HAVALLAH RANGE. 687 



somewhat resembling the beds of infusorial silica, but more or less argilla- 

 ceous, yielding, when subjected to chemical analysis, a considerable amount 

 of alumina, which is undoubtedly derived from the decomposition of the 

 feldspathic groundmass of trachytes and rhyolites. They have a grayisli- 

 white color, stained bright red by ferric oxide in patches, or else in parallel 

 bands or cloudings, which develop a tendency to concentric structure. 

 None of these rocks "when treated with dilute acids gave any indication of 

 the presence of carbonate of lime. The average dip of the strata is 18° 

 to 20° to the eastward. 



There is another small outburst of rhyolite occurring as low^ broken 

 hills along the western foot-hills of the range, two or three miles south of 

 Bardmass Pass, which scarcely differs from those already described at 

 the northern end of the range, but derives some interest from the group of 

 thermal springs found near their base. The water flows out from the rock 

 on gently sloping ground along the edge of the Quaternary valley, and 

 about one-quarter of a mile east of the first prominent ridge. There are 

 between twenty and thirty circular pools of water, varying from 1 to 12 

 feet in diameter, scattered over an area of several acres, and generally 

 surrounded by a luxuriant growth of alkaline grasses. The brilliant green 

 of the vegetation, with isolated patches of bare light-colored rock, 

 together with clouds of vapor rising from the water, make the locality 

 a prominent landmark for long distances. The waters from all the pools 

 were remarkably clear, and when cold quite palatable, with a slight taste 

 of sulphur. Thermometric observations made in the open pools of four 

 springs indicated temperatures varying from 155° to 181°. But little min- 

 eral deposit was observed coating the walls of the springs, and what there 

 is consists mainly of carbonate of lime, an analysis of which, made by Mr. 

 E,. W. Woodward, gave as follows: 



Alumina 0.26 



Lime 48.32 



Magnesia 3.98 



Carbonic acid 39.07 



Insoluble residue 8.70 



100.33 



