486 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



its course between the mouths of these two streams the Firehole has a 

 very rapid current over a bottom broken by immense bowlders, and in 

 one place makes a very fine fall of 60 feet in height. 



As was said above, Gibbon Eiver heads in the heavily-timbered, 

 marshy plateaus opposite the heads of the southern branches of the 

 Middle and East Forks of Gardiner's Eiver. The region in which these 

 streams head seems to consist of a succession of broad ridges, trending 

 north and south, and of narrow valleys, in which there are in many 

 cases, low divides, from either side of which a stream flows, one to Gar- 

 diner's, the other to Gibbon Eiver. In this way nearly all the larger 

 branches of these streams are connected. 



The valleys of these branches are mainly open and very marshy. 

 The streams have but little fall. The two upper branches flow at first 

 toward one another, the one northward, the other southward, in the 

 same valley, meeting near its middle. Then the stream turns to the 

 west and flows in that direction for 2 or 3 miles, receiving a branch 

 from the north, then turns nearly south on entering a large, open meadow, 

 and there receives a second large branch from the north. Crossing the 

 meadow it enters a close canon, by which it cuts througb a high ridge 

 which has limited its drainage basin on the south. In this canon it has 

 a very rapid current, and at its end it leaps over a fall of about 80 feet. 

 Kear this point it turns to a western course and flows thence to its 

 mouth in a narrow valley, with the high ridge above mentioned, rising 

 to a height of 1,500 feet on the right, and the hills separating it from 

 East Fork on the left. The point of junction of the streams has an ele- 

 vation of 6,872 feet. Below this point the stream is known as Madison 

 Eiver. 



The wall which has accompanied the Firehole on the west, with great 

 persistence, aud which has grown steadily higher as the stream-level 

 lias declined, develops here into a clift" 1,500 or 1,800 feet in height. 

 The ridge on the right, too, approaches the river and becomes precipi- 

 tous. The river isfchus closely confined between two rocky walls form- 

 ing its upper canon. This, though close and rocky, is not difficult to 

 traverse. It extends about 8 miles down the river from the mouth of 

 the Gibbon, when it terminates abruptly, and the river flows on in its 

 westward course down a broad, timbered valley. 



The region lying west of the Firehole has, in general, the form of an 

 elevated plateau from 8,000 to 9,000 feet above the sea, densely tim- 

 bered, cut by numerous canons, and yet containing very little water. 

 It is floored with volcanic rock, and, as is commonly the case, the 

 streams quickly find their way down beneath the surface, where they 

 flow, finally emerging at the base of cliff's in the form of huge springs. 



CLIMATE. 



This region has a climate essentially its own, differing markedly in 

 many respects from that of any other part of the West. Its atmosphere 

 is moister, its rainfall greater, its mean annual temperature lower than 

 of any other extensive portion of that region, and reciprocally it is 

 better clothed with vegetation, especially with large timber. The for- 

 est-covered areas have been indicated in the above description of the 

 topography. It may be added that of the area of the Park — 3,312 square 

 miles — no less than 2,751 square miles, or 83 per cent., are covered with 

 dense forests. This region, with the adjacent parts of Idaho and Wyo- 

 ming, contains the most heavily -timbered area in the West, with the 

 exception of parts of Oregon and Washington Territory lying west of 

 the Cascade Eange. These conditions of temperature, moisture, and 

 vegetation will be easily understood when one takes into account the 



