The Medina formation consists chiefly of red shale. In the type district, about Medina, New York, the thickness is about 800 feet, and there are beds of sandstone in the upper hundred feet. Most of the sandstones are argillaceous and soft, but there are a few lenses comparatively free from clay. These are usually white or gray, and afford a strong, durable stone, extensively quarried for structural purposes.
From some quarries flags and blocks of large dimensions can be obtained, but others yield only small and irregular blocks, because the rock is traversed by cross-bedding. The oblique structure is of a peculiarly intricate type, often exhibiting dips toward all points of the compass in the same quarry, and associated with it are m any unconformities. There are places in the floor of the Whitmore quarry at Lockport where the strike of a dipping layer can . . .