894 THE AMERICAN NATURALIST. (NOL. XXXII. 
entire series of deposits had never existed, or had been subse- 
quently obliterated. And gradual and tranquil as the changes 
now seem to us, they may appear infinitely more so when a 
perfect sequence among the strata of the whole globe shall 
become known — when a complete succession shall be estab- 
lished from the oldest to the newest rock. From what we now 
know, compared with the knowledge existing a few years since, 
we can readily infer that some distant places, or even nearer 
localities, may furnish links now wanting in the chain.” Hall’s 
phenomenal vitality carried him through a period of geological 
research in which some of his expectations were verified. 
*The Fourth District, extending from Chautauqua and Niagara 
on the west to Wayne and Chemung on the east, was practi- 
cally fully deciphered by Hall in its intrinsic stratigraphy, 
though the exact and complete outline of its formations has 
only recently been mapped. This region, so uniformly con- 
structed, and referring so perspicuously to its origin in just 
such conditions as prevail along the margins of existing conti- 
nents, appealed strongly to Hall’s logical temperament. He 
writes of it : 
«The analogy to recent formations is thus more fully seen; 
for we have precisely the same materials, differing only in 
degree of induration. We have the unaltered monuments of 
a widespread ocean teeming with life, and we find recorded its 
changes through vast periods of time. We now learn what 
were the conditions of its bed at these successive periods, and 
also what different characters it presented at distant points., 
The varying forms of its inhabitants are as well marked and as 
perfectly preserved as the recent species amid the mud and 
sand and pebbly bottoms of our present seas. The geographical 
limits of certain genera and species are as well defined in that 
primeval ocean as in the present ; and, as now, upon the same 
bottom, we find in some places great accumulations of organic 
forms, while in others they are rare or wanting. Like our 
present ocean also, we know that this ancient one was agitated 
by winds and moved by tides; the drifted shells and commi- 
nuted corals tell us plainly of waves and currents, while m 
other places the fine sediment and equally distributed organic 
