tile stone

I. Ord. Lang.: A tile. II. Technically: 1. Geol . ( pl .): Certain beds originally considered by Murchison to be the base of the Old Red Sandstone, but afterward transferred by him to the highest part of the Upper Silurian. They have been retained in this position, and are considered to be the transition beds from the Upper Silurian to the Old Red Sandstone. Salter proposed to call them Ledbury shales. 2. Petrol.: A name by which certain slates which cleave along planes of bedding are known. They form roofing slates.