One of the peculiarities of the oil industry, in which it differs from many of the other industries using the minerals of the earth, is that its supplies of crude oil must be replenished continually by new discoveries. It is in the field of oil discovery that the petroleum geologist finds his chief work.The use of the microscope, with the consequent increase in detailed and accurate stratigraphic data has been proved one of the most important tools of petroleum geology. Not only does it give a better understanding of underground stratigraphy, but it also has stimulated an awareness of the importance of geologic history in the discovery process. The present trend is strongly in the direction of the application of this sort of data to the problems of stratigraphy and sedimentation.There is a growing trend of petroleum geologists into executive and managerial positions within the industry and into the oil business as independent operators. Probably as a result of this broadening viewpoint, there is developing a greater interest in the college curricula of geological colleges. In many ways, the petroleum geologist is becoming an "oil man," which, after all, is proof of his place in the industry.