In 1758, Benjamin Franklin demonstrated that evaporation of volatile compounds, such as ether, could cause the object from which the evaporation was occurring to drop below room temperature. During one of his experiments, he managed to lower the temperature of a thermometer from 64ºF down to 7ºF. Today, the evaporation of refrigerant compounds is an essential process in millions of cooling systems.
Prior to electricity, there was little relief from oppressive summer heat and humidity. Cross ventilation through open windows provided some solace if a breeze was present but remained unable to lower oppressive humidity.