Human hair was used to operate an electric fog bell 100 years ago. The logic behind that hair use was that hair stretches when damp and tightens when dry. When the atmosphere was moist, the hair would stretch and raise the alarm.
Hair Made to Ring Bell
The fact that human hair stretches under moisture has been applied by the United States Lighthouse Service in the operation of the newest form of electric fog bell, which is made to ring automatically when the atmosphere reaches a certain degree of dampness.
A strand of several hundred hairs is stretched between two supports, and on the strand is a link. As the air gets moist, as in a fog, the hair stretches, the link is lowered and makes an electrical contact which starts a half-horsepower motor. This operates the fog-bell striker.
As the fog disappears, the link is raised and the fog bell stops.
Source: Evening star. (Washington, D.C.), 28 Dec. 1924.
