and Susquehanna valleys for the last two years rendered this impossible.
The two colored geological maps of the four counties.
In the construction of the four county maps accompanying this report every effort was made to use all reliable data which could be obtained during the progress of the survey: but as much valuable material regarding the courses and distances of the various county lines was submitted too late for any practical use, owing to the advanced stage of the map-construction and the conflicting testimony of some of the lines, it was deemed best to use this data only as far as it was possible to do so without doing violence to points already established by railroad surveys and township reductions.
All this material has great relative value however, and in order to preserve it as a record for future compilations and corrections, the correspondence is published below.
The general base for all the county maps was established by reducing to one common scale of one mile to one inch all the railroad maps kindly furnished by the Pennsylvania, Northern Central, Philadelphia and Erie, and the Philadeldelphia and Reading railroad companies, by which means the location of towns, villages and large streams were fixed with comparative accuracy.
Unfortunately the failure to obtain any good map of the main line of the Pennsylvania Railroad from Rockville, or Marysville, west, along the Juniata to Mt. Union, prevented the establishment of points along that river in Juniata and Mifflin counties with definite accuracy. And while an attempt was made to fix the location of Lewistown Junction by a reduction of right-of-way maps along the main line, with a common point determined by independent plottings of the Sunbury and Lewistown railroad, such violence was done to township maps of Juniata and Mifflin county as to make their use absolutely impossible.
With Rockville and Selinsgrove Junctions as fixed points therefore, the lines of the Sunbury division and main line were each swung slightly to meet at a common point, Lewistown; with the possible effect of slightly warping a por-
