682 Biographical Memoirs followed in rapid succession,and this may well be regarded as one of the most productive periods in his career. All these investigations on elastic stability showed that only the simplest cases could be solved rigorously.This led Timoshenko to develop an approxi- mate method of solution based on a comparison of strain energies of a system in its initial and buckled shapes.The method was similar to that used by Rayleigh for approximate calculations of frequencies of natural vibration and again shows the influence of Rayleigh's book on Timoshenko's work.This was the first time that the so-called Rayleigh-Ritz method'had been applied to problems in the field of stability.This ability to see that certain ideas developed for work in one area could be transferred to another and made to yield rich results was characteristic of many of Timoshenko's contributions.The results of this work won Timoshenko the Jourawsky prize,awarded once every ten years for the best paper on structural mechanics.It was later translated into French and published in the Annales des Ponts et Chaussees in 1913.It had great influence on further developments in the field of elastic stability. In 1906,when he was only 28 years old,Timoshenko took part in the open competition for a professorship at Kiev Polytechnic.He received word in November that he had been selected to the professorship in strength of materials. He began his lectures in this subject in January 1907.It was at this time that he developed the technique of beginning a course with a discussion of the simplest cases and only gradually building up to full generalizations.This was contrary to the customary procedure of beginning with a general discussion of stress and strain in three dimensions and gradually working down to o =P/A. It proved so successful that in subsequent years of teaching he always used this approach in his classes;it was much appreciated by students.After developing the course in strength of materials,Timoshenko expanded his notes into a textbook on the subject,which first appeared in 1911.This was the first of his many textbooks on applied mechanics. In addition to the work on the application of energy methods to stability problems already discussed,Timoshenko also developed at.this time some valuable applications of normal coordinates to the solution of problems of bending of beams and plates.This was also extended to cases of combined bending and compression or tension and to forced vibrations of beams.This work is described in a paper,Etude de la flexion des barres,Annales des Travaux de Belgique,1914,and another,Erzwungene Schwingungen prismatischer Stabe,Zeitschrift fuir Mathematik und Physik,1911. In 1909,Timoshenko was elected dean of the civil engineering school at Kiev Polytechnic.This promotion to administrative levels not only interfered with his teaching and scientific work but was also the forerunner of serious trouble for him.There had been considerable political unrest and student demonstra- tions some six years earlier which had necessitated the closure of all institutions of higher learning for several months.The institutions were reopened in the autumn of 1906 after various revolutionary demands had been met;these including the granting of a constitution,the convocation of a State Duma and a