CHAPTER I. 
AN ACCOUNT OF GEOLOGICAL SURVEYS IN THE SOUTH 
MOUNTAIN BELOW THE SUSQUEHANNA. 
HISTORICAL KEVIEW. 
The first topographical description of South Mountain appeared as 
early as 1755. 1 It was made by Lewis Evans, of Philadelphia, who 
describes the South Mountain with a fair degree of accuracy, as "not 
in ridges like the Endless Mountains, but in small, broken, steep, stony 
hills; nor does it run with so much regularity." He continues: "In 
some places it gradually degenerates to nothing, not to appear again 
for some miles, and in others it spreads several miles in breadth." 
In a publication 2 which appeared in Germany in 1787 several pages 
are devoted to a general description of South Mountain. Two of the 
type rocks (the sandstone and the porphyry) were noted and aptly 
described, as the following quotation shows : 
One finds here and there gray laminated sandstones with quartz veins; fragments 
of coarse ferruginous quartz. At one spot on the road [from Sharpsburg to Freder- 
ick town] I found hlocks of gray -reddish porphyry with little transparent quartz 
grains intermixed, and milk-white opaque feldspars. *■ * * The South Mountain 
in its entire extent contains rich crevices, gangues, and nests of ore, especially of 
iron and copper. * * * I have still to add, from the observations made upon 
this journey, that the eastern slope is gentler and more gradual than the western. 
The most important publications on the South Mountain have 
appeared under the auspices of the various surveys of Pennsylvania 
and Maryland. The First Geological Survey of Pennsylvania was 
organized in 1836 under the distinguished geologist, Henry D. Rogers. 
The difficulties encountered, however, were so great that it was not 
until 1858 that the two quarto volumes of the survey were issued. 
Professor Rogers deals somewhat cursorily with the South Mountain 
region. He says : 3 
In its geological constitution, this tract is without much variety, for it contains 
scarcely any rocks except those of the Primal series. It is doubtful if the true 
gneissic rocks anywhere reach the surface withm its borders, and only in one or two 
localities have even the lowest members of the Auroral limestones been met with 
covering the upper Primal slates. Even of intrusive igneous rocks, it embraces a 
singularly small amount, those met with being chiefly greenstones and trap rocks. 
'Analysis of a Map of the British Colonies in America, 1755. 
5 Schopf's Beytrage zur mineralogischen Kenntniss ties ostlichen Theils von Nordamerika und 
seine Gebiirge, chapter 30, pp. 96-101, Erlangen, 1787. A translation of this work has been made by 
Prof. John M. Clark, of the New York State Museum of Natural History, to whose kindness the 
writer its indebted for a copy of the unpublished manuscript of the pages relating to South Mountain. 
3 Geology of Pennsylvania, Vol. I, Part II, pp. 203-209, 1858. 
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