146 



The Ohio Journal of Science [Vol. XVII, No. 5, 



Railroad Bridges. — The valleys are often so narrow in this 

 area that the railroads cross on bridges supported on tall trestles. 

 The Baltimore and Ohio over Big Darby Creek at Harrisburg 

 has a bridge 90 feet high and about one-fourth mile long. 

 (Fig. 5.) The Pennsylvania crosses the Scioto River at Marble 

 Cliff west of Columbus on a high bridge and leads up a long 

 rock terrace slope at the east end of the bridge to gain sufficient 

 height for the crossing. (Fig. 2.) The Cleveland, Akron and 

 Columbus crosses Big Walnut near Sunbury on a bridge high 

 enough to be flush with the till plain, and the Baltimore and 

 Ohio crosses Black Lick at Black Lick station in precisely the 

 same manner. 



Fig. 5. Bridge of Baltimore and Ohio railroad over Darby Creek at Orient. 



The track dips but little to make this crossing. Such a high level 



bridge is possible because the valley is in the youthful stage, 



and advisable because the valley is so deep. 



Alluvial fan slopes are sometimes used by the electric rail- 

 roads in getting out of and into a valley. The Arlington- 

 Grandview car so ascends from the Scioto flood plain across a 

 fan and up a little ravine to reach the upland till plain. All 

 these harmonious adjustments of railroads are responses of the 

 cultural to the physical. 



Wagon Roads. — It is probable that as many examples of 

 wagon road adjustment could be found as of railroad responses. 

 Many roads were laid out in "bee-line" from Columbus to the 

 neighboring towns, in order to facilitate communication between 

 them. Parallels and meridians are occupied by a few roads; 



