8 o Bulletin of Laboratories of Denison University [ Voi. xi. 
strata are easily undermined and as they are removed by perco- 
lating water the lava above breaks into irregular fragments un- 
der its own weight and ultimately these fragments are indiscrim- 
inately dropped into the space beneath. 
To the north-east, nearly directly east of the peak known 
as Strawberry there is an extensive series of sandstone and 
shales some of which are full of gypsum fragments ; these 
are often tilted, dipping toward the range, i. e. to the 
west. No fossils have been found and it is at present impossi- 
ble to tell whether they are of Cretaceous age as the gypsuni 
might suggest, or whether they are of the same age as the 
other loosely aggregated material of the region farther south. 
Near tlie base of the range there are a number of ancient 
basaltic dykes which bear intrinsic evidence of a greater age 
than those forming the surface flows. They are interbedded 
and we cannot say from the exposures seen whether they have 
been intercallated in the series before the disturbance or whether 
they too were at one time surface flows, and since that time 
have been imprisoned under later sediments. 
Plate XI, Fig. 3. Panoramic view of the Socorro Moun- 
tains from the east, from a series of photographs, as seen from 
the city of Socorro. The numbers are placed with reference 
to sources of the rocks examined and will be referred to in the 
section on petrography, i. Strawberry Peak; 2. Socorro Peak, 
between this and i, Nogal Canon; 3. Promontory Peak; 4. 
Sharp Peak, north of which a dyke cuts off the limestone seen 
at 22; 5. similar small peak near which gold discovery has been 
made ; 6. western granitic part of main range ; 7. The upper 
and western of two flows of quartz trachyte flowing over ande- 
site at 27 ; 8. western wall of the old crater about one mile 
west of 7 ; 9. hill forming southern wall of Blue Canon, the 
lower part of andesite, upper of trachyte and rhyolite; 10 to 
13. various trachyte, rhyolite and breccia flows ; 14. Pallisade 
Mountain ; 15 to 19. hills of stratified gravel and sand covered' 
with a thin flow of recent basalt ; 20. flow of trachytic rock 
over the limestone; 21. quartzite at base of limestone; 22. 
Carboniferous limestone, about 400 feet thick ; 24 to 26. ande- 
