Chapter III.
Stratigraphical Geology.
The Palaeozoic Formations.—By reference to almost any one of the published reports of the Geological Survey. it will be seen that the Palaeozoic rocks of Pennsylvania have been divided into 17 general groups, numbered from No. I, Potsdam sandstone at the bottom, to No. XVII, the Permo-Carboniferous rocks on top.
Of these 17 general divisions, which have been sub-divided in many of the reports, the rocks of the “Juniata District,” through Juniata, Mifflin, Union and Snyder counties, are all comprised between the middle of the Siluro-Cambrian limestone No. II at the base and the middle of the Catskill formation No. IX at the top; consequently the Potsdam sandstone and part of the Lower Silurian limestone are hidden from view everywhere in this district, and all the formations, Nos. X to XVII, including all the carboniferous rocks and part of the Catskill No. IX are absent from the surface of these four counties.
As a direct result of this condition of affairs no coal-bed of merchantable quality or thickness that is to-day mined at any point in the state can ever possibly be found in this district, for the rocks in which such coal-beds occur do not exist here, and it is more than doubtful whether any attempt to find coal in the Devonian slates No. VIII will ever prove successful or of the slightest economical importance. Certain it is that its search in those rocks and in the still lower Hudson River No. III slates, which, despite every warning to the contrary, goes on time and again in many parts of the state, will entail much disappointment and loss of money to those foolish enough to engage in it.
Without uselessly going into detailed mention of vertical sections and descriptions of the various rock groups, the following general summary has been compiled from previous reports, to show at a glance the relative average thick-
