  As we have seen, the 1877 papers introduced some conceptual shifts in Boltzmann’ approach. Accordingly, this year is frequently seen as a watershed in Boltzmann's thinking. Concurrent with that view, one would expect his subsequent work to build on his new insights and turn away from the themes and assumptions of his earlier papers. Actually, Boltzmann's subsequent work in gas theory in the next decade and a half was predominantly concerned with technical applications of his 1872 Boltzmann equation, in particular to gas diffusion and gas friction. And when he did touch on fundamental aspects of the theory, he returned to the issues and themes raised in his 1868–1871 papers, in particular the ergodic hypothesis and the use of ensembles. 