Drainage Systems of New Mexico. — Tarr. 269 
themselves. Such streams as the Chama and Puerco always 
have as much sediment in their grasp as can be carried. 
This overburdening of the river has brought about a new con- 
dition of things with which the steam is now complicated. The 
river unable to carry off all the sediment furnished to it, is lay- 
ing it aside in sand bars and flood plains until such time as the 
equilibrium shall be restored. This clogging increases to the 
south ; and, at Las Cruces, in southern New Mexico just north 
of the reef of rock at El Paso with which the Rio Grande is 
contending, the river winds in and out among bars of quick- 
sand and broad flood plains which are being added to each 
year. In this valley, the Mesilla valley, the river flows with 
an uncertain course and frequently changes its channel. 
The Rio Pecos is at present in about the same condition as 
the Rio Grande. It is building up its channel with the silt 
with which it is over burdened. This river is also in its youth, 
and, I believe, a rejuvenated youth. In its upper portion it 
flows in a canon-like valley of recent date very likely due to 
rejuvenation resulting from the plateau uplift. The condition 
of youth is well proved by the fact that great areas on the bor- 
der of the Staked Plains are entirely destitute of drainage. 
Arroyas are everywhere forming and many roads on hillsides 
have been abandoned because during a rain they have been 
transformed to arroyas. Much of the drainage is underground, 
and these subteranean creeks appear in or near the Pecos as 
great springs flowing many cubic feet of water per second, as at 
Roswell. 
Between the Pecos and Rio Grande there is a great area of 
country having no surface drainage seaward. I refer to the 
area lying between the Organ and San Andreas range on the 
west, the White Mts. and small outliers on the north, the Sac- 
ramento and Guadolupe Mts. on the east and the Hueco and 
El Paso mountains on the south. Between these mountains 
is a great basin which for the want of a better name I shall call 
the Gypsum Plains. The length of thi& basin is 125 miles or 
more and the width varies from 10 to 30 miles. From Sierra 
Blanca which attains an elevation of 11892 feet and is snow- 
capped the greater part of the year, and from other portions of 
the White Mountain range there are several brooks of good 
size flowing into the enclosed basin. The principal ones are 
Tula Rosa creek, Bonito creek and Three Rivers. Each of 
