Gay-Lussac is best known for his chemical work but also made important contributions to other physical sciences and technology. This is the first work to examine critically both the scientific work and the man behind it. Joseph Louis Gay-Lussac (1778–1850) lived through three revolutions in France and his life reflected the social transformations taking place around him. His education and early progress in science depended on the Revolution of 1789 and on the patronage of the chemist Berthollet, a close associate of Napoleon Bonaparte. Gay-Lussac may be seen as the first ‘professional’ scientist and indeed, throughout the book, Professor Crosland emphasises that he knew how to use his science to solve practical problems and was able to profit considerably from this application.