LETTER OF TRANSMITTAL.
Sir:—I have the honor to present the report of my late assistant, Mr. E. V. d’Invilliers, on the four counties of Union, Snyder, Mifflin and Juniata, descriptive of their geological structure, formations, mines and quarries, with notes on their soils and vegetation.
This report was handed to me in May, 1889, and ordered for printing in September, 1890, having to wait its turn among the public documents of the state, in charge of the Superintendent of Public Printing.
Before writing the report Mr. d’Invilliers constructed the two maps which accompany and illustrate its text, one of Union and Snyder, the other of Mifflin and Juniata, on the regular scale of two miles to the inch, and with the regular coloration of the geological outcrops adopted at the beginning of the survey in 1874.
These maps were engraved and printed by Bien & Co. in 1888–9, and have been lying at Harrisburg awaiting the printing of the report. Their beauty will be acknowledged; and every care has been bestowed upon their construction to make them as accurate as possible. In the absence of exact geodetic map-work by the U. S. Coast Survey, the State of Pennsylvania having never made a geodetic survey of its own region inside its boundary lines, the usual difficulties were encountered in adjusting the county lines to each other, and still greater difficulties in adjusting the townships in each county. But the geographical inaccuracies nowhere amount to enough to interfere with a cor-
