That a thorough knowledge of optics is the best foundation for the proud edifice of ophthalmology there can be no doubt. The usual textbooks of physical optics always contain a good many things that do not directly concern the beginner in ophthalmology, and on the other hand they frequently omit points about which he desires to obtain full information. A book, therefore, in which there is presented that part of the optics which pertains directly to ophthalmology must be welcome to the oculist. Such is the character of the book that has been written by Dr. Souter who is to be congratulated on his work. Concerning his intentions the author says in the preface: "Simplicity has been sought so far as this is not incompatible with thoroughness; for whosoever would become versed in ophthalmology as a science must, in the beginning, make the mental effort necessary to acquire a clear understanding of the refraction of light through a compound optical system, such as the eye." The author has succeeded phenomenally in setting forth clearly some of the highest problems of physiologic optics, and what is more to the point, any earnest student will be able to follow him because simple algebra and elementary geometry alone are made use of. After a few introductory remarks concerning the wave theory of light, the author deals with refraction as occurring at plane surfaces and through prisms giving a simple but forceful demonstration of the minimum of deviation. We miss in this chapter a definition of the central of Dennett, the prism-diopter of Prentice, and the metro-angle of Nagel which would perhaps be more satisfactory to the student than reference to the original papers. The second and third chapters deal with refraction at spherical surfaces and through lenses thus leading up to the most important point-the eye as an optical system. This latter subject is not treated in the elaborate manner of Helmholtz, but none the less in a thorough, although rather slower, method which, however, being less abstract will be of greater benefit to the average student. His calculation of the cardinal points is from the constants found by Helmholtz. The effect of lenses on these cardinal points in emmetropia and ametropia, as well as their influence upon the size of the retinal images, is fully explained in chapters 4, 5 and 6.... The subject of cylindrical lenses, then torsional properties, and the resultants of their various combinations embraces about 40 pages. The author shows very clearly the sphero-cylindric equivalent of two cylinders placed with their principal axes oblique to each other. As is well known, this has been done before by Bonders, Jackson, Hay, Prentice, Wilson and myself, but the author's apology for adding another solution to those already published is that "in all these solutions the process of eliminating the special point at which the ray meets the lens is unnecessarily tedious.'' He objects to the demonstrations of Donders and to my own proof because they are correct only for certain points on the cylinder. This objection must hold and I admit that Donders' and my own assumption in speaking of the refractive value of a cylinder, C, in a median, X, and in expressing it by C sin2 X is not justified by our knowledge that a ray of light is refracted by a cylinder only in a plane at right angles to its axis. I wrote my paper in 1803 and gladly use this occasion to admit the inferiority of my demonstration and that of Bonders. The same unwarrantable assumption, however, has been made again by Br. Harold Wilson in Knapp's Archive's for 1808 (Vol. 28).... This book of over two hundred pages discusses the portions of geometrical optics of especial interest to the student and practitioner of ophthalmology.... -"Annals of Ophthalmology: A Quarterly Journal and Review," Vol. 9 [1900]