The Vance well brings out several points of interest. It adds to the known extension of basement rocks of igneous origin to central Ohio. In this well such rocks were largely gneiss and are comparable with similar deposits in large fields on the north in Canada. From this and other wells in western Ohio it is apparent that the surface of these crystalline deposits represents an old erosion surface with much local and regional relief. Next the Cambrian rocks of sedimentary origin are worthy of note both for the number and the thickness of sandstone strata and for the high content of sandy material in the dolomite components. In the Vance test the St. Peter sand was not detected by analysis but the unconformity between the Black River and the Lower Magnesian groups was defi itely marked by the abrupt change from limestone to dolomite. The brine at this horizon was decidedly weak but was comparable with others throughout western Ohio. The evidence shows clearly that the green shales at the unconformities and those within the formations are simply normal deposits and have no relation to bentonite. The chief coloring pigment is celadonite, a glauconitic mineral, derived through chemical changes from muscovite, and present through a wide range of the geological column.