JOSEF STEFAN AND LUDWIG BOLTZMANN 357 



scientific papers already commenced, and these gradually 

 covered all branches of physics. This versatility and the 

 extraordinary thoroughness with which he undertook every- 

 thing, also made Stefan very successful in the scientific 

 education of teachers at that period, when, after himself 

 having taught for seven years in a school, he was called at the 

 age of twenty-five to be professor of physics at the university 

 of Vienna, where he then remained for thirty-three years, 

 until his death. 



His lectures were of unusual clarity and perfection. As 

 regards his experimental labours, the difficult investigations 

 of the heat conductivity of gases deserve particular men- 

 tion, since they afforded a new means of testing and con- 

 firming the kinetic theory of gases, which had become im- 

 portant in so many directions; up till then no sufficiently 

 clear experiments and exact measurements had been made 

 by anyone regarding the heat conductivity of gases. His 

 mode of life was extremely simple and quiet. He was a 

 silent man, but always anxious to assist honest scientific 

 endeavour, regarding this as a self-evident patriotic duty. 

 Boltzmann and Hasenohrl were his pupils. He hardly ever 

 went to scientific congresses, just as little as did Bunsen in 

 his later days. His nature became more light hearted after 

 he married, at the age of fifty-six. But he died only two 

 years later after a short illness. 



Ludwig Boltzmann was born in Vienna, and there studied 

 mathematics and physics with Stefan, whose assistant he 

 became. At the age of twenty-five he received a call 

 as assistant professor of physics to the university of Graz, 

 and shortly afterwards he became professor of mathe- 

 matics at the university of Vienna. After he had carried 

 out interesting experimental work concerning the dielec- 

 tric constant of gases, in which a certain conclusion from 

 Maxwell's theory was tested, he was called in 1876 to Graz 

 as the chief representative of physics, where he remained 



