Chap. XIIT. FEATUBES OF THE COUNTRY. 411 
Dr. Connelly, who a few years since made the first carriage 
track through the wilderness. This road,, at the watering- 
place Agua Delgada, joins the more frequented one which 
connects El Paso with San Antonio in Texas. 
The bearing towards this place, which we reached on the 
29th, is north-easterly. We travelled mostly by nights, 
and rested by day, so that I could make no connected exa- 
mination of the country. I can only say, in general terms, 
that the road from the valley of the Rio Grande, passes 
over sand and gravelly hills, through deep watercourses 
and over steep cliffs in the alluvial region, till it reaches the 
first terraced side of the valley. Farther from the river 
it ascends to hills of conglomerate, sandstone and limestone, 
respecting the geological character of which I can say 
nothing. Passing through valleys shut in by these hills, 
and over elevated plains, round which rise table-moun- 
tains composed of strata of sandstone of different colours, 
and limestone of various quality, we came to the perpen- 
dicular cliff of a terrace of porphyry, the surface of which 
forms a sloping plateau. Eising over this, we arrived at 
the base of the Puerto del Paisano, a pass in the porphy- 
ritic chain, which forms the direct south-easterly continua- 
tion of Sierra del Diablo, in which the Limpia Passes 
exist, and which in a more general sense belongs to the 
southern continuation of the Eocky Mountains ; for these, 
in their farthest southerly extension, stand here on the east 
side of Eio Grande, till by the great curve of the river, 
they come to take their place on the western bank, towards 
Cohahuila. From the level of the plateau on the east side 
of this mountain chain the country descends in terraces 
towards the centre of Texas, the road passing now over the 
table-land itself; then through the valleys by which it is 
intersected, and the sides of which are generally formed by 
