Mar., 1917] Columbus, Ohio, Quadrangle 147 



but mail}' miles of road are directed by streams or valleys. The 

 Scioto River is followed by one road all the way from Columbus 

 to the northern limits of the area and frequently by two for 

 short distances. Similar response is found along the Olentangy 

 River. Alum and Big Walnut valleys have proved sufficiently 

 influential to have at least one road follow each most of the 

 distance across the northern half of the area, but the road is 

 upon the till plain a portion of the way. The valleys are crooked 

 and streams more so, and the latter crowd closely under one 

 bluff then under the other necessitating many bridges if the 

 valley floor be followed. 



Wagon Bridges. — Over most of the smaller streams wagon 

 bridges have been built where the fords were formerly, or so 

 near, that obviously the ford crossing and its road connections 

 determined the bridge site; but this is not the case with many 

 of the larger bridges. Often narrow places, or sites with rock 

 banks on one side or both, or specially good drift or gravel 

 banks have been sought out for bridges, just the conditions 

 that were avoided when the fords were located. This has 

 necessitated the laying out of new roads and the construction 

 of crooked, indirect roads across the valleys in many places. 

 The bridge over Big Darby, midway between Georgesville and 

 Harrisburg, and the upper bridge at the latter place are good 

 illustrations of this principle. The bridge is located at a desir- 

 able place with reference to the stream, but where considerable 

 circuitous driving is necessary to use the bridge. So common 

 is this kind of response that a bridge, so placed as to make the 

 road straight across the stream, and continuous with roads on 

 opposite sides, is a rather rare feature in the area. 



In many places the suitable crossing, whether ford or bridge, 

 and particularly if a bridge, is approached by several roads. 

 A convergence of three, four and even five roads from one side 

 of the bridge and a corresponding divergence on the other side is 

 a frequent occurrence. 



Quarries. — Many opportunities are afforded by the physio- 

 graphy for access to the rock. Valleys are youthful and deep 

 enough to have been cut wtII into the rock. The steep-sided 

 valleys of the Scioto and several of its tributaries, and of the 

 Darby creeks are, in more than a score of places, the sites of 

 limestone quarries. Several old quarries are found south of 



