598 
1. Niagara limestone, lower beds............- 30 feet. 
2. Niagara, or Rochester shale... 2.1... .....- 80° 
32 eProtean Med sian, 5120) 2 yehee leek teeter epee Ve tts 30 — 
4, Ontario group: red marl, with hard beds in 70 
Phe MS PEK) PAT tin | Se sv. ce stebn ey naiel eaeeehens cl 
—_—_—: quartzose grey sandstone, Re 
pwatly Dare ullee Ore. iia). tens, sien title iar er tet etiote 
6. —— ered marlin.) (OIG. a) ey ecee veky 100 — 
335 feet. 
Though only the lower beds of the Niagara limestone occur in the 
escarpment at Lewistown, yet, in consequence of the gentle rise of 
the strata to the north, the summit of these lower beds is at a higher 
level than that of Lake Erie. The whole of the Niagara platform is 
covered irregularly with hillocks of drift, beneath which the lime- 
stone is polished and furrowed. 
From the foot of the Queenstown escarpment to Lake Ontario, a 
distance of six or seven miles, is a low tract, consisting of sandstones 
belonging to the Ontario group, and dipping like the preceding beds 
slightly to the south. 
A section which accompanied the memoir to illustrate the pre- 
ceding details corresponds, the author says, in all essential particu- 
lars with one previously published by Mr. Hall; but the whole suc- 
cession of beds has been verified by Mr. Lyell in more than one 
line of section, from north to south. He is induced to believe, from. 
a comparison of English Caradoc and Llandeilo fossils with suites of 
organic remains examined in America, that a series of beds which 
underlie the Ontario group, and termed by American geologists the 
Mohawk group, may be older than the lower Silurian rocks, and 
wanting in England. 
II. On the Recession of the Falls.—The following measurements, 
Mr. Lyell says, are of great importance in speculating on the past or 
future recession of the Falls. ‘The distance from the point where the 
Niagara flows out of Lake Erie to the Falls is sixteen miles, thence 
to the limestone escarpment seven miles, and from this point to Lake 
Ontario about seven more. From Lake Erie to the commencement 
of the rapids, fifteen miles and a half, the river falls only 15 feet; 
but from the top of the rapids to the great cataract the descent is 
45 feet; and the height of the Falls is 164 feet, perpendicular. From 
the base of the Falls to Queenstown, seven miles, the difference of 
level in the river is about 100 feet; but from that place to Lake On- 
tario, seven miles further, it is only 3 or 4 feet. If the Falls were 
ever at Queenstown, they must, the author observes, have been about 
twice their present height, having lost a small portion of the dif- 
ference by the southern inclination of the strata, and rather more 
than 100 feet by the rise of the bed of the river. 
With respect to the opinion of the Queenstown escarpment being 
due to a fault, Mr. Lyell states, that the strata on the banks of the 
Niagara, both above and below Queenstown, presenting the same 
relative position as at Lockport or Rochester, the escarpment must 
