F. Enriques and G. de Santillana have begun in collaboration the composition of a general history of scientific thought. The first volume of this work, which has been recently published, is concerned with the science of antiquity,1 and to a large extent covers the same ground as the history of ancient philosophy, as the frontiers of philosophy and natural science, at any rate until the time of Aristotle, were not yet clearly differentiated. But the two historians are interested in bringing into prominence a great many problems and personalities that the history of philosophy generally leaves on one side, although they help to complete and vivify the picture of the mentality of the ancients. Mathematics, medicine, geography, astronomy, applied mechanics, and physics, in short all the particular scientific studies that were just beginning to detach themselves from the parent trunk of general philosophy are studied by the authors in their individual developments and through the personalities of their cultivators. The explanations are clear and simple and can be followed even by readers unversed in science; the information is at first hand and is supplemented by a careful discussion of sources. The scientific questions are not isolated from the historical setting of the civilization of antiquity, but are shown in relation to matters of philosophy, religion, art, and moral and political life. The bibliography, intended for the more purely scientific and technical departments of philosophy, forms a very useful and timely completion of the bibliography of philosophic thought in general.