JVeoUthic Mdii ill y'lcardijiKi. — Ci-airford. 161 
surface and strata in other countries, whose geology is l^etter 
known, in order to determine the epoch when these people lived, 
and possibh' to decide on the cause of their flight. 
For a few feet south from the water margin of the lake, the 
formation is a coarse sand}- beach, then an abrupt cliflf' 8 to 12 
feet high above the surface of the water, thence south and south- 
eastward for more than a mile, the surface ascends to aljout 180 
feet above the level of the water in the lake, then commences a 
series of volcanic montecules, cones, craters, and cerros, some- 
what degraded by erosion, extending 25 to thirty miles eastward 
to lake Nicaragua. 
The stratum bearing impressions of human feet is near lake 
Managua, about fourteen feet beneath the surface of the soil, and 
on a level with the high water mark. It is not much inclined l)ut 
nearly horizontal with the present surface of the earth as it 
ascends south and east from the lake. 
The mineralogical composition of the strata from at least 
twent}' feet below the stratum retaining footprints of man and 
other niiimnuih^ up to the surface of the soil is aljout the same. 
The larger proportion of more acid minerals are near the soil, the 
general composition of all are rhyolite, trachyte, lipardite, phono- 
lite, pumice, basalt, dolerite,audesite and l)lack. also light colored, 
scoriae, all in particles (large grains or small fragments) and 
l)odies, mixed I)}' water with volcanic ashes ( and ores of iron ) 
into a conglomerate whose contained grains and fragments are 
weakly cemented by the ashes and oxides into strata varying 
from six inches to four feet thick and consolidated t<^ a hardness 
when in place, of from 2 to 2^ ( excepting the upper stratum 
which has not yet hardened sufficientl}' to be separaljle. from 
top to bottom, into blocks), containing four or more cul)ic feet; 
exposed to a dry atmosphere these rocks soon harden to 3.25 to 
4. Each stratum is separated from the one aliove it and, also 
the one below it, by a fine grained, Ayo.sv sand, colored light brown 
l)y iron oxides and varying in thickness from 2^ to 4 inches. 
Stratigraphically, the deposits, from at least ten feet l)elow the 
stratum impressed by human feet. \\\) to the surface of the eartii, 
are: 
(a) Superficial, 4 to 10 feet thick uncompacted or partly hardened 
ejecta conglomerate {'^) containing numerous patches or small areas of 
(3) Ejecta coiiL'loiin'riite in di^^tiiictioii from fused volcanic contrlomerates and 
" i-hingle ■■ and from " cont^lonicrate ■■ us di'tini'd liy I^yell, J)anu, Lo Conte, I'rcstwich 
