36 BULLETIX 54, XT. S. DEPAETMEXT OF AGEICLtlTUEE. 



tion eastward into the Railroad Valley proper. At its northern extremity the Rail- 

 road Valley proper is limited by an alluvial divide across the narrow Newark Valley; 

 but this divide, though superficially alluvial, is really due to the general uplift of 

 this region and is unquestionably pre-Lahontan. The southern extremity of the Rail- 

 road Valley is determined by the eastward bend of the Quinn Canyon I^Iountains 

 (\Miite Pine Range) to join the Reveille Range, which is the southward extension 

 of the Pancakes. It is probable that the Penoyer Valley, lying south of this divide, 

 was once a tributary of the Railroad Valley, but this will be discussed below. 



The present deepest depression of the Railroad "\'alley lies rather north of its center 

 and is a typical playa about 80 square miles in area and not unusually saline. South 

 of this are a large number of smaller playas determined by recent alluvial divides 

 and receiving the di-ainage of their immediate sui'roundings only. One of these, 

 lying south of the Twin Springs Pass, is of considerable size and is separated from the 

 main valley by a fairly high divide due mainly to the fan built eastward by the Hot 

 Creek A'alley discharge as it leaves the Twin Springs Pass. This divide may be of 

 considerable antiquity and the basin behind it may have had a significant independent 

 history. It is, however, the writer's opinion that both divide and basin are post- 

 Lahontan. Some of these southern playas are of considerable salinity and about 

 the north end of the main playa are a number of small pans apparently caused by 

 previous dune accumulations and which are also quite saline. The salts of some of 

 these pans contain significant proportions of potassium and the Railroad Valley 

 Company of Tonopah is now (1912) drilling at the north end of the main playa in the 

 hope of finding bm-ied deposits of potassium salts. 



Hot Creek Valley and its tributaries have suffered less from alluvial damming than 

 has Railroad Valley proper. The channel which traverses it is still open, though 

 seldom occupied, and no significant areas of local concentration are known. A small 

 stream apparently derived from the Hot Creek Valley underflow traverses the Twin 

 Springs Pass, but does not reach the main Raikoad Valley playa. 



There can be no doubt of the permanently inclosed character of the Railroad Valley, 

 and a series of old strand lines and wave bars witnesses its former occupation by a per- 

 sistent lake. (PL IV, fig. 2.) The highest of these strands is 155 feet by aneroid above 

 the main playa. 



The area now tributary to the main playa is perhaps 2,000 square miles. Includ- 

 ing Hot Creek Valley and its present tributaries and all the playas of the Railroad 

 Valley proper, the area is 4,555 square miles. Fish Spring Valley adds 415 square 

 miles, making a total of 4,970 square miles which is reasonably certain to have been 

 tributary to the valley during the Lahontan period. With the Kawich and Penoyer 

 Valleys, which were probably though not certainly once tributary, the total drainage 

 area would be 6,340 square miles. This is a maximum value. 



THE KAAVICH BASIN. 



The Kawich Valley has already been noted as lying south of the Reveille Valley 

 and separated therefrom only by an alluvial divide. This divide is now about 400 

 feet above the bottom of the valley, but has probably been considerably raised by 

 recently added alluvium. The writer is of the opinion that it is post-Lahontan and 

 that the Lahontan period drainage of the Kawich was north, through the middle por- 

 tion of the Reveille Valley, and thence northeast into the Railroad Valley. The pres- 

 ent floor of the Kawich Valley is a flat on which are a number of playas of the usual 

 character. The area of the basin is 370 square miles. 



THE PENOYER BASIN. 



The Penoyer Valley lies south of the Railroad Valley proper and is believed to be 

 separated therefrom only by an alluvial divide of recent origin. However, the maps 

 of the region are very inadequate and the writer's personal examinations have not 



