216 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
from one to another. Even the relative order of the successive cap¬ 
tures was believed to be established, since “the migration of Coosa- 
Tennessee fauna from west to east shows conclusively that the changes 
in drainage must have followed a similar order/’ 
In 1905, the writer published a paper on “The distribution of 
freshwater faunas as an evidence of drainage modifications,” in 
which the biological evidence of river capture presented by Simp¬ 
son was reviewed in some detail. It was shown that many means 
for the dispersal of molluscan faunas exist in addition to that of river 
capture; that the forms discussed by Simpson are found in other 
streams besides those which had been involved in the supposed cap¬ 
tures; and that there was evidence tending to show that the reported 
capture of the Tennessee River, to which the biological evidence 
principally referred, had not taken place. From this it was con¬ 
cluded that the evidence brought forward by Simpson was not a 
valid proof of river capture, and that the captures referred to, includ¬ 
ing that in the Tallulah district, would have to be established, if at 
all, on some other lines of evidence. 
In the February number of the American geologist, 1901, there . 
appeared a paper by S. P. Jones, entitled “The geology of the Tallu¬ 
lah Gorge.” Mr. Jones discussed the geology of the region, recogniz¬ 
ing three main types of rock, only one of which, a quartz schist, 
occurred in the immediate vicinity of the gorge and falls. The possi¬ 
bility of capture already suggested by Hayes and Campbell, was con¬ 
sidered, but no conclusion reached. The probable former course for 
the original* southwest continuation of the Chattooga River, (suppos¬ 
ing the capture did occur), was suggested, although nothing like river 
gravels could be found along that course. As an alternative theory, 
it was suggested that the steepness of the gorge might be due to “dif¬ 
ferential movements that.... in some way caused particular activity 
in stream erosion at this locality.” The necessity of some explana¬ 
tion for the absence of a gorge along the Chattooga similar to that 
below the falls of the Tallulah was stated, but no such explanation 
was offered. Further reference to the details of this paper will be 
found in subsequent pages. 
In reviewing the paper by S. P. Jones on “The geology of the 
Tallulah Gorge,” Professor W. M. Davis, in Science for 1901, writes 
as follows: “The precise order of events in the development of the 
gorge does not appear to have been made out; indeed the author 
