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**

# § 12. George Green

We return to the subject of theoretical physics. It was the good fortune of the Cambridge school to produce, in the Victorian period, some of the greatest physicists of the century. The university course for a degree, at that time, involved a study of the elements of nearly all the branches of mathematics then read; and, thus, its graduates were exceptionally well equipped for discussing physical problems from the mathematical side. Among these physicists, we here mention briefly the work of George Green, (Sir) George Stokes, (Sir) William Thomson afterwards lord Kelvin, and Clerk Maxwell. To their credit, be it said, they all treated symbols and formulae as servants and not as ends in themselves.

George Green was a self-educated man, who came to Cambridge in middle life and took his degree in 1837, unfortunately for science dying four years later. In 1828, he introduced the idea of the potential, representing the work which must be done to move a unit of mass from infinity to its position. In this memoir is established the celebrated formula, connecting surface and volume integrals, which forms a fundamental proposition in the theory of attractions. Green wrote on various physical questions, notably on the motion of waves in a canal, and the deduction of the geometrical laws of sound and light from the undulatory theory. In these writings, he showed remarkable physical insight in the applications of his analysis. His memoirs on the propagation of light in a crystalline medium, published in 1839, rest on the assumption that the ether in a crystal resembles an elastic solid unequally pressed in different directions by unmoved ponderable matter—a conception which, later, was to lead to remarkable developments. Few writings have been more fruitful than those of Green. They led MacCullagh and Cauchy to revise their theories of optics, and they profoundly impressed Stokes and Kelvin, whose work we now proceed to describe.