A series of papers of which this is the first presents the results and some conclusions regarding the generation of oil in rocks by shearing pressures. In this first paper attention is confined to the method of determining the soluble organic content of oil shales. Many problems were encountered in this phase of the work, both in the preparation of shales for extraction, actual extraction, and drying the extracts to eliminate the solvents, and in determining the effects of catalysts on extraction. Interesting discoveries include the fact that oxidation renders some of the insoluble organic matter soluble, and that shales which have been subjected to high shearing pressures give an extract with more volatile hydrocarbons than shales not sheared. A few conclusions are drawn regarding the origin of oil shales and the nature of their organic matter. These are opposed to the theory that oil shales are shales containing inspissated petroleum.