476 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



the base of the ridge. These springs are, from the color of their depos- 

 its, known as the Violet Springs, and the branch which they supply 

 with water is known as Violet Creek. 



A short distance above the mouth of Alum and Sour Creeks, which 

 join the Yellowstone very close together, are the Crater Hills, on and 

 about which are very fine hot sulj^hur springs, while all about, covering 

 several square miles, the country is encrusted with their deposits. 



About a mile above the Upper Fall the river breaks into rapids, then 

 into a succession of lively cascades before rushing over the cliif at the 

 Upper Pall. At the crest of the fall the river is contracted to a width 

 of about 80 feet, and is shot out to a considerable distance, so that in 

 all probability there is an abundance of room to pass under the fall. 



The Lower Fall is about half a mile below the Upper, the current 

 of the river between them being quite rapid. At the brink the river is 

 100 feet wide, with an unknown depth. I shall not burden the reader 

 with an extended description of these falls, which have been amply il- 

 lustrated by the reports of others. 



This year I was enabled to make careful, direct measurements of them 

 by means of cords, and have obtained results which may be depended 

 upon. The Upper Fall was measured by dropping a weighted line from 

 the top of the overhanging clift" immediately adjoining the fall, to the 

 level of the water at its base, thus obtainiug as correct a measurement as 

 could be desired. This measurement gave 112 feet as the clear height 

 of the fall.* This result, as compared, with the height (140 feet) which 

 I obtained in 1872 from barometric measurement, simply gives another 

 illustration of the uncertainty attending such work, even when made 

 under the most favorable circumstances. In this and in other similar 

 cases, the fact that the height as measured by barometer is greater than 

 the true height, it seems to me, may be explained by the downward rush 

 of air at the lower station, which, of course, would produce an abnor- 

 mal pressure at that point. 



My measurement of the Lower Fall was not as simple in method, and 

 allows more room for error than in the case of the Upper Fall. I found 

 a point, by means of the clinometer, on the eastern wall of the canon 

 and very near the fall, at the same level as its top. Thence I stretched, 

 the line down the caiion wall to the level of the foot of the fall, reach- 

 ing it at a point so close that we received a thorough drenching from 

 the spray. Then, with a clinometer, I measured as accurately as possi- 

 ble the angle of inclination of the line. This gave as the height 297 

 feet. Though this result cannot be regarded as strictly accurate, still 

 its error must be small; and in round numbers, 300 feet may be re- 

 garded as a close approximation to the true height. Ludlow measured 

 this fall directly by means of a sounding line, obtaining 310 feet as the 

 height, a result agreeing quite closely with mine, especially when one 

 reflects on the difficulty of determining when the weight was at the 

 base of the fall, in the cloud of mist and the rushing river. Most of the 

 other measurements are barometric. Such was that of Captain Jones, 

 who gave a height of 328.7 feet. 



The measurement made by Mr. iST. P. Langford in 1870, and first pub- 

 lished in the rei)ort of Lieutenant Doane, gave a height of 350 feet to 

 this fall. It was made with a line stretched on an incline, but there was 

 no way of measuring with any approach to accuracy the angle of the 



* Captain Jones, in 1873, by barometric measurement, found this fall 150.2 feet high; 

 "wbile Lieutenant Doane, in 1870, by a line, found a lieigbt of 115 feet; and Ludlow, 

 by the same method, 110 feet; the last two of which agree very closely with my own. 



