Crawford.] 54 g [May ,5', 
materials interstratified Avitli submarine volcanic extrusions and 
also with subaerial volcanic ejectamenta. This ridge has been 
elevated to far above its present altitude (from 3,500 to 4,800 
feet) by forces from beneath the strata assisted by lateral pressure 
from the S. S. W., i. e. from the Pacific Ocean, which have 
caused foldings and plications toward the N. X. E. It has deep 
ravines eroded in its southwestern side, and the rugosities of its 
general surface show long continued, severe, and active erosion 
which has exposed at many places its dual formation and struct- 
ure. Two features that but seldom occur at such high altitudes 
in ridges of principally volcanic ejectamenta are here to be ob- 
served : (1) At an altitude of over 4,000 feet above sea level 
there is a large tilted stratum of arenaceous and plastic clays of 
irregular shape, more than three miles in length and with a thick- 
ness of from 10 to over 100 feet. This stratum extends from 
near the top of the ridge down its southern side for from 600 to 
3,000 feet at an angle of about 9° 28', and is covered by hard 
lavas and by peperino to depths varying from 10 to 300 feet. 
At three places it is exposed to view, on the sides of ravines in 
exposures about 1,500 feet long and of varying thickness. 
(2) Springs of cool water flow on this stratum to the surface of 
the Cerro and form a small creek, about 18 feet wide, and from 
2 to 2^ inches deep, which runs over an exposed part of the stra- 
tum for about 1,500 feet to its termination, and then the water 
disappears into the porous ejectamenta. This stream has above 
it only a small catchment or hydrographic area, not sufticient to 
re])lace the water it loses by evaporation in its course, and it is 
evident that this large flow of water has percolated through the 
loosely compacted strata superimposed on the clay, or circulated 
through subterranean fissures for over four miles from numerous 
mud springs found active on the northeast side near the apex of 
the cone Uval. Outside of or beyond the ravine in which the 
creek flows, wherever the surface of ejectamenta has been 
denuded down to ^Wthin 50 feet of the clay, the location of the 
clay and water in this side of the ridge is easily determined by 
the groves of large tall evergreen trees, such as nioperos, cedros 
ojoches, mahogany, etc., and also by the areas on which the coffee 
tree (Cafe arabica) flourishes. 
