March 16, 1894. 
Sere N@r. 
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column. 
THE NEW GEOLOGICAL MAP OF PENN- 
SYLVANIA. 
BY J. B. WOODWORTH, HARVARD UNIVERSITY. 
THE chef @euvre of a geological survey is the map. It is 
a graphic story of the results achieved by the corps 
engaged inits construction, and shows by a glance wherein 
progress has been made in defining the limits of the 
natural resources of a state, in interpreting the age of its 
rocks, and in establishing the relations of these rocks one 
to another. It is a bird’s-eye view of the geological 
history of the area, and is an indispensable adjunct of 
the accompanying report. 
~The Second Geological Survey of Pennsylvania, under 
the direction of the venerable geologist, Prof. J. P. Lesley, 
has brought its results together in the form of a final 
report of which the first volumes and the map have 
appeared. The map, dated 1893, is in four sheets on the 
scale of six miles to the inch, and was made by A. D. W. 
Smith, assistant geologist, under the direction of Professor 
Lesley. It is drawn on a polyconic projection, and the 
data were the county maps published between 1874 and 
1892, together with other special maps of particular areas. 
The original map, so it is stated in marginal notes, was 
drawn on a scale of two miles to an inch and reduced by 
photography by Julius Bien & Co. to six miles to an inch. 
The legend contains twenty-two blocks of color, two of 
which have overprints to indicate trap and a limestone 
bed, respectively. The formation column is as follows: 
Posv-TERTIARY. 
Alluvium. 
Terminal moraine. 
CRETACEOUS. 
Potter's and Fire Clay and Sands. 
Triassic (Mesozoic). 
Trap, Red Shales and Sandstones. 
CARBONIFEROUS. 
XVII. Greene County Measures. 
5 XVI. Washington County Group. 
XV. Monongahela River Coal Measures. 
XIV. Pittsburgh Measures. 
XIII. Allegheny River Coal Measures. 
XII. Pottsville Conglomerate. 
XI. Mauch Chunk Red Shale. 
X. Pocono Sandstone. 
SCI NC: 
DEVONIAN. 
IX. Catskill. 
Chemung. 
Portage. 
} Genessee. 
Hamilton. 
Marcellus. 
_Corniferous. 
§ Candagalli Grit. 
| Oriskany Sandstone. 
WAU. < 
VII. 
VI. Lower Helderburg Limestone. 
SILURIAN. 
( Salina. 
4 Niagara. 
| Clinton. 
( Medina. 
>) Oneida. 
§ Hudson River. 
| Utica. 
\ Trenton Limestone. 
II 
Chazy Limestone. 
| Calciferous Sandstone. 
V. 
IV 
IMU. 
CaMBRIAN (including lower Calciferous). 
I. Quartzite. 
Slate. 
Phyllite. 
Serpentine. 
Gneiss. 
LAURENTIAN. 
Gneiss. 
The coloration is very similar to that employed in the 
*“ Geological Hand Atlas, Report of Progress X.,”’ which 
appeared in 1885, and, as in the case of that set of maps, 
the topographic base is omitted. While this omission 
leaves the colors without the variable shading of contour- 
lines, which is an obvious advantage where many shades 
of color have to be used, it detracts from the value of the 
map since the student cannot infer from the breadth of 
outcrop alone the relative thickness of a given forma- 
tion. Where the outcrop is contoured, the inclination of 
the surface affords the trained map-reader more satis- 
faction. 
The mother geological map of this state was published 
in 1858 by H. D. Rogers, from surveys made between 
1836 and 1857. The eccentricity of the nomenclature 
applied to the rocks makes this map well-nigh unintelli- 
gible to geologists of the present day. From this first 
general map to the hand-atlas of 1885 was a great step, 
embodying the results of the first ten years of the second 
survey. It is interesting to note that in the present final 
map many minor changes in the limitation of formations 
have been introduced. 
It is always fair to test a map by matching its boun- 
daries with’ those of adjacent areas, surveyed under 
different auspices. The geological map of New York on 
the north is by no means a contemporary of the present 
high-grade map of Pennsylvania, and be it said, to the 
chagrin, not of the geologists and palzontologists of the 
Empire State, but of the legislators and the people, the 
state has no map comparable to that of the coal common- 
wealth. New Jersey has a geological map the matching 
of which with the state across the Delaware is attested by 
the map under discussion, on which the Paleozoic and 
Archean rocks of northern New Jersey adjacent to Penn- 
sylvania areshown in continuous bands. Of Delaware little 
can be said, but Maryland on the south has, through the 
enterprise of Professors G. H. Williamsand W. B. Clark, a 
