242 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
less perfectly, after the manner of the theoretical streams, C 1 , etc., 
while hanging valleys already described, are found on the smallest 
branches, corresponding to G 1 , G 2 . 
No satisfactory evidence of terraces was found along the Chattooga, 
and it is presumed that the widening of the gorge has been sufficient 
to obliterate all traces of the former upland valley floor, as the con¬ 
ditions are similar to those imagined in figure 9, where the former 
terraces are consumed by valley widening. 
The “elbow of capture/’ which we were led to expect under the 
conditions of capture outlined, is beautifully shown where the Chat- 
tooga-Tugaloo turns abruptly from its southwest course toward the 
Gulf, to a southeast course into the Atlantic. A State boundary has 
been determined by this drainage modification. The continuation 
of the former southwest course pursued by the upland stream before 
capture, is indicated by Deep Creek. No valley or channel remains 
to mark the former course of the upland stream across the present 
divide northeast of Deep Creek, since the inverted stream was hin¬ 
dered in its development by the rapid growth of Panther Creek. 
Certainly the agreement between the expectable results of river 
capture and the features found to exist in the Tallulah district is 
most striking, and we are justified in accepting the theory of cap¬ 
ture as well substantiated. The conditions for capture were highly 
favorable; indeed, it seems inevitable that capture must have occurred; 
and on the basis of capture all the observed facts are grouped system¬ 
atically together and receive a rational explanation. We conclude, 
therefore, that the Chattooga formerly flowed southwest by way of 
Deep Creek, Soque River, and the Chattahoochee into the Gulf of 
Mexico, but was captured by the Tugaloo at a point below the junc¬ 
tion of the Chattooga and the Tallulah, so that the waters of both 
these streams were diverted to the Atlantic drainage by way of the 
Savannah River. 
The ultimate cause of the capture seems to have been the advantage 
gained by the Savannah River, the length of whose course to the 
Atlantic Ocean in the earlier geological periods, as now, was much 
shorter than that of the Chattahoochee, so that it was enabled to 
deepen its headwaters to a lower level than that occupied by the 
Chattahoochee, and finally to undermine it. There is no evidence 
of any advantage of rock structure, or stream volume, in favor of the 
Savannah, and the advantage of shorter length is wholly competent 
