The Cambridge History of English and American Literature in 18 Volumes (1907–21). Volume XIV. The Victorian Age, Part Two. VIII. The Literature of Science. § 11. Sir George Darwin. We have already briefly described Adams’s investigations in mathematical astronomy, and, perhaps, we may here add a word or two on the researches of (Sir) George Howard Darwin, also of Cambridge, who investigated the form taken by a rotating viscous mass of matter, and showed that, in the early history of the solar system, the moon arose from a portion of the earth thrown off (when the latter was in a plastic condition) through its increasing velocity of rotation. Later, he demonstrated that the moons of the other planets could not have originated in the same way. He wrote at length on the theory of tides. He also worked at the problem of three bodies, investigating, by lengthy arithmetical methods, possible stable forms of periodic orbits of one body, moving under the attraction of two other bodies.   23   With observational and practical astronomy we are not here concerned; but we may add that the results of the astronomical discoveries of the Victorian period were made familiar to the English speaking world by the popular treatises and lectures of Sir Robert S. Ball whom we have already mentioned, and by various works by Miss A.M. Clerke.   24   Mention may here be made, also, of two great teachers of the Victorian age, to wit, William Hopkins, and Edward John Routh, under whom many generations of Cambridge mathematicians were educated, and to whom the predominance in Britain, throughout the period here treated, of the mathematical school of that university is largely due. Of more recent English writers on pure mathematics, some have devoted themselves to higher analysis, expecially differential equations, differential geometry and the theory of functions; other have followed continental initiative in discussing the fundamental principles and philosophy of mathematics.   25