774 GEORGE GABRIEL STOKES. 



which had made such advances outside the country. Thus the men of 

 the period, in the middle of which came Stokes, had the advantage of 

 being trained by those who were thoroughly grounded in the old 

 methods, but who had spent time and energy in Avorking up and intro- 

 ducing the new. Neither was the intellectual activity of the pioneers 

 of the new movement confined to research in mathematics. Text- 

 books had been written setting forth the continental methods, and 

 translations of foreign works had been made. A classical tripos had 

 been established in 1824, but all candidates who went in for it were 

 required to have taken honors previously in mathematics — a rule 

 abolished in 1850. 



The mathematical jDower of Stokes l)egan to show itself immedi- 

 ately. His first paper was published the year after he took his de- 

 gree and the decade which followed was certainly the most fruitful of 

 his life in regard to the equality and quantity of the work which has 

 come directly from his pen. The Koyal Society Catalogue contains 

 the titles of over 50 papers printed Avithin this period, and many of 

 these are not only of far-reaching importance but mark the begin- 

 nings t)f his researches into almost every department of mathematical 

 physics — hydrodynamics, light, elastic solids, the mathematical ex- 

 pression of wave motion by Fourier's series, sound and conduction of 

 heat. iVIodest as he was concerning his own achievements, he thought 

 nearly all of these papers sufficiently good to l)e included in his col- 

 lected works, the first three volumes of Avhich cover this period alone. 

 To mention a few of the most important, we have the researches On 

 the Steady Motion of Incompressible Fluids and On the Theories of 

 the Internal Friction of Fluids in Motion, and of the Equilibrium 

 and Motion of Elastic Solids, with a Supplement, which together 

 constitute the complete foundation of the hydrokinetics of the present 

 day. In the paper On the P^ffect of the Internal Friction of Fluids 

 on the Motion of Pendulums, he considers and works out the effect 

 of viscosity on various kinds of motion. I)ee|)-sea waves and the soli- 

 tary waves are ver}^ fully treated in the memoir On the Theory of 

 Oscillatory Waves. But the theory of light was the subject in which 

 he seems to have been most willing to work. The two papers, On the 

 Dynamical Theory of Diffraction and On the Change of Kefrangi- 

 bility of Light, in the latter of which fluorescence* is described and 

 explained, would have alone sufficed to make his reputation. 



Two further papers. On the Critical Values of the Sums of Periodic 

 Series and On the Numerical Calculation of a Class of Definite Inte- 

 grals and Infinite Series, must be mentioned, not only because of their 

 great intrinsic value, but also because they show that the author was 

 i'igh( abreast of the developments in pure mathematics at that time 

 and that he was able to advance them and use them as an instrument 

 of research for the investigation of i)hysical ])i"()blems. 



