When, in the summer of 1931, Richard Alexander Fullerton Penrose Jr., died in Philadelphia, he left his personally acquired fortune, amounting to approximately ten million dollars, to be divided equally between The Geological Society of America and the American Philosophical Society. As a memorial to its benefactor and as a picture of a period in the history of American geological science, this volume has been prepared by The Geological Society of America. Beginning with notebooks, diaries, and letters in the possession of the Society, and adding thereunto material slowly accumulated from his family, his friends, his associates, and acquaintances, the story of his life has been pieced together. For members of Penrose’s profession, the geologists, this account of his life should have particular interest, for it presents a picture of a period which is gone forever, a picture of conditions under which the early investigators in geology and the mineral industry labored and brought forth the principles and methods of later days, methods more scientific, perhaps, but, nevertheless, methods founded upon the efforts of those pioneers. If one is inclined to smile at the picture of the young man of the 1880’s sitting on a bluff above a Texas river, confronted with the problem of making a survey without knowing how to go about it, let him ask himself what he would have done, similarly unequipped and in hitherto unknown territory. Let the geologist of today, with his carefully prepared field equipment, ask himself just how well he would like to look forward to “living off the country”, as Penrose did in the early days in Arkansas. It speaks volumes for the stamina of any man to be able to confront uncomfortable conditions with the nonchalance which Penrose displayed. And how much more to his credit this is, when a man is endowed by birth, position, and economic security so that he need never have left the comforts of urban living in Philadelphia.