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GEOLOGY OF THE FOURTH DISTRICT. 
CHAPTER XIII. 
Position and mode of transport of the great northern boulders. 
The general contour of the surface of the Fourth District has been already described, and 
the limits of the successive terraces and plateaux are not more perfectly defined than is the 
distribution of granite boulders, particularly in the northern part. That portion occupied by 
the Medina sandstone, and forming the first plateau above Lake Ontario, is often plentifully 
covered with boulders. These usually lie upon the surface, and always upon the previously 
described deposits of drift. They are not evenly distributed, but often appear in immense 
numbers, scattered over several acres ; while beyond this, for a greater distance, few are to 
be found. There appears to be no law regulating their distribution, though they are more 
abundant in the eastern than in the western part of the district. 
In passing along the Ridge road from Wayne county to the Niagara river, these boulders 
may often be seen in immense numbers on the low ground just north of the ridge, as if they 
had been brought there while the water was limited by this barrier, and spread over the bot¬ 
tom in shallow water near the shore. 
In higher situations, and just beneath the great limestone terrace, they again appear in 
abundance, as if this elevation prevented their farther advance to the south. Standing upon 
this high plateau and looking over the low ground on the north, the position of these boulder- 
fields can be distinctly traced. They are thickly scattered over spaces varying from a quarter 
of an acre to two or three acres, and sometimes even more ; and these spots are separated 
from half a mile to two or three miles, with only a few stray ones between. 
The broad plateau formed by the surface of the Niagara limestone and the Onondaga salt 
group, is sometimes thickly strewed by boulders of granite. The most abundant fields are 
in Wayne, and the eastern part of Monroe county ; and going westward from the Genesee, 
they are less so, becoming extremely rare in Erie and Niagara counties. They occur here in 
the same manner as before described. 
As we ascend the second limestone terrace, formed by the Helderberg range of limestones 
extending westward, boulders become perqeptibly less numerous ; they arc irregularly scat¬ 
tered, and at few points present the thickly covered fields which we observe a few miles far¬ 
ther north. Very few ascend the slope formed by the passage of the Hamilton group to the 
rocks above; and in all the previous cases, they seem to have been brought on at intervals in 
great numbers, and their limits bounded by the different elevations of the surface. 
