Effect of Elevation. 83 
striking mark this as a line of instability during the whole of 
Paleozoic time and the physiographic evidence shows that the 
= instability has continued down almost to the present. Hence it 
eems at least probable that orogenic activity has been persistent 
, the other axes in pre-Cretaceous or Paleozoic time, and that 
he forces which produced the Cincinnati arch are the same as 
those which have deformed the Cretaceous peneplain. 
Considerable evidence has been collected bearing upon the 
relative age of the oscillations recorded in the deformed pene- 
plain, but since it is closely connected with topographic features 
to be described later its consideration is postponed to a subse- 
quent page. 
DEFORMED TERTIARY PENEPLAIN. 
The long period of quiescence, during which the Cretaceous 
peneplain was produced, was terminated by a general elevation of 
the larger part of the province. Like most of the oscillations that 
_ have occurred since, it was compound in character, combining 
epeirogenic and orogenic movements; the former affected the 
entire province, carried the coast line considerably beyond its 
previous location and stimulated the streams to increased ac- 
tivity ; but the energies culminated along certain axial lines and 
resulted in pronounced orogenic uplifts that warped and twisted 
the surface as it arose. 
The immediate effect of this elevation was to stimulate erosion, 
and the streams which for a long period had been carrying only 
the finest sediments began the rapid corrasion of their channels 
and quickly trenched the rising land. The process was carried 
on differently in different parts of the province; where the ele- 
* vation was slow, erosion was very moderate in its effects, but 
where elevation was rapid the streams were greatly stimulated 
and rapidly dissected the peneplain. 
The movements which inaugurated this cycle still continued 
to affect the province, not continuously along any one axis, but 
by intermittent and gradually decreasing elevations and depres- 
sions. These oscillations were terminated by a second period of 
quiescence, during which the surface was again reduced to a base- 
level peneplain. 
; The extent of the movements occurring between these two 
periods of baseleveling can be roughly measured by the vertical 
