658 REVIEWS 
peneplained surface in a broad dome, higher in the south than in the 
north, set to work again the forces of degradation. In the south greater 
elevation, highly tilted strata, and soft beds alternating with hard, of 
the Coal Measures, gave rise to great contrasts of relief. In the north, 
with less height, gently inclined strata and resistant dolomites and 
limestones very different relief effects were produced. 
The mountains of the Ouachita district appear to have tolerable 
even tops. In the novaculate region, in the extreme south, where the 
rocks are very hard, the mountains have only half the height of those 
a little farther north, but made up of softer beds, or soft layers alter- 
nating with harder ones. ‘The great Arkansas River has cut its broad 
valley through soft shales of the Coal Measures. Everything goes to 
show that the present aspect of the whole elevated region is the result 
of one grand recent bowing up. 
The correlations of the Coal Measures made by Dr. Drake are of 
great interest. In the June issue of this journal reasons were given for 
believing that nearly the whole of the enormous thickness of the Coal 
Measures of Arkansas was the equivalent of only the Lower Coal Meas- 
ures of Missouri and Kansas—the Des Moines series. Dr. Drake’s 
notes and map appear to afford conclusive proofs of this view. His 
great basal sandstone, ‘‘ Lower Coal Measures,” and the productive 
group (Cavaniol) taken together would appear to represent approxi- 
mately the Des Moines series. I say approximately, for it is not yet 
quite certain just what is the upper limiting horizon of the “ Cavaniol.” 
On his map, where the western boundary of the latter leaves the ter- 
ritory northward, it meets the lower member of the Bethany lime- 
stone—the basal stratum of the Missourian series, and Upper Coal 
Measures of the western interior coal basin. The presence of marked 
escarpments at various places beyond this western boundary line are 
also taken as indications of the southern extension of the Kansas 
Missourian. 
In like manner the Poteau group seems to be the equivalent of 
that part of the Missourian series of Kansas, below the Wabaunsee 
shales. Possibly its upper limiting horizon is even lower. 
We are certainly deeply indebted to Dr. Branner and his associates 
for a set of contributions of much more than passing general interest 
and of inestimable local value. 
C. R. KEYEs. 
