Basic Refrigeration

Brief historical sketch of ,man-made, cold.
The teory of ice dates back as recorded history. While the stone Age caveman knew what ice was,there was no thought about using it to preserve food. Thousands of years later the Chinese learned that ice improved the taste of drinks. So they cut ice in winter,packed it with straw and chaff, and sold it during the summer.
The early Egyptians found that water could be cooled by placing it in porous jars on roof tops at sundown. The night breezes evaporated the moisture which seeped through the jars, making the water inside the jars cooler. The Greeks and Romans had snow brought down from mountain tops to cone-shaped pits which were lined with straw and branches and then covered with a thatched roof. As civilization advanced, people learned how to cool beverages and foods for enjoyment. This knowledge increased the use of ice and snow