  Fans and critics of Boltzmann's work alike agree that he pioneered much of the approaches currently used in statistical physics, but also that he did not leave behind a unified coherent theory. His scientific papers, collected in Wissenschaftliche Abhandlungen, contain more than 100 papers on statistical physics alone. Some of these papers are forbiddingly long, full of tedious calculations and lack a clear coherent structure. Sometimes, vital assumptions, or even a complete change of approach, are stated only somewhere tucked away between the calculations, or at the very last page. Even Maxwell, who might have been in the best position to appreciate Boltzmann's work, expressed his difficulty with Boltzmann's longwindedness (in a letter to Tait, August 1873; see Garber, Brush, and Everett 1995, 123).[6] But not all of his prose is cumbersome and heavy-going. Boltzmann at his best could be witty, passionate and a delight to read. He excelled in such qualities in much of his popular work and some of his polemical articles.