554 SOUTHERN TERMINATION OF ROCKY MOUNTAINS. Book III. 
III. — A mountain -chain, called the Sierra de los Nim- 
bres, has been laid down as the connecting link between 
the Eocky Mountains and the Sierra Madre ; but the travel- 
ler in vain seeks it at the designated spot. I have before 
spoken of this circumstance in relating my travels through 
that territory, and stated that the Rio de los Nimbres, which 
has its rise in the southern spurs of the Coppermine Moun- 
tains, flows in the rainy season over extensive plains as far 
as the Laguna de Santa Maria. There is, consequently, 
on the eastern side of this small river no space for any 
link of connexion between the Eocky Mountains and the 
Sierra Madre ; whilst, on the western side, if it existed, 
Leroux's Eoute must pass over it. I do not know this 
route from personal experience, but I have been assured 
by all those of my acquaintance who have travelled on it, 
that they passed over no mountain-chain, nor any consider- 
able height. 
IV. — Having thus shown that the Eocky Mountains, as 
a connected range, extend, on the western side of the Eio 
Grande, no further south than the narrow valleys below 
Yalverde, I will now trace the detached groups and chains 
of mountains, which form, on the eastern side of the 
river, the southern continuation, or at least the southern 
equivalent, of this system. The traveller journeying from 
San Antonio, in Texas, to El Paso, or the Presidio del 
Norte, must cross mountains which, west of the Pecos, 
mark a step of the ground over which the highest region 
of the plateau of western Texas is reached. The route 
across this range of mountains to El Paso leads over the 
Puerto de las Limpias, or " Wild Eose Pass ;" and that 
to the Presidio del Norte, over the Puerto del Paisano. 
I have before described these interesting defiles and their 
picturesque scenery, and I have observed that the moun- 
