1 82 Bulletin of Laboratories of Denison University [Voi. xi. 
the sand supports very scant vegetation and only about its mar- 
gins a dwarf growth of cedar. The western slope is sparsely 
wooded affording fuel, some of which finds its way to Albu- 
querque. 
The San Filipe Mesa, 
The extreme north-eastern part of the sheet is occupied by 
a portion of the San Filipe mesa which fills the V-shaped area 
between the Rio Grande and the Jemes river. Nestled at the 
south-western margin is the picturesque Indian village of Santa 
Ana, while the similar village of San Filipe has a corresponding 
position at the south-eastern foot and the thriving town of Ber- 
nalillo lies east of the river opposite the point of the V. This 
mesa is really a part of the Albuquerque mesa and is similarly 
composed. It is simply severed from its ancient connection by 
Jemez river which we may surmise is a geological atter-thought 
of recent origin, and capped by an independent lava sheet from 
cones lying to the north beyond the limits of our sheet. There 
is the appearance as of several superposed flows but so far as 
can be gathered these appearances are due, for the most part at 
least, to differences of level resulting from erosion prior to the 
flows, though there is evidence that there were waves of the 
lava which represent intermittent phases in the flow. The iso- 
lated vent which forms the Bernalillo volcano has been eviscer- 
ated by the subsequent erosion of the river and now exposes to 
view the neck and radiating dykes as well as the effects of meta- 
morphism on the soft strata as explained and illustrated in Vol. 
I of this series. 
The Sandia Mesa. 
The Sandia Mesa occupies the south-eastern part of the 
sheet and rises from the Rio Grande flood plain which bounds it 
on the west to the base ot the Sandia mountains. The inclina- 
tion to the west may average about 75 to 100 feet to the mile. 
The slope is for the most part gradual and only slightly modi- 
fied by arroyos of recent erosion. The mesa is treeless but sup- 
ports a moderate growth of nutritious grass. The abrupt 
escarpments presented to the river face increase to the south- 
