of uplifts, operating at as many periods of disturbance: one, which we may call the primary, elevating the axial ranges of the Continent, whose principal trend is north and south; and the other, which we may call the secondary, operating subsequently between the parallel lines of the first uplift, with a general trend at right angles to it. The first upheaval produced a mountain region about six hundred miles wide at its widest part, with lofty valleys between its highest ranges. The second barred these valleys at intervals, turning them into the present plateaus or basins, and completing the link formation which we now see.

Though not entirely limited in its occurrence to the Rocky Mountains, this formation is strikingly characteristic of that system, and is nowhere else so constant a trait both of scenery and geology. Upon its existence depend the most important results to the future settlement of the interior. Wherever these transverse bars occur, it will instantly appear that the ease of irrigating the levels between the axial ranges is vastly enhanced. Many of them rise to a height as great as that of the longitudinal ranges; some of them are higher than those in their immediate neighborhood. They condense the moisture of the upper atmosphere currents, turn it into snow, and thus become reservoirs of irrigation-storehouses of fertility for the included levels below.

Any good map constructed after the latest surveys, but the maps of the War Department especially, will exhibit the link formation with peculiar clearness in many different portions of the range, but in none more strikingly than in the tract lying between 38° and 41° lat. N. and 105° and 107° lon. W. Within these boundaries lie three great links, whose interior

basins possess a fertility of soil, a grandeur and beauty of scenery, and a loveliness of climate which fascinated explorers long before the discovery of the precious metals allured them to the interior of the Continent, and which now cause them to be better known than almost any part of the Rocky Mountain system, save that in the immediate vicinity of mines. These go by the titles of the North, Middle, and South Parks. Their isolation from each other is almost complete; the transverse ridge dividing the Middle from the South Park being quite impenetrable, while a water-shed of gentler ascent and more broken lines separate the former from the North Park. The resemblance which these formations bear to the links of a chain strike one instantly on looking at the map. Not less striking is the amount of water shed into each of the inclosed basins from the snow-ridges which form its rim. The amount furnished by direct rain-falls is inconsiderable, - during some years almost literally nothing, and may be left out of the calculation. North Park will be observed to possess a system of irrigation so complete and so bountiful that art could scarcely improve it. Innumerable tributaries, shed from its walls in every direction, unite to make the North Fork of Platte, which was separated from us as we crossed Laramie Plains only by the single range of black hills on our left, and which, after flowing around the base of that grand mesa on which the Laramie Plains lie, makes another grand detour, and reaches the Great Plain at Fort Laramie, a degree further north than where we left them. Another system of tributaries combines to the southerly, and sheds itself through a break in the southwest corner of the link, under the name of the

Blue River - contributing one important affluent to that mysterious stream which, after traversing one of the least known and most savage regions of the world, finally empties itself into the Gulf of California under the title of the Colorado River. A short inspection of the hydrography of this region will show us that the true division between the North and Middle Parks occurs in the line of the watershed between the tributaries of the North Platte and those of the Blue. The latter river, it will also appear, receives the entire drainage of the Middle Park -an amount of water almost wholly derived from the snow-meltings of the tremendous ranges inclosing the park, yet equal to that of any tract of corresponding area under the moist sky of our Atlantic slope. The South Park gives birth to the South Platte and the Arkansas- both unfailing streams, though they receive no affluents of any size within a hundred miles of their source. The Cache la Poudre (through whose pass, it will be recollected, we ascended to the Laramie Plateau) is the first tributary of noticeable volume belonging to the South Platte; yet the latter stream is an abundant and rapid river long before it receives this increment, indeed in the immediate neighborhood of Denver.

Still further to the north than the Parks lie two examples of the link formation in Laramie Plains and the plateau of the Great South Pass. I have indicated, as it occurred in the order of our itinerary, the longitudinal and transverse ranges which environ the former. North of the Wind River Mountains, the transverse range which forms its lower boundary, lies an irregular plateau to which the South Pass furnishes its main western exit, of much vaster ex

tent than those we have been considering, yet belonging equally with them to the link system. Within this link rise the Snake Fork of the Columbia (or, as we may properly say, the Columbia itself, the Snake deserving the honor of consideration as the main stream), the Yellowstone, and the Missouri. This link is the Delphi of our Continent's physical geography, the oupaλos yns, since from it, as a nodal tract, ομφαλος γης, flow the two chief streams of North America, the one sending its waters to the Gulf of Mexico, the other emptying into the North Pacific Ocean; their cradling fountains separated from each other by a narrow ridge, and their graves in the all-swallowing sea distant from each other 2,225 miles in an air line.

The link formation is exhibited everywhere in the Rocky Mountains. It is not only the type on which has been constructed every great tract of plateau or basin country like those just considered, but the traveller is constantly finding it repeated on a smaller or even a miniature scale. Thus, the famous goldleads of Colorado lie environed on the north and south sides by walls belonging to the transverse system of uplifts; their west boundary is the giant wall of the Middle Park itself; from the west side of this wall flows a tributary to the Blue River, the Colorado, and the Gulf of California; from its eastern face comes Clear Creek, the famous stream that, after supplying the mines, runs to the Platte, and finally reaches the Gulf of Mexico: the springs of the two streams are divided by a single snow bank. "Ogden's Hole" is a tract lying in similar environment among uplifts of the Wahsatch, differing so much between themselves in point of geological period, that immediately adjoining the granite and sandstone of the main

range are found much disturbed strata of the carboniferous series, which may become of immense value when the Pacific Railroad, with its locomotives, its machine-shops, and the increase of population following in its wake, shall demand and justify the development of Utah's internal resources.

In the mutual relations of the longitudinal and transverse systems of uplift lies a field of study no less important than interesting. Their relative ages; their conterminous points, or, where such cannot be made out, their tracts of transition into each other; the facts as to the existence of the precious metals in both or in one only, and if the latter, then in which one, these are merely passing hints for a line of investigation which cannot fail to be fruitful of most valuable results.

This episode upon the link formation has its close connection with our itinerary, though I seemed to wander away from it just after leaving Sulphur Springs.

Descending from the water-shed, we had emerged through the magnificent gallery of Bridger's Pass into a tract which forms another link, not until now mentioned by me as such, of the same type as all the others, and nearly the same longitudinal system as that of the South Pass plateau. From that plateau we were now divided by the Wind River Mountains, and their continuation on a smaller scale along the Sweetwater. This transverse range formed the northern segment of our link. The Uintah range, and its continuations along the line of the Yampah, formed a corresponding segment on the south. With these the Wahsatch range inosculated on the west, and on the east the parallel longitudinal range which we had