GEOLOGICAL SUEVEY OF THE TEREITOEIES. 151 



pearance of tlie crater wlieu fhe water has receded into the tube. A few 

 huudred yards south of the Castle, separated from it by a small belt of 

 timber, there is a group of quiet spriugs, ranging in temperature from 100^ 

 F. to 19(3° F., the average being 1710.3 F. A number of them are mud- 

 springs, and it is the only place in the upper basin where 1 noticed any 

 sulphnr. The analysis of a specimen of blue clay from one of these 

 springs, by Dr. Endlich, gives the following result : 



' Per cent 



Loss by iyuitioii 15. 15 



Silica 50. 70 



Aluniina 20. 27 



Ferric oxide 3. I<>5 



Jlaj^iiesia 11. 55 



Lime ! Trace. 



Snliilinric acid Trace. 



Chlorine Trace. 



100. 92 



Grand Geyser is 4G0 yards from the Castle, across the river. It is 

 situated at the base of a small hill, and, unlike the majority of the gey- 

 sers, has no raised cone, but only a basin sunk below the general level. 

 One would scarcely take it to be an important geyser, unless he wit- 

 nessed one of its eruptions. The basin is 52 feet in diameter and 1 foot 

 in depth. In the center is the mouth of the geysertube, measuring 4 

 feet by 2 feet. The depth was not ascertained. All the eruj)tions we 

 saw took place early in the morning, and we were unable to get the 

 height of but one, and in order to do this we camped immediately in 

 front of it and kept guard by turns through the night. It did not 

 spout, however, until daylight, but we succeeded in ascertaining the 

 exact height of the column. The eruptions are as follows : 



First eruption, August 18. — 5.20 a. m., eruption began; 5.35 a. m., 

 eruption ended. 



Second eruption, August 19. — 3.35 a. m., eruption began ; 4.12 a. m., 

 eruption ended. 



Third eruption, August 20. — 6.33 a. m., eruption began ; 6.36 a. m., 

 eruption suspended; maximum height, 122 feet; mean, 79 feet. 6.42 

 a. m., eru])tion began again ; 6.46 a. m., eruption suspended ; maximum 

 height, 173 feet; mean, 149 feet. G.oii a. m., action recommenced. 7.5 

 a. m., erui)tion euded ; maximum height, 84 feet ; mean, 53 feet. 



As is shovrn above the eruption consists of three distinct j)eriods of 

 action, fitter each one of which the water sank completely out of sight, 

 and water overtlowed from the Turban, which is in close proximity, into 

 the tube of the Grand. The ^Yater during the eruption is carried up 

 in a succession of jets, the main mass of water being large. Through 

 this a column will shoot at intervals to the greatest height. The shape 

 of the entire column is, therefore, pyramidal, broad at the base and 

 ta])ering to a point. Immense clouds of steam accompany the water, 

 and the latter in falling back shakes the ground. The third eruption 

 ■was not as high as some that were not measured. The height nuist 

 sometimes exceed 200 feet. The interval between the tirst and second 

 eruptions was 22 hours, and between the second and third 26 hours and 

 21 minutes. ])uring the third eruption there were at hrst 73 pulsations 

 per minute, which afterward were reduced to 71. 



Turbo )i Geyser. — Although this is one of the minor geysers of the upper 

 basin, it has, perhaps, one of the most uniquely beautiful craters. It 

 spouts very frequently, but as all our time was occupied with the more 

 iinportaut ones, we ascertained the height of but one eruption and 



