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 who silently acquiesced when his discoveries were attributed to others, and allowed his name to perish entirely from Cambridge tradition.

A few years before Green published his first paper, a notable revival of mathematical learning swept over the University; the fluxional symbolism, which since the time of Newton had isolated Cambridge from the continental schools, was abandoned in favour of the differential notation, and the works of the great French analysts were introduced and eagerly read. Green undoubtedly received his own early inspiration from this source, but in clearness of physical insight and conciseness of exposition he far excelled his masters; and the slight volume of his collected papers has to this day a charm which is wanting to the voluminous writings of Cauchy and Poisson. It was natural that such an example should powerfully influence tho youthful intellects of Stokes—who was an undergraduate when Green read his memoir on double refraction to the Cambridge Philosophical Society—and of William Thomson (Kelvin), who came into residence two years afterwards.

In spite of the advances which were made in the great memoirs of the year 1839, the fundamental question as to whether the aether-particles vibrate parallel or at right angles to the plane of polarization was still unanswered. More light was thrown on this problem ten years later by Stokes's investigation of Diffraction. Stokes showed that on almost any conceivable hypothesis regarding the aether, a disturbance in which the vibrations are executed at right angles to the plane of diffraction must be transmitted round the edge of an opaque body with less diminution of intensity than a disturbance whose vibrations are executed parallel to that plane. It follows that: when light, of which the vibrations are oblique to the plane of