GRANITE RANGE. 799 



This analysis bears a close resemblance to that of the Pah-tson Mount- 

 ain granite, a resemblance which is equally well shown in the lithological 

 characters of the two rocks. 



East of Granite Creek, at the base of the range, occurs an outburst of 

 basalt, rising but a few hundred feet above the desert. It forms smooth, 

 rounded hills of black, compact rock, closely resembling in its geological 

 occurrence the basaltic eruptions flanking the granite bodies of the Truckee 

 and Lake Eanges. 



About 3 miles southwest from Granite Creek Station, and near the 

 southern end of the range, is a group of hot springs known as the Granite 

 Creek Boiling or Mud Springs. Scattered over an area roughly estimated 

 at 75 acres are a large number of pools, mostly circular, varying in size 

 from 1 up to 25 feet in diameter, and surrounded by a luxuriant 

 growth of brilliant green alkaline grasses, in marked contrast to the dull 

 monotonous colors of the desert. The waters are clear and quite palatable 

 when cool. The largest one visited had a temperature of 194° in the broad 

 open pool; others indicated temperatures from 188° up to the boiling- 

 point, and yielded large volumes of vapor that could be seen many miles 

 across the desert. Along with these springs are a number of mud springs, 

 or, as they are called, "Mud Volcanoes", round basins from 2 to 3 feet 

 below the surface of the ground and varying from 6 inches to 6 feet in 

 diameter. These were filled with mud and slime, the contents being thrown 

 up and violently agitated at regular intervals, accompanied by puffs of 

 steam. Several of these springs had built up cones of hardened mud, and 

 all, with one exception, closed at the top. In this one, the aperture was 

 about 2 inches in width, and emitted a very perceptible odor of sulphuretted 

 hydrogen; it is said occasionally to throw out mud and water in all direc- 

 tions for a distance of 100 yards. Fragments of this ejected material were 

 found by analysis to have the composition of clay. 



From the base of the Granite Range westward, and west of the lesser 

 Mud Lake, extends a broad plateau country made up exclusively of extensive 

 flows of basalt, known as the Madelin Mesa, or Madelin Plain. It possesses 

 the peculiar topography of the regions generally known in the West as 

 lava beds, being cut through by deep, nan-ow, intricately branching ravines, 



