stone, have been separated by rain. from the terrace of which they once formed a part, and now stand at various levels on the steep slopes bounding narrow

* See Elements of Geology, Index

Rain-prints.

+ See Lyell on recent and fossil rains.

Quart. Journ. Geol. Soc. 1851, vol. vii.

p. 239

valleys. Botzen is situated on the Eisack, two miles abovethe junction of that river with the Adige, and is 836 feet above the sea. It is in the valleys of two tributary streams which join the Eisack a short distance above Botzen, that the principal groups of pillars occur. Those nearest to the town and situated about a mile and a half to the N.E. of it, are in the ravine of the Katzenbach, elevated about 1,700. feet above Botzen; they are the most remarkable of any for their number, size, and beauty. The other pillars occur in the ravine of the Finsterbach, near Klobenstein, at the height of about 2,200 feet above Botzen, and three and a half miles N.E. of that town. These I shall describe more particularly, as Sir John F. W. Herschel has had the kindness to enable me to give an accurate representation of them drawn by himself in 1824, by the aid of the Camera Lucida. I have not room to give his entire drawing, but have selected a part of it, representing the entrance of a tributary ravine into the main valley. (See Plate II.). In such smaller ravines, the same features which are seen on the boundary cliffs of the main valley are repeated, with no other difference than the diminished distance which separates the opposite banks, and the lesser size and number of the columns stretching from the top of each bank down to the brook which flows at the bottom. The breadth of the valley of the Finsterbach is between 600 and 700 feet, and its depth from 400 to 500. The pillars are many hundreds in number, and the precipitous banks from which they spring slope at angles of from 32° to 45° degrees. The lower part of each column has usually several flat sides, so that it assumes a pyramidal instead of a conical shape. The columns consist of red unstratified mud, with pebbles and angular pieces of stone, large and small, irregularly dispersed through them. The whole mass, in short, out of which they are shaped answers in character to the moraine of a glacier, and some of the included fragments of rock have one or more of their faces smoothed or polished, furrowed and scratched, in a manner which clearly indicates their glacial origin. The stones have not their longer axes arranged in one direction, as would be the case if they had been deposited by running

water. The matrix of hard mud has been derived evidently from the decomposition of the red porphyry, of which the whole of this country is made up, and the most numerous and largest of the capping-stones consist of the same porphyry; but blocks of granite, two or three feet in diameter, which must have come from a great distance, as well as boulders of a hard chlorite rock equally foreign to the immediate neighbourhood, are also scattered sparingly through the reddish matrix. The Finsterbach, besides cutting through this unstratified mass, has excavated its channel for a depth of several yards through the underlying porphyry, or at one point through a sandstone of the Lower Trias which occasionally appears in this region. The series of geological events of which we have evidence both in this ravine and in that of the Katzenbach, will be better understood by reference to the diagram, fig. 17. First a valley a b c was excavated in a country consisting almost entirely of red porphyry. Secondly, this original valley was filled up in its lower part by Fig. 17.

Red Porphyry

Diagram illustrative of the Formation of Earth-pillars.

abc. Outline of original valley hollowed out of porphyry.
dbed. Moraine left by glacier as it receded up the valley.

f. Chasm cut by torrent through the moraine before the first earth-
pillars were formed.

bi. Channel of torrent excavated in porphyry below the level of

the original valley.

gih. Outline of the present valley, the earth-pillars marked by dark
lines being still standing. The faint outlines between g and h
represent portions of earth-pillars and their capping-stones
now destroyed.

moraine matter, d be d, probably left by a large glacier as it retreated up the valley at the close of the Glacial Period.