A brief look at some older heating methods brings interesting new applications.
In the beginning, there was cold water-and people didn't bathe much. They masked body odor with perfumes and oils or just went around smelly. Even as recently as the turn of the century, running hot water was a luxury. It was available only to those who were well off. In the United States today, a personal supply of hot water is thought of as a necessity, right up there with food and shelter. (Just try going without it.)
Over time, people have heated water in many ways. A brief look at some of these methods offers an interesting perspective and demonstrates how some of these older and now unused techniques could have applications today.