FISHES OF TEXAS AND THE KIO GEANDE BASIN. 
63 
The Rio Grande del Forte, or the Rio Bravo of the early Spaniards, is in many 
ways a remarkable river. Having its sources in the San Jnan Mountains of Colorado, 
only a few miles from some of the sources of the Arkansas and the Colorado of the 
West, it flows east to San Luis Park, then south through that park and entirely across 
Few Mexico, which it divides into nearly equal parts. Upon leaving Few Mexico it 
turns to the southeast, which general direction it maintains until it reaches the Gulf 
of Mexico in latitude 26° north and longitude 97° west (approximate). The total 
length of this river is about 1,800 miles, and it forms the entire boundary between 
Texas and Mexico, a distance of more than 1,000 miles and considerably more than 
half of the entire length of the boundary between the United States and Mexico. The 
tributaries in the San Juan Mountains are all clear, cold streams, excellent for trout 
but in the San Luis Park and below the stream is more shallow, the water is warmer 
and less pure, and trout disappear. Still farther down, except at a few places where the 
stream has cut through low mountains or hills and is confined in a narrow canyon, the 
river widens greatly, becomes very shallow, and has a bed of shifting sand and mud. 
Much of the country drained by the Rio Grande has an adobe soil, which contains a 
large amount of alkalies, and the water of the river is not only more or less alkaline, 
bnt contains much solid matter in suspension or other mineral matter in solution. 
This of course renders the water objectionable to many species of fishes. The Rio 
Grande is, however, much purer above the mouth of the Pecos than it is below, owing 
to the fact that the Pecos flows through softer strata containing a larger percentage 
of salt and gypsum. 
From Bulletin 3 of the Texas Geological Survey the following facts are taken : 
The banks of the Pecos River are lined with incrustations of salt left by the evapora- 
tion of the river water, and present a very white appearance. The sides of canals 
along the river are similarly incrusted and salt appears in spots over the ground. 
The following table contains the analyses of two samples of Pecos River water, 
made by the chemist of the Texas Geological Survey. Fo. 1 was collected at Pecos 
City and received at the laboratory in January, 1889; it gave an alkaline reaction on 
boiling, and had an alkaline taste; suspended matter made up largely of red soil, 
which settled quickly on standing. Fo. 2 was collected in Reeves County and received 
by the chemist in December, 1889 ; gave an alkaline reaction and possessed an alkaline 
taste; suspended matter made up more of silt and lighter soil than in Fo. 1, and 
settled only after 24 hours’ standing : 
Analyses of Pecos Kiver water. 
Grains per gallon. 
No. 1. 
No. 2. 
Total solid matter 
308.48 
319. 39 
Soluble after evaporation 
172. 59 
204. 70 
Total mineral matter 
255. 48 
259. 19 
Total lirno, as C.O 
27.42 
37. 62 
Total sulphuric acid, as S0 3 
64.57 
76. 73 
Total chlorine 
39. 05 
65.03 
Total alkalies, as chlorides 
58. 70 
106. 50 
Total potash, as oxide 
* 
2.95 
Total Boda, as oxide 
* 
66.08 
Total suspended matter 
36. 32 
85. 76 
* Not separated. 
It is not stated just when these samples were collected, but presumably Fo. 1 was 
taken in January and Fo. 2 in December, when the river was lower. 
