Review of Recent Geological Literature. 59 
cates the addition of the Coal Measures of Pennsylvania, and then a 
natural group of the first order would be produced, nearly equal to the 
Paleozoic era. “Were we to adopt for this grand terrane the name Appa- 
lachian group, we should have a properly constituted name for an actual, 
existing geologic group, free from theory, and its use would probably 
assist in the progress of science.” (p 60.) He would discard certain 
lithological names still used in classifications, as age can never be de- 
termined by lithological characters. “It can be indicated only by that 
which changes with time under the influence of some definite law, 
and fossils alone have this value.” 
In addition to his disbelief in the value of lithological features in 
determining the age of rocks, Prof. Williams has but little faith in what 
is called “persistent parallelism of strata,” without the aid of fossils. He 
points out several erroneous correlations made by this “parallelism.” 
One of these was by Hall who, claiming he had traced the rocks step by 
step from New York to the Mississippi valley, stated that the Waverly 
sandstone of Ohio was the same as the Chemung and Portage groups of 
New York. (p. 63.) Other mistakes were made by the geologists of the 
Second Pennsylvania Survey, who, assuming an average direction and 
rate of dip, identified formations by their altitude. The outcrops were 
followed from ravine to ravine or from quarry to quarry, and though the 
same method was pursued by both Mr. White and Mr. Carll, when the 
correlations reached Chautauqua county it was found that Mr.White cor 
related the Panama conglomerate with the third oil sand of Venango 
county, while Carll placed it entirely below the Venango oil group. Prof 
Williams says: 
“The fact seems to be, as we review the records of the survey, that the 
data of lithologic character of rocks and of thickness of the deposits 
were so constantly variable that the ‘theory of persistent parallelism of 
strata’ was little more than a theory, the exceptions to which were as 
numerous as the illustrations. It was a cut-and-try system of match 
ing together innumerable sections made up of irregular combinations 
of shales, sandstones, conglomerates, and limestones of various color, 
thickness, and texture. Whenever the gaps were over a mile or two 
long the adjustment of the theoretical dip, a few feet more or less to the 
mile, would enable the parallelism to fit any particular stratum in a 
given section. The fact that those who showed evidence of having 
noted the fossils, although they may not have identified them, were 
invariably nearer right than those who neglected them, strengthens the 
belief that the fossils, even in this case, were the most valuable means of 
-correlation.” (pp 111-112.) 
Among the various problems discussed we find the differentiation of 
the Carboniferous system: the Coal Measures or Pennsylvanian series: 
the Lower Carboniferous of the Appalachians and of the Mississippi 
valley: the Chemung-Catskill problem: the Waverly problem: and the 
Permian problem. The use of the name “Carboniferous” is considered 
unfortunate, and Prof. Williams advocates its abandonment in favor of 
the “Pennine system,” inasmuch as it is in the Pennine chain of hills 
