36 BULLETIN 54, U. S. DEPARTMENT OF AGRICULTURE. 
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 Mountains 
(White 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 Valley 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 drainage of their immediate surroundings 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 Valley 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 buried 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 Railroad 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. (PI.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 KAWICH 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 
