656 
only being found common to the two, because he shows that both 
these deposits correspond exactly in the analogy which they bear 
to the fauna of the present day. Having also detected freshwater 
and land remains in the intervening tract, Mr. Lyell further offers 
us a satisfactory explanation of how the Miocene Faluns of the Loire 
and our Suffolk crag should be contemporaneous deposits and yet so 
different in contents, the seas in which they were respectively accu- 
mulated having been separated by dry land; that in which the crag 
was deposited opening to the north, and those in which the Faluns 
were accumulated opening to the south. 
Mr. Lyell’s works being before us, I seize this opportunity of con- 
gratulating the Society that a geologist possessing his powers of 
classification should now be occupied in studying the structure of 
North America. In that wide field, in which for the last few years 
the native observers have been gathering together both a vast pro- 
fusion of valuable detailed sections, as well as many general com- 
parisons with our own divisions, it is impossible that a good Euro- 
pean geologist can fail to reap an abundant harvest; and whether 
it be in his own tertiary domain, of which he has so largely ex- 
tended our knowledge, or by grappling with the Paleozoic rocks, 
which in that vast continent are developed on so splendid a scale, 
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 terrestrial and 
lagoon origin of coal-beds, which was pointed out by Mr. Logan, 
who, having 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 77 széz. 
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- 
