is a broad field, situated on the table-land, which in comparatively small compass contains some of the most interesting subjects for the geologist which are to be found in this country or the world. The entire tract is a fossil forest. Its trees, to be sure, are leveled with the ground; but their stumps and many of their prostrate trunks remain in a condition of stony metamorphosis which may challenge the Enchanted Groves of fairy lore and the Arabic legend of Aladdin's ruby fruit. Nothing can exceed the perfection with which the original vegetable characteristics have been retained in the petrified remains. Some of the trunks, full ten feet in length, have become so thoroughly infiltrated with silicates (chiefly of aluminum, having iron for their tinge), that at first sight they look more like exquisite imitations of trees in jasper, agate, or chalcedony, than the metamorphosed bodies of trees themselves. The translation from ligneous to stony substance has been so gradual, yet so perfect, that you are reminded of the famous jack-knife which retained its identity with a new blade and a new handle. Probably nothing does in reality exist of these trees' original tissue; but each portion of that tissue survived just long enough to act as a mould, and determine every faintest marking on the flinty jelly whose consolidated mass substituted it. The result is that we have in silicates of aluminum and iron as perfect a representation as could be given by original vegetable matter, of cotton-woods, firs, and pines, throughout all the sizes attained by those growths. Nothing among mineral treasures can exceed the beauty of some specimens we found here. Looking at the cross section of one of the stone saplings, the merest tyro saw at a glance the history of its growth,

and the position which it had occupied in the arboreal scale, whether it was an ordinary exogenous tree or a conifer,-and often, too, the age at which it became stone-enchanted. Its pores, its medullary rays, its pith, its rings of growth, and, in some cases, its outer bark, were preserved as distinctly as they were the last day it budded; and though it possessed the lustrous flinty fracture common to the semiprecious stones, across the sharp edges, faithful to its original direction, ran the old grain of the wood as plain as ever. I think it was here that I felt, for the first time in my life, the sensation of avarice, and at the same time realized the sternness of that double test of values, portability, convertibility. It hurt me to go away, and leave that fieldful of gems,-tenfold more interesting to me than if they had been diamonds, simply because I had no means of transporting so much as one poor cart-load of the finest to a place where they would give all the delight, win all the admiration, of which they are capable. Of course their beauty is greatest to a mineralogist; but they possess a beauty of marking and color quite apart from this, being intrinsically among the handsomest specimens of the agate and allied stones which I ever saw in cabinet or show-case.

It is somewhat difficult to account for this curious metamorphosis upon any of the commonly received theories of petrifaction. The stumps are evidently in situ; so they cannot have been thrown up by any natural convulsion from a lower stratum, where they had been embedded and fossilized. To imagine them petrified by long submersion in a flood highly charged with silicates, is only to make another difficulty; for in that case what has become of the detritus which

should surround them, and why did these exceptional phenomena occur here when the lower ground, which must have been simultaneously under water, exhibits no trace of similar operations? The most probable hypothesis may be that the whole tract was once cov ered with strongly silicated springs, and that as fast as death deprived a tree of its elaborating and selective apparatus, it became a mere mechanically acting bundle of capillaries, and sucked up the liquor of immortality, which made it a gem. I succeeded in bringing away but a few specimens. They are small, but among the most exquisite for color, lustre, and reproduction of the original tissue. They vary through every shade of purple, brown, yellow, red, and white; and almost any chance specimen that might be collected, would cut into an elegant ornament for the toilet or writing-table, for seal-ring or sleeve-buttons, of the kind for which blood-stone or onyx is usually employed.

Thirty miles from Denver, on a table-land of the divide, we came to a peculiar hill of the butte kind, a single cone, rising abrupt and solitary out of the level plain to the height of about four hundred feet, and crowned with a rude cube of red argillaceous sandstone, nearly five hundred feet in circumference and a hundred feet in altitude. Vasquez, a Spanish guide in Pike's Expedition, gave it the name of "Castle Rock," or rather the no-name, since new settlers are not sufficiently in communication with each other to be bothered about originality, and have illustrated the proverbial coincidence of great minds by fastening this appellation on every one of the multitudinous castellated formations between the tertiary clay of the Platte region and the granite mountains of the

Pacific. Still, at a distance, this Castle Rock belies. the title as little as any of its namesakes.

Accompanied by one of the gentlemen of my own party, I climbed to the very summit, while the ambulance halted for us below. We found the immense stone which formed the capital of the cone bare of soil and vegetation, save in crevices. On all sides it overhung the earth mound on which it rested to the distance of several feet, thus getting a look of being poised upon its centre, just insecure enough to increase its picturesque effect. By insinuating ourselves into fissures and making bold use of projecting knobs, we contrived to work our way around its sides to the upper surface. Here we found a fine breezy platform, perfectly level, and commanding a view in every direction, which amply repaid our trouble. Here and there through the gray Plains we could see a flock of antelope feeding quietly; one side of our pedestal was alive with screaming hawks, who built their colony of nests there, nowise counting on intrusion from such visitors as we; we could see the little hares playing below us in the ashen furze which thatched the cone; and we could have tossed a stone on the roof of the ambulance, dwindled to a speck, where it stood awaiting us at the foot of the butte. The declining sun was bathing the great brown mountains in an amber glow; and still, far off to the west and southerly, Old Pike was baring his giant forehead of white and crystal, through a gap in our nearer ranges, to the common splendor. It was the quietest, sunniest, most satisfying mount of vision we had yet climbed. We came down to find that the enterprising buckboard had come up with our ambulance, stopped to put Castle Rock in our artist's sketch-book, and pre

ceded us in the direction of Pike's Peak and supper. We hurried on after it, and about nightfall came to a comfortable log-house, situated near the head of Plum Creek, here a mountain brook of considerable size, and not far from the junction of the divide on which we had been travelling with that which separates between the affluents of the Platte and of the Arkansas. The house is a neat structure of sawed timber, all of it got out in a steam saw-mill, imported by the proprietor, a man named Sprague, who, like Richardson, increases the income of a ranchman by the entertainment of pilgrims such as we. Here we had an excellent supper; and when we discovered that there were not enough beds to go round, those who were left out camped cheerily down on their blankets, and all slept equally well till sunrise.

We had now reached the grand divide between the Platte and the Arkansas. It seemed rather a spur from the mountains than one of their attendant foothills. Immediately about Sprague's the scenery was wildly rocky. The house stood at the foot of a magnificent gray crag, seven hundred feet high, densely wooded with evergreen along a series of gulches which channeled its face at angles that nearly made climbing impossible. Plum Creek was quite embowered in the willows and willow-leaved cottonwoods, which belong to the never-failing water-courses of the Rocky range. The valley through which it flowed was as green as a June meadow in the East; and the sweet, pure air was of itself enough to tell us that we had risen far above the level of Denver.

We left Sprague's early in the morning, well satisfied with his accommodations, and glad to have found, so deep in these solitudes a man who had evidently