Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/52

 preface I have written," Kelland says, "without consulting my colleagues, as I am thus enabled to say what could not otherwise have been said, that mathematicians owe a lasting debt of gratitude to Prof. Tait for the singleness of purpose and the self-denying zeal with which he has worked out the designs of his friend Sir William Hamilton, preferring always the claims of the science and of its founder to the assertion of his own power and originality in its development. For my own part I must confess that my knowledge of Quaternions is due exclusively to him. The first work of Sir William Hamilton—Lectures on Quaternions—was very dimly and imperfectly understood by me and I dare say by others, until Prof. Tait published his papers on the subject in the Messenger of Mathematics. Then, and not till then, did the science in all its simplicity develop itself to me."

Tait had now co-operated with Steele in writing Dynamics of a Particle, with Thomson in a Treatise on Natural Philosophy, and with Kelland in the Introduction to Quaternions. There was still a fourth literary partnership to follow; this time with Balfour Stewart, professor of physics at the Owens College, Manchester. In 1875 a volume called The Unseen Universe, having as a sub-title "Physical Speculations on a Future State" appeared anonymously; but to a physicist it was evidently inspired by Tait's Sketch of Thermodynamics and Stewart's book The Conservation of Energy. It was asserted in the Academy that Tait and Stewart were the authors; and a subsequent edition appeared with their names on the title page. It was to most people a matter of surprise that one who had been denouncing metaphysics in season and out of season, should turn out to be part author of a book described as "physical speculations on a future state." Did not Kant say that the three problems of metaphysics are God, freedom, and immortality? What is metaphysics but speculation based upon physical science concerning things which can never be reached directly by the methods of physics? The Unseen Universe was metaphysics of the best or worst (however you may view it) kind; it was full of Carnot's reversible engine, the