GEOLOGICAL SURVEY OF THE TERRITORIES. 151 



pearance of the ci"ater when fhe water has receded into the tube. A few 

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

 timber, there is a group of quiet sp*i'iugs, ranging in temperature from 100° 

 F. to 190° F., the average being 171°.3 F. A number of them are mud- 

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

 sulph"(ir. The analysis of a specimen of blue clay from one of these 

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



Per cent 



Loss by ignition 15. 15 



Silica 50.70 



Alumina 20. 27 



Ferric oxide 3. &j 



Magnesia 11. 55 



Lime Trace. 



Sulphuric acid Trace. 



Chlorine Trace. 



100. 92 



Grand Geyser is 460 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 geyser-tube, measuring 4 

 feet by 2 feet. The depth w^as not ascertained. All the eruptions 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 cami^ed 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 : 



Firsf 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. — G.33 a. m., eruption began ; 6.36 a. m., 

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

 a. m., eruption began again ; 6.46 a. m., eruption suspended ; maximum 

 height, 173 feet; mean, 149 feet. 6.56 a. m., action recommenced. 7.5 

 a. m., eruption ended; maximum height, 84 feet; mean, 53 feet. 



As is shown above the eruption consists of three distinct periods of 

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

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

 the tube of the Grand. The water 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 

 tapering 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 must 

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

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

 21 minutes. During the third eruption there were at first 73 pulsations 

 per minute, which afterward were reduced to 71. 



Turban Geyser. — Although this is one of the minor geysers of the upper 

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

 Sf)outs very frequently, but as all our time was occupied with the more 

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



