It is difficult, when contemplating the present appearance and situation of these rocks, to prevent the {189} imagination from wandering back to that remote period, when the billows of an ocean lashed the base of the Andes, depositing, during a succession of ages, that vast accumulation of rounded fragments of rocks, alternating with beds of animal remains, which now extends without interruption from the base of this range to the summits of the Alleghany mountains; and endeavouring to form some idea of that great subsequent catastrophe, by which this secondary formation has so changed its elevation, in relation to the primitive, that its margin has been broken off and thrown into an inclined or vertical position. The valley which intervenes between this huge parapet of sand-rock and the first range of the primitive is nearly a mile in width; it is ornamented with numerous insulated columnar rocks, sometimes of a snowy whiteness, standing like pyramids and obelisks, interspersed among mounds and hillocks, which seem to have resulted from the disintegration of similar masses. This range of sandstone would appear to have been originally of uniform elevation and uninterrupted continuity, running along the base of the mountains from north to south; but it has been cut through by the bed of the Platte, and all the larger streams in their descent to the plains. From our camp, we had expected to be able to ascend the most distant summits then in sight, and return the same evening; but night overtook us, and we found ourselves scarcely arrived at the base of the mountain.[140] The lower part of the sandstone stratum, being exposed at the western declivities of the hills, and in the parts nearest the granite, contains extensive beds of coarse conglomeratic, or pudding-stone, often of a reddish colour. The more compact parts of the rock contain the remains of terebratulæ, and other submarine animals. Among these, few are entire or in good preservation. We observed here several singular scorpion-like, spider-formed {190} animals, inhabiting under stones and dried bisons' dung. They have a formidable appearance, and run actively. They belong to the class arachnoides, genus galeodes, which has been heretofore observed only in warm climates; not one was known to inhabit this continent.[141] [140] The deceptiveness of Colorado distances, owing to the rarefied atmosphere, is one of the commonest observations of tourists. Pike, in 1806, thought it would be possible to ascend the peak which now bears his name, and return to camp in the course of one day. From Colorado Springs it is apparently only a short walk to the summit; but the air-line distance is twelve miles, and that which must actually be travelled is two and a half times as great.—ED. [141] Genus _Galeodes_, OLIV.—1. G. _pallipes_, SAY.—Hairy, mandibles horizontal, fingers regularly arquated, abdomen sub-depressed livid.