564? Geological Society : Anniversm-y Address, 1842. 



our science is sure to profit from such a revision as our associate 

 will be enabled to present to us. He has indeed already given us 

 an earnest of his future communications, first in a letter to Dr. Fit- 

 ton, on the older deposits in the state of Pennsylvania, and cites 

 evidences in one tract confirmatory of the theory of terrestiial and 

 higoon origin of coal-beds, which was pointed out by Mr. Logan, 

 who, liaving led the way in this inquiry, is now extending it 

 in America. Notwithstanding the real value justly attached to 

 these views, which have been supported by the labours of Mr. De la 

 Beche, and which received an ample illustration in the last discourse 

 of Dr. Buckland, I must caution geologists against applying this 

 theory generally to all coal-fields because it has been found true in 

 some, for it is manifest, that in those tracts (and they are numerous 

 and large) where marine shells, ironstone and shale, filled with large 

 fishes, alternate with beds full of plants, confusedly piled together, 

 it will be impossible to account for the origin of coal by subsidence 

 or overflow of masses of vegetation in situ. 



In a recent communication on the Falls of Niagara, Mr. Lyell has 

 taken the opportunity of explaining the sections of the American 

 geologists who have described them, from Mr. Amos Eaton, who 

 first showed the order of the strata, though his comparisons with 

 British types were erroneous, to those of Conrad and James Hall, 

 who have successfully placed these groups in parallel with our 

 own Silurian strata. In showing the varied alternations of the hard 

 and soft rocks which form the Silurian system of that region, and 

 the exact inclination of the strata, Mr. Lyell exhibits chronometers 

 of the probable retrocession of the falls, indicating where the river 

 has worked back more rapidly when it had to recede through soft 

 shale and sand, and how the solid barriers of limestone have pre- 

 sented greater obstacles. These data are indeed only more correct 

 and more detailed illustrations of the general phaenomena advo- 

 cated by Bakewell, De la Beche, and the American geologists, that 

 the recession is chiefly due to the water undermining soft shale and 

 sand from beneath ridges of harder rock which are successively 

 plunged into the abyss. It is well however to observe, that, from an 

 inspection of the country, Mr. Lyell has modified his former view, 

 that the letting off" or bursting of the Lake Erie might be the ultimate 

 result of the retrocession of the Falls, for he now seems to incline 

 to the behef, that owing to the nature of the strata through which 

 they will have to work back, the final result will be the formation 

 of long and dangerous rapids ; while he justly points out how the 

 formation of canals and the demand of water for the use of the lower 

 country, which is passing from a state of forest to one of cultivation, 

 will cause a gradual diminution of the upper lakes, and thus prevent 

 a future catastrophe. But the chief point of interest in this memoir 

 seems to me to be the inference deduced from the occurrence of 

 beds of ancient fluviato-lacustrine shells near the top of the cliff's 

 bounding the defile of the Niagara, and necessarily high above its 

 present bed, that the river has worn down its channel through a tract, 

 in which the former water-courses (probably a succession of lakes 



