The Cliiioplains of the Rio Grandt. — Herruk. 2>77 
block of land to warrant an adequate installation. It is now 
only a matter of time when this difficulty will be overcome 
and the vast area, capable of raising all temperate fruits and 
products (except potatoes), will become a vast garden. 
The writer, together with his brother, \V. H. Hcrrick, 
were charged wih the exploration of a part of this area and 
found the subterranean water universal and subject to aston- 
ishingly little variation of level during the entire season . Grav- 
el beds are frequent and little expense is required to install a 
500,000 gallon plant. 
On either side of the flood plain, the irregular tongues of 
the inclined plains projecting from the mountains form low 
bluffs, interrupted by the deltas of lateral arroyos at frequent 
intervals. These plains illustrate processes of erosion which 
seem largely to have escaped the careful study they deserve. 
They have been d'jscribed as peneplains by some geologists who 
have neglected the distinctions made by professor Davis in 
describing these structures. The writer is inclined so far to 
agree with Tarr'^ as to consider the peneplain a questionable 
term as applied \o the western structures known to him. 
These river clinoplains seem hardly to come under the head 
of base-leveling though the final result would be a base-level. 
We have, first of all, the flood plain as a plane of reference 
(though this is not a constant and its variations have had an 
important effect in the development of the lateral plains) . The 
flood plain, of course, lies practically at right angles to the 
clinoplains and its inclination is so slight as to aff'ord a refer- 
ence level also. 
The materials of these plains are not necessarily uniform, 
they consist superficially of the detritus from tlie adjacent 
mountains . In the immediate vicinity of Socorro, for instance, 
they contain fragments of rhyolyte, trachyte, pitchstone, an- 
desvte, scoria, basalt, granite, dioryte. hornblendic schist. Car- 
boniferous limestone and quartzyte, flint, etc.. all derivable 
from the Socorro and Limitar ranges. 
Near the flood plain the action of the river in earlier higher 
stages is easily observed. Sand-bar formation, secondary ero- 
sion, and the like, are common. Near the mountains, on the 
other hand, the remnants of the Tertiary formations are found 
• Ambk. Geol., vol. xxi, 6. 
