The 308 letters in this volume cover a critical period in Tyndall’s personal and scientific lives. The volume begins with the difficult ending of his relationship with the Drummond family, disputes about his work in glaciology, and his early seminal work on the absorption of radiant heat by gases. It ends with the start of his championship of Julius Robert Mayer’s work on the mechanical equivalent of heat. In between, Tyndall carefully establishes his own priority for his work on radiant heat, and he accepts the position of professor of physics at the Government School of Mines. The lure...