For many years, heat was an insoluble mystery. The first step toward understanding the mystery came in the mid-1600s, when scientists began constructing the first thermometers. Once they began to realize that temperature was measureable, they determined that anything that could be measured could be controlled. So began the effort to design a device to govern the temperature of a system.

That effort culminated around 1660 with the invention of the thermostat. Named from the Greek words for "constant temperature," the thermostat was invented by Dutch scientist Cornelius Drebbel. His device, used to regulate the temperature within a duck-and chicken-egg incubator, was actually an elegant combination of several different technologies. Placed above a furnace, the incubator was surrounded by a water-filled jacket. Inside the incubator was a container of alcohol that would expand as it was heated--this expansion pushed down on a U-shaped tube filled with mercury, and...