No. 200,j 
331 
give the detail of the operation of these causes at the outlets of all the 
istreams; they are the same in all. 
Boulders — Erratic BlocksJ^ 
Boulders of different rocks are abundantly distributed over some parts 
of the county. They are perhaps most abundant north of the moun- 
tain ridge, and over the gypseous rocks in the south part of the county. 
In many places the surface is literally covered with them for a conside- 
rable extent, and again for a mile or two few are seen. These boulders 
are of the primitive rocks, as granite and gneiss, and of sandstone from 
the lower formation. In some cases we meet with pebbles or boulders 
from rocks farther south. Granite and sandstone are the prevailing 
boulders, but rounded and angular fragments of rocks of every formation, 
in the district, are found on the surface, some of them immediately above 
the original rock, and others at no great distance from it. The predomi- 
nance of feldspar is observed in all the granite boulders; many of them 
being of that variety called Labrador feldspar. This feldspar is very 
indestructible, and masses of that rock form some of the largest bould- 
ers in the county. Some of the spherical masses are eight or ten feet 
in diameter. These masses are in many places so abundant as to be 
broken up and used for building materials, for which purposes they are 
very durable. 
Soil, 
The prevailing soil of Monroe county is a gravelly loam, but we of- 
ten find clayey loam, sand, &c. extending over considerable areas. Ap- 
proaching the Genesee river on either side, the soil is more sandy; this 
character prevails, also, along the Irondequoit. Sometimes the different 
soils blend into each other, and at other times are quite distinct, or 
their limits are defined by the small streams. Sometimes changes of this 
kind are remarkable, where on crossing a stream the character of the soil 
is entirely different. The sandy soils are not deficient in carbonate of 
lime, and the sand from several feet below the surface is apparently as 
fertile as the original soil. Some of these sands require the addition 
of alluminous matter to render them of proper consistence for retaining 
moisture. 
Where there are no disturbances in the surface from streams or other 
causes, the character of the soil depends much upon that of the rock 
* We cannot, with propriety, restrict the term boulder to a rock distant from its original for 
mation; lor in the southern part of the State, rounded masses of the red sandstone are bould- 
ers; while masses of the same form are found on the limestone a few rods south, and in the 
soil above the original rock, which by that definition are not boulders. 
