100 
on the S. E. border were first deposited on this N. W. slope; 
and then that the upper edges were worn off, and the material 
carried further N. W. to be again deposited and form new 
strata upon the lower parts of those already deposited. 
Without any addition of material, there would, in this way, 
be a multiplication of strata all having the same dip. 
And such a process could go on, until the formation had 
widened out to its present extent. Such a mode of forma- 
tion, would not require that the whole series of strata should 
be more than a few hundred, or possibly a thousand feet in 
thickness. This ingenious notion is upset, by an observation 
first made by the author of an abundant occurrence in the 
coarser beds, as for example, under the trap at the Passaic 
Falls, of fragments of the Green Pond Mountain chain lying 
to the North West. 
President HircHcocx’s argument of original approximate 
horizontality, drawn from the “ bird-tracks,” appears cogent, 
and, in fact, unanswerable. Moreover, it is hard to see how 
the above hypothesis necessarily reduces the length of time or 
end of deposition, even if it be fully accepted. Between the 
Carboniferous and Cretaceous, an immense period is repre- 
sented in Europe, while RAMSAY makes there at least three 
complete breaks in succession, each of which he believes was 
greater in duration than the rock-making periods between, 
whilst here we need not suppose any breaks. The author 
argues from the general ferric condition of the Iron, that the 
beds are of fresh-water origin, as the Iron in marine sedi- 
ments is usually ferrous. Also this ferric condition shows 
that there might have been a great abundance of organic life, 
whose remains were chiefly destroyed by the powerful oxid- 
ating agencies at work. His theory previously presented to 
the Lyceum, of the relations of silica in isolated mineral 
forms, to life, led him at this point in his investigation, to 
examine the nature of the cement or paste, which concretes 
these rocks, and which has heretofore been assumed to be, 
in the granular beds, ferric oxide. Some have also supposed 
the presence of silicates and Carbonate of Lime and Magnesia, 
Dolomite, etc. Boiling Muriatic acid, however, removes all 
