304 STEEP ALLUVIAL TERRACES. Book II. 
On the evening of October 16th we reached the western 
foot of the mountain. We had reached the Mora on the 
3rd, and had thus travelled for thirteen days along, as it 
were, the edge of the plateau, which in the east borders the 
valley of the Rio Grande, having at the same time touched 
the e treme eastern settlements of New Mexico. 
We had however not yet reached the actual soil of the 
lower valley, but only one of those inclined plains of debris 
which descend, in all the wider parts of the valley of the 
Rio Grande, from the foot of the mountains, or the adjacent 
steppes, close to the river, and which here break off, with 
a steep edge, jagged by small hollows and fissures. The 
soil of these steep lateral terraces, consists of large alluvial 
strata of sand, clay, and detached masses of rock. This 
region is quite destitute of water, excepting what falls at 
rare intervals, and only during three months of the 
year ; it bears a vegetation, composed of some species of 
grass, mostly in isolated spots, shrub-like Artemisia? and 
Chenopodiaceas, Algarobbice, Larrea bushes, the long green 
but mostly leafless thorns of the Fouquiera, and other 
thorn-bushes with or without leaves, various Opuntice and 
HJchinocactce, as well as several species of Jucca both 
dwarf and tall. This region is incapable of cultivation, 
which is limited in the valley to the bottom lands along 
the river, as far as they can be watered. The lateral 
terraces occupy the greater part of the valley, so that 
the cultivation is restricted to a narrow strip, and even 
this is interrupted in the narrows of the valley. The 
bottom along the river is therefore the only part of the 
valley of the Rio Grande where trees are found. A 
kind of poplar, low and broad, is seen in groups and 
in small woods, and some willows grow on the edge of 
the river. The valley, otherwise, from one mountain- 
