Thermodynamics

—The branch of the theory of heat that treats relaof the tions between heat and mechanical work, especially as acting in a heat engine; as, the steam engine. This term is made from two Greek words, which signify, respectively, heat and power.; The first two laws of thermodynamics are as follows: (1) In the conversion of heat into mechanical energy, one unit of heat is lost for every 778 foot pounds of energy obtained; and conversely, in the production of heat by mechanical means, one unit of heat is obtained from_every 778 foot pounds of energy expended. (Joule.) (2) It is impo ible for a self-acting engine to convey heat from one body to another at a higher temperature without external aid. (Clausius.)