602 



THE POPULAR SCIENCE MONTHLY 



stretch of straight track in Georgia, from a few miles southwest of 

 Waycross to a few miles beyond Valdosta, sixty miles in all, crosses the 

 head-waters of the Okefinokee. 



The geology of this flat pine-barren region is comparatively simple. 

 The surface is a few inches or a few feet of Columbia sand, and under 

 that is the clay, loam or coarse sand of the Altamaha Grit or Grand 

 Gulf formation to a depth of three or four hundred feet. None of 

 these formations are fossiliferous, but they are believed to be quite 

 recent, j^robably of Pliocene or later age. Under them is a limestone 

 believed to be Miocene', and below that presumably all the older coastal 

 plain formations in succession. There is every reason to believe that 

 the whole swamp is underlaid by the same formations, from the 

 Columbia down. 



Immediately east of the Okefinokee is one of the most interesting 

 topographic features of the region, which would scarcely be noticeable 

 but for the general flatness of the country. It is a broad low ridge, 

 exactly parallel with the coast and just about forty miles distant from 

 it. This ridge has been traced by the writer from a few miles west of 

 Jesup southward into the great bend of the St. Mary's Eiver, and about 

 thirty miles into Florida, where it is known as the " Trail Eidge," and 

 happens to coincide in part with the Atlantic and Gulf divide and with 

 the eastern boundary of Baker and Bradford counties, though still 

 maintaining its parallelism with the Atlantic coast. It is not an impor- 

 tant divide in Georgia, though no streams intersect it between the St. 



Abandoned Drainage Ditch near Camp Cornelia. 



