1888. ] 43 (Uhler. 
Here we see three oblong masses of sandstone rock, each more than 
thirty feet in length, separated by a few feet of water, the more super- 
ficial parts of which are a dense quartzite, rising like cliffs ten or twelve 
feet above high tide, and dipping from twenty to thirty degrees eastwardly. 
This is not the common dip of the undisturbed members of this series, and 
probably points to the exercise of tremendous energy in displacing a body 
of rock more than twenty-five feet thick, which at the bottom of the 
water, even now, covers more than a square acre in extent. 
The two masses lying farthest to the north and east are more generally 
impregnated with ferric oxide, and being of looser, sandstone texture, 
suffer more loss of mass from the disintegrating effects of the water and 
atmosphere. 
The most north-eastwardly cliff is exposed to the full force of the storms 
that beat in from Chesapeake bay, and the heavy ice cakes which are 
driven by the high winds of early spring plunge with terrific force against 
this side of the rock and dig out cavities near the water line. The most 
westwardly of these rocks has been cleft into two great pieces by a longi- 
tudinal division, and now lies slanting apart at an angle of about forty-five 
degrees. These pieces are composed in great part of dense siliceous 
layers, showing no grain, and weather on the upper surface into figures 
which resemble large fungi and foliated lichens. 
Ferric oxide plays an important part in nearly all the members of this 
_ mass, but especially in the more granular and less dense portions. The 
iron solution stains the siliceous grains, eats into their figure, solders the 
particles into layers, centres around particular spots, enclosing them with 
a compact shell, and sometimes develops nodular bodies, such as may be 
observed in many parts of the sandy region east of Baltimore. 
Proceeding from this island to the south-west shore of the Patapsco 
river we fail at first to find the white quartzite, but instead, there are long 
and wide stratified beds of brownish sandstone, which run back fifty feet 
or more in one exposure, and penetrate to an unknown distance into the 
sandy cliff on the northern shore of Stony creek. This is only a disguised 
form of our white sandstone which has been almost uniformly stained 
throughout by the ferric oxide. On the opposite shore directly at the 
mouth of this same creek there is a deposit of the overlying member of 
this sandstone series, which originally rested at a higher level than the 
sandstone beds on the opposite shore. By reason of the eroding energies 
of tide, frost and ice, this upper bed of coarse ferruginous sandstone has 
been undermined and thrown upon the bottom of what is now the mouth 
of the creek. This bed which now lies in water six to ten feet deep, is 
about twelve feet thick, over seventy feet! in length, and perhaps sixteen 
feet in width. 
It is a wonderful piece of structure from the curious way in which it has 
been altered into long hollow pipes, twisted slabs, and serpentine figures, 
brilliantly charged with the most intense metallic green, blue, red and 
yellow tints. How far it extends back into the adjoining country has 
