Thermo-dynamics, name given to the modern science of the relation between heat and work, which has established two fundamental principles, that when heat is employed to do work, the work done is the exact equivalent of the heat expended, and when the work is employed to produce heat, the heat produced is exactly equivalent to the work done.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Therapeutæ * Thermopylæ