388 The Mountain Axes near Cumberland Gap. [ July, 
ains, then at a succeeding time there was an upheaval that affected 
a deeper set of beds and formed far wider folds, on which the 
earlier uplifts were upborne as the lesser waves of the sea upon 
the greater ridges. At the same time the broader folds were 
much faulted, so that the whole mass became exceedingly compli- 
cated in its structure. The Appalachian system, in its ex- 
tremely varied yet comparatively simple conditions, presents us 
with a number of peculiar connections and separations of these 
two classes of folds. The Cincinnati axis, for instance, is a sam- 
ple of the broad fold of the simplest character. This fold seems 
to have been lifted with extreme slowness, and has a height of only 
a few hundred feet, being certainly not over fifteen hundred feet 
in height at any part measured from the bottom of the synclinal 
to the top of the ridge. But notwithstanding the slow formation 
and moderate elevation of this fold it has been somewhat affected 
by faulting in a direction transverse to its axis; these faults are, 
however, relatively very small. It seems to me that the East Ten- 
nessee region has had its form given by an effort to produce very 
broad and long anticlinals somewhat on the Cincinnati model, 
but of far greater height. One of these ridges, the Cumberland 
anticlinal, if it had retained its form, would have had a length ex- 
ceeding one hundred and fifty miles, a width of sixty miles, and a 
height exceeding twelve thousand feet. The parallel faults re- 
duced its height to less than half this height, and left an indistinct 
central anticlinal and a set of parallel fault mountains, one on the 
west, and four or more on its eastern side. According to the theory 
of De Beaumont these several mountain ridges, the central an- 
ticlinal and its several parallel monoclinal or fault-mountains, 
should have been of the same age, the product of a single cat- 
aclysm. The evidence, however, has led myself and my assist- 
ants of the Summer School of Geology and the Kentucky Survey, 
who have studied this country, to a very different conclusion. We 
have been forced to the conviction that the central anticlinal 
is of relatively ancient age, dating back primarily to a tıme 
soon after the expiration of the carboniferous time, while the 
other monoclinal mountains have been more or less gradually 
formed, some having been uplifted at a geologically very recent 
date. This succession has been determined by the only means we 
have of fixing the age of neighboring parallel faults in a région 
of this description, namely, by comparing the rate of the escarp- 
ments formed by the several fractures. The central esearpments 
as will be seen from the accompanying figure, there covering the 
