How did Henry Cavendish explain heat in his mechanical theory?

Working within the framework of Newtonian mechanism, Henry Cavendish rejected the contemporary caloric theory, which posited that heat was a material substance or fluid. Instead, he explained heat as the result of the motion of matter.1

In the late 1780s, Cavendish developed a general theory of heat that was both mechanical and mathematical in nature. This theory included the principle of the conservation of heat—an early understanding of the conservation of energy—and even incorporated the concept of the mechanical equivalent of heat, though he did not use that specific label. His work demonstrated a sophisticated, early commitment to a dynamical view of thermal phenomena, contrasting with the material theories prevalent among many of his peers.1