826 • DESCRIPTIVE GEOLOGY. 



mulation of siliceous sinter, the deposit of the evaporated spring- water. Eun- 

 ning- lengthwise with this deposit are a number of parallel fissures or open seams 

 from two inches up to one foot in width, having a general trend of north 8 ° west. 

 These fissures are generally continuous, though sometimes filled at intervals 

 with debris that has fallen in and choked up the passage. All along the 

 length of these fissures are seen jets and clouds of steam rising, and the sound 

 of water boiling violently may be heard at short distances below the surface, 

 although concealed from view. Where the fissure is perpendicular, a depth 

 of 10 or 15 feet may be seen, and in some instances water is at the bottom. 

 In several places, the steam issues in puffs, with a noise like that from a 

 steam-boiler, and jets of hot water are thrown up, with more or less force, 

 frequently 10 and 20 feet in height, while in other places the water is raised 

 Avith just sufficient force to bubble up above the surface and run off. In 

 the whole area, there are but one or two small basins where water is at all 

 times standing. In several places, there are elevated conical mounds built 

 up by the sinter deposited from the boiling waters. The water flowing from 

 these sources runs away partly over the surface of the deposit and partly 

 through channels concealed from view a short distance below the surface, 

 and probably finds its way to the Truckee River. The sediment, or rather 

 deposit, from these waters is quite friable, and lies in thin strata; it is occa- 

 sionally porous and cellular, almost resembling coral. Sulphur occurs coat- 

 ing the other portions of the deposit. The steam also emits the odor of 

 sulphurous gas. 



An analysis of this siliceous sinter has been made by Mr. R. W. Wood- 

 ward, who reports the following composition : 



Silica 92.67 92.76 



Alumina and ferric oxide 0.80 . 0.65 



Lime 0.14 0.18 



Magnesia 0.05 0.05 



Soda.. : 0.75 0.99 



Potassa 0.18 0.15 



Loss by ignition 5.45 5.47 



100.04 100.25 



