In 1824, the French physicist Nicolas Léonard Sadi Carnot scientifically established the thermodynamic theory of idealized heat engines. This highlighted the shortcoming of these pioneering designs, whereby they needed a compression mechanism to increase the difference between the upper and lower working temperatures and potentially unlock sufficient power and efficiency. Gasoline was not used for internal combustion engines until 1870 when carburetors were invented to convert non-combustible liquid fuels into a combustible gaseous mixture form.