It is pleasant to see that Sir Daniel Hall's book on the soil has now reached its third edition. It will have a permanent place in British agricultural literature as the first book on the subject in the modern period, its distinguishing feature, which marked it off from its predecessors, is its clear recognition of the complexity of the soil problem, emphasized in the opening words and maintained throughout: “In the scientific study of soils, chemical, physical, and biological considerations are involved.” Successive generations of earlier workers had regarded soil fertility as essentially chemical, physical, or bacteriological. This book was the first to show British readers that all these different views had a basis of truth, but that each by itself was too narrow. The study of the soil, in short, cuts across the conventional divisions of science and brings together such apparently diverse workers as the physicist and the protozoologist, the mathematician and the plant physiologist, and others who in an ordinary scientific laboratory would be supposed to have nothing in common.