ABSTRACT
Ancient Hebrews, Greeks, and Romans placed large amounts of snow into storage pits dug into the ground and insulated it with wood and straw. By 500 b.c. the Egyptians and Indians were using evaporative cooling. They filled earthen jars with boiled water and put them on their roofs, thus exposing the jars to the night’s cool air. By 1550, lower temperatures were achieved by adding chemicals such as sodium nitrate to water. In 1748, William Cullen was using volatile liquids such as ethyl ether boiling in a partial vacuum.
