Joule did fundamental research into work, heat, energy, and electrical resistance, and invented arc-welding. Dalton taught him for two important years. Easily his most important scientific friendship, close, collaborative, and life-long, was with Thomson, starting with a chance honeymoon meeting in Switzerland. Playfair was a Manchester colleague; they wrote some papers together, and Joule later sent him a supply of thermometers. Stokes, a correspondent, was early on converted to Joule’s theories; Tyndall however promoted his rival Mayer, the cause of personal friction. Helmholtz, visiting with Roscoe, was saddened by his decline.