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Art. XV. The so-called Two-Ocean Pass. (Plates III,

IV.)

By F. V. Hayden.

This somewhat singular geographical feature has never yet been clearly explained, though it is noted on some of our maps as far back as 1851. It was known to the old trappers of a still earlier period, and they had a tradition of its existence. So far as I can ascertain, the first published notice of it is found in Capt. W. F. Raynolds's Report of the Exploration of the Yellowstone in 1868, page 11. Captain R. writes as follows:

"Bridger also insisted that immediately west of the point at which we made our final effort to penetrate this singular valley (Yellowstone) there is a stream of considerable size which divides and flows down either side of the water shed, thus discharging its waters into both the Atlantic and Pacific Oceans. Having seen this phenomenon on a small scale in the highlands of Maine, where a rivulet discharges a portion of its waters into the Atlantic and the remainder into the St. Lawrence, I am prepared to concede that Bridger's 'Two Ocean river' may be a verity."

Again, Captain Jones, of the United States Engineers, in his report of a Reconnaissance of Northwestern Wyoming, gives a brief description of this pass, which attracted some attention at the time:

"At this divide occurs a phenomenon, probably the one referred to by the early trappers as the 'Two Ocean Pass.' Marching at the head of the column where the trail approached the summit, I noticed that the riband of meadow, in which the stream lay we had been following, suddenly dropped away in front of us with a contrary slope. I could still see the stream threading it, and for a moment could scarcely believe my eyes. It seemed as if the stream was running up over this divide and down into the Yellowstone behind us. A hasty examination in the face of the driving storm revealed a phenomenon less startling perhaps, but still of remarkable interest. A small stream coming down from the mountains to our left I found separating its waters in the meadow where we stood, sending one portion into the stream ahead of us, and the other into the one behind us-the one following its destiny through the Snake and Columbia Rivers back to its home in the Pacific; the other, through the Yellowstone and Missouri, seeking the foreign water of the Atlantic by one of the longest voyages known to running water. On the Snake

River side of the divide the stream becomes comparatively large at once, being fed by many springs and a great deal of marsh." In figure 3, plate III, I give a copy of Captain Jones's map of this locality.

During the past season, the writer, on his return from the Yellowstone Park, passed over this divide, and made a somewhat careful study of it. The chart, which was sketched on the spot by Mr. W. H. Jackson, shows the exact character of the drainage.

This pass is located about longitude 110° 00′ and latitude 44° 05'. Atlantic Creek is a branch of the Upper Yellowstone River. The party with which the writer was connected passed up the east side of the Yellowstone Lake to the mouth of the Upper Yellowstone River, and thence up the valley of that stream about thirty miles to what may be called the Three Forks, near Bridger's Lake. The east fork bears the name of Atlantic Creek. From the Three Forks the party passed up the val ley of Atlantic Creek to the southwest, for the most part over a grassy valley, which was enclosed between vertical walls of volcanic breccia 1,000 to 1,200 feet in height. This valley is purely one of erosion. The breccia itself is of very modern age, probably of Quaternary date, and the wearing-out of this great groove must have been an exceedingly modern event. So far as can be seen from the summit of the mountains on either side, no divide can be observed. The erosion seems to have produced a gentle slope on either side of the watershed. At the summit, not over ten miles from the junction of the Atlantic Creek with the Upper Yellowstone, the elevation, 8,081 feet, is not more than 150 feet above the valley of the main stream. The valley is at first quite narrow; but it gradually expands into an open, grassy meadow, which, near the pass, becomes one-third of a mile in width, and gradually closes up again into a cañon on the Pacific slope. So obscure is the drainage that we camped the night of October 3, 1878, within a fourth of a mile of the water-divide, but did not perceive it until we commenced our march the following morning.

The conditions are as follows: The summit of the pass for a distance of about half a mile is so nearly level that a marsh is formed, which, in times of high water, becomes a small lake. A portion of the waters from the surrounding mountains accumulates in the marshy meadows, and gradually gravitates from either side into two small streams, one of which flows to the northeast, the other toward the southwest. On the east side of the divide there is a depression or gorge in the mountain, which is occupied by a small stream that at the time of our visit flowed in a well marked channel toward the northeast into Atlantic Creek. This is the well-known Two-Ocean Creek. At the base of the mountain-side (c), a small stream rises from a sink-hole, or spring, which at the time the writer saw it (October 4) was nearly dry, and but little water was running in Two-Ocean Creek (a). This spring-hole was not separated from the latter creek more than six feet, and a small dry channel connecting it with a showed that in times of high water a portion of the water that

started down the mountain-channel (a) broke over the side into the spring-hole (c), and flowed thence through channel c to the Pacific. Lower down in the Two-Ocean channel are two places, shown by dotted lines, where there are two old channels connecting in time of high water with channel c, showing that a portion of the waters that started down the mountain-side for the Atlantic was diverted toward the Pacific. On the opposite side of the pass there is a similar depression in the breccia wall, down which, at the time of the melting of the winter's snows, much water flows.

The points b and d are close together, and the waters of the grassy meadows, which lie between them, probably separate, a part taking one direction and a part the other. The little lake or marsh in the center, of course, furnishes a supply or reservoir for both. Although the simple separation of water on a divide is not an uncommon occurrence, yet the conditions observed in this case are rarely repeated, and have not before come under the writer's observation. Small lakes upon the summit of a water-divide, with drainage from either side, are not uncommon from the north line of the United States to Mexico. On the divide between the Yellowstone and Snake River drainage, we often find small lakes or reservoirs of water which in the wet season send small portions to the Atlantic and to the Pacific.

The following are examples of peculiar forms of drainage, which bear some relation to that of the "Two-Ocean Pass":

Figure 1 was observed by Mr. A. D. Wilson, of the Survey, in British Columbia, between Fort Douglass and Lillooet. From b to c via a is about 100 miles' travel. The lake at a lies on the summit of a mountain, and is fed principally by springs; its water runs either way through other lakes 25 or 30 miles long, and finally flows into Frazer River at b and c.

In Fig. 2 is given a sketch of a case where a small mountain stream divides and runs in two channels to the main creek. It occurs in the Wind River Mountains, near the source of the Popo Agie Creek, a branch of Wind River. The small stream enters a depression at a, from which its waters find their way out, partly to the right and partly to the left of the rocky hill d, and empty into the main stream at b and c. Not far from this locality is another example similar to the above, in which a mountain torrent descends against the upper end of a great slide of rock, and is broken into two nearly equal parts, and so descends to the main creek.