62 Ferrel on the Cause of the Inundation of the Nile. 
an almost universal generic identification, establishing fully the 
equivalency of the Chemung, Marshall, Ohio, Rockford, Burling- 
ton and Chouteau strata. The evidences that these localities are 
all of Carboniferous age are: 1st, The fact that, of the 185 spe- 
cies now known from the yellow sandstones of Burlington, no 
less than 40 ascend into the base of the Burlington limestone, 
while two rise to the upper portion of it, and one recurs in the 
Coal Measures. 2d. The fact that, of the known species of this 
horizon, at least 9 occur in the Coal Measures, or upper part of 
the Carboniferous limestone; while 3d, multitudes of species are 
clearly the local representatives of Huropean and American Car- 
boniferous types. 
Prof. Hall’s recent declaration in the Canadian Naturalist, that 
large areas of the rocks of New York hitherto regarded as Che- 
mung do really fall within the limits of the Hamilton group, 
will at once account for the Devonian aspect of some portions of 
the Chemung fauna, as heretofore understood; and thus tend to 
confirm a broad generalization, and complete the adjustment of 
American to European Paleozoic formations. 
Art. IX.—On the Cause of the Annual Inundation of the Nile; 
y WILLIAM FERREL. 
certain. 
Of the theories which have been advanced to account for the 
annual inundation of the Nile, the last, I believe, is that set forth 
by Sir R. L. Murchison in his annual address before the Royal 
es hushinal Society in 1859.’ Taking it for granted that lake 
Nyanza is the source of the Nile, this theory attributes its annual 
inundation to the abundant discharge of water from this lake 
uring the rainy season; but it seems to me that this theory 18 
not tenable. According to Captain Speke the rainy season only 
a little south of this lake, is from November to March, and con- 
sequently cannot vary much from this period at the lake; but 
* See this Jonrnal, Geographical Notices, vol. xxviii, p. 411. 
