claim: Georges Gilles de la Tourette described things.
evidence: A dike or dyke , in geological usage , is a sheet of rock that formed in a fracture in a pre-existing rock body .. geological usage. Geology. fracture. Fracture ( geology ). Dikes can be either magmatic or sedimentary in origin .. magmatic. Intrusive rock. sedimentary. Sedimentary rock. Magmatic dikes form when magma intrudes into a crack then crystallizes as a sheet intrusion , either cutting across layers of rock or through an unlayered mass of rock .. magma. magma. sheet intrusion. sheet intrusion. Clastic dikes are formed when sediment fills a pre-existing crack .. sediment. sediment