MONROE COUNTY. 
423 
Farther south and distant from the streams, through the towns of Penfield, Perrinton, Men- 
don, etc., the drift hills are of moderate elevation, giving a gentle undulating appearance to 
the country. In the south part of Perrinton the surface is very irregular, the hills rising 
from fifty to one hundred feet above the general level. These are composed of gravel and 
hardpan, and the general character of the soil is gravelly. Some of the hills are sandy, sup¬ 
porting a growth of shrub oaks and whortleberry ; the soil, however, is said to be good when 
reclaimed. West of the Genesee, few hills rise to a greater height than thirty or forty feet. 
All those in this part of the county rest upon the gypseous formation, and many of them 
are formed by the destruction of the upper portions of these strata. 
Most of the streams afford eligible mill seats, and it is to the water power furnished by the 
Genesee that Rochester owes much of her prosperity. The great accumulation of water 
power at that place, depends on the geological structure of ihe country. Had all the strata 
been of equal hardness, the grand and beautiful succession of falls and rapids would not have 
been produced, but in place of them a uniform, rapid current to the lake. 
The Mountain ridge, or “ limestone ridge,” so called, becomes well defined a few miles 
west of Rochester. Here its elevation is only fifteen or twenty feet, but it gradually rises 
towards the west, and at the western line of the county is forty or fifty feet above the level of 
the country on the north. This ridge or terrace does not pursue a direct line, but is tortuous 
and irregular in its course. 
In many places we find swamps or marshes with large accumulations of partially decom¬ 
posed vegetable matter, though none of it has yet become peat. The substance is usually 
termed “muck,” and is used in some places as manure. There are several of these swamps 
along the lake shore, where immense quantities of “ muck” are deposited. Others on the 
south side of the ridge road, exhibit finely comminuted vegetable matter, with trunks of trees, 
deposited, often to the depth of several feet. The trees growing in these swamps are com¬ 
monly black-ash, tamarack, and cedar. In the southern part of the county are several swamps 
of this character, where the vegetable matter covers a deposit of shell marl—both substances 
of great value as manures. 
Lake Shore. 
The lake shore of this county is for the most part low, the land gradually declining to 
the level of the water. The action of the waves, together with the ice, have raised beaches, 
which in many places protect the land from inundation during high winds. In the eastern 
part of the county, the banks are abrupt, consisting of gravel, sand and clay. These banks 
are gradually worn away by the waves, and the materials carried to points where the banks 
are low. By this wearing action the lake encroaches upon the land in some places, while 
the land is gaining upon the lake in others. In the course of a year, several feet of these 
banks are abraded by the waves. The wind from the northeast carries the abraded materials 
towards the mouth of the Genesee, and thus aids in filling up the channel, and extending the 
shoals and sand-bars in the vicinity. The shores being low on the west of the Genesee, a 
