Heat pump the brand name Freon, a trademark of DuPont. Its manufacture is now banned or severely restricted by the Montreal Protocol of August 1987 because of the damage that CFCs cause to the ozone layer if released into the atmosphere. One widely adopted replacement refrigerant is the hydrofluorocarbon (HFC) known as R-134a (1,1,1,2-tetrafluoroethane). Heat pumps using R-134a replaced R-12 (dichlorodifluoromethane) and have similar thermodynamic properties but with insignificant ozone depletion potential and a somewhat lower global warming potential. Other substances such as liquid R-717 ammonia are widely used in large-scale systems, or occasionally the less corrosive but more flammable propane or
The Horse that Lost its Liberty (1484) under the title “Of the hors, of the hunter and of the hert” as teaching the moral given by Aristotle that "None ought to put hym self in subiection for to auenge hym on other". Samuel Croxall cites Horace’s conclusion that one should never yield one’s liberty to another for reasons of avarice. The fable was told as “The horse seeking vengeance on the stag ("Le cheval s'étant voulu venger du cerf") in La Fontaine's Fables and ends on the reflection that without personal liberty all other purchases are valueless: The alternative version of the fable concerns a boar