This is the second volume of a two-volume collection of over 100 articles spanning half a century of work by the late Soviet scientist Yakov Borisovich Zeldovich. The breadth and depth of Zeldovich's work is staggering. Author of over twenty books and more than 500 scientific articles, he made fundamental contributions in chemical catalysis and kinetics, combustion and the hydrodynamics of explosive phenomena, nuclear chain reactions and nuclear energy, the physics of elementary particles, and the large-scale structure of the universe and cosmology. The importance of this collection lies not only in its documentary value as a collection of key scientific works by a man of genius. Zeldovich himself considered his most valuable role to be that of a teacher, to convey to young scientists the how of science. The author of several excellent textbooks on topics ranging from elementary mathematics to advanced methods of mathematical physics, he saw this collection of works, enlarged from the original Russian edition, as a contribution to that end. Commentaries by the author and the editors are included with each paper serving to enhance both the historical and the pedagogical value of this edition. The passing of Yakov Borisovich Zeldovich in December, 1987, was a loss felt deeply by scientists all over the world. This collection of his works serves as a tribute to him as a man, a scientist, and, above all, a teacher. Originally published in 1993. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.