Shale oil has been produced throughout the world for over 100 years by heating oil shale to a temperature such that the organic matter is converted to oil, gas, and coke. While considerable work has been done to establish the relationship among temperature, time, vapor removal, and quantity and quality of products, the essentially empherical manner in which the oil shale pyrolysis has been studied is indicated by over 100 patented retorts in this country alone.