552 Geological Society : Mr Lyell on the Recession 



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 

 be entirely due to denudation ; and he has no hesitation in attribu- 

 ting this escarpment, as well as the Helderberg, to the action of the 

 sea ; these great inland cliffs having far too great a range to have re- 

 sulted from a former extension and higher altitude of Lake Ontario. 



The next question, whether the ravine through which the Niagara 

 flows is to be regarded as a prolongation of the Queenstown escarp- 

 ment and referable to the same period, or has been cut through by 

 the river, is, the author states, of greater difficulty. From his own 

 observations, he concludes that the ravine has been formed by the 

 river ; but he assumes, that a shallow valley pre-existed along the 

 line of the present defile, resembling the present one between Lake 

 Erie and the Falls. His reasons for conceiving that the river has 

 been the excavating agent, are, 1st, the ravine being only from 400 

 to 600 yards wide at the top, and from 200 to 400 at the bottom, 

 between Queenstown and the Whirlpool ; 2ndly, the inclination of 

 the bed of the river, 14^ feet per mile, being everywhere cut down to 

 the regular strata ; 3rdly, the fact that the Falls are now slowly re- 

 ceding ; 4thly, that a freshwater formation, which the author ascribes 

 to the body of water which flowed along the original shallow valley, 

 exists on Goat Island and half a mile lower down the river, and 

 could not have been deposited after the Falls had receded farther 

 back than the Whirlpool. Mr. Lyell considers that the indentation 



