THE CARBONIFEROUS SYSTEM. 127 
at Coshocton is 248 feet; at Newcomerstown, 293; at Port Washington, 
260; at Lock 17, 295, and at Urichsville, 275 feet above Lake Erie. East 
of this point it dips rapidly, and at Steubenville is below the level of the 
Ohio. The profile section of the Central Ohio Railroad shows a series of 
similar undulations which are in part identical with those already named. 
For example, from Bellaire to a point within two miles of Campbell’s 
Station the dip is uniformly south-east, though varying somewhat in its 
rapidity at different places. At the point last mentioned the dip changes 
to the west, but recovers its normal direction before reaching Camp- 
bell’s. From Campbell’s to the quarry east of Cambridge the dip con- 
tinues south-east. It there changes locally to the west, but recovers itself 
before reaching the tunnel. The dip is again reversed at a point between 
the tunnel and Castle’s. From this latter point it is variable to within 
a mile of Concord, where the south-easterly dip is very rapid, and con- 
tinues so—diminishing from 100 to 50 feet per mile—to Norwich. It is 
there reversed to 35 feet per mile west for four miles, thence it undulates 
ereatly, though the westerly dip prevails until within one mile of Coal- 
dale, where it again becomes south-easterly, and so continues to Newark. 
(Stevenson. ) 
A knowledge of the undulations which traverse our Coal Measures is 
of great practical importance, as they render utterly abortive any attempt 
to ascertain the position of coal seams by any system of triangulation or 
calculation based on a supposed uniformity of the dip. Such methods 
are worse than worthless, since they are liable to mislead. It is scarcely 
necessary to say that the only way in which the dip of the rocks, in any 
larger or smaller division of the State, can be determined, is by careful 
local observation ; and the only reliable method—aside from boring—of 
ascertaining the position of beds of coal which lie below the surface, is 
to acquire a knowledge of the succession of the strata, and judge of what 
is concealed by its known relations to what is exposed. 
The arches and troughs which have been described above affect other 
portions of our geological series beside the Coal Measures, and their con- 
‘nection with the general structure of the rocks which underlie the State 
is shown in the discussion of the causes of our topography, Vol. I., Part 
I., p. 39. 
IRREGULARITIES OF THE BOTTOM OF THE COAL BASIN. 
The folds described in the last section are plainly the result of dis- 
turbances which have affected the Coal Measures after the deposition of 
the entire series. They are proximately parallel with the Alleghanies, 
and are undoubtedly the gentler waves produced by the upheaval of this 
