333 Chapter 10 Adsorption Properties of Hair Trefor Evans TRI-Princeton Introduction In the small town of Chamonix at the base of the French Alps is a statue of the Swiss aristocrat, explorer, and scientist Horace-Bénédict de Saussure (1740-1799). de Saussure is perhaps most famously remembered for placing a bounty on Europe’s highest mountain, Mont Blanc, by offering a reward to the first person to reach its summit. As a result he is often considered the founder of modern day mountaineering but, among other accomplishments, he is recognized as an early pioneer in the fields of geology and meteorology. He enters our story as the inventor of the hair hygrometer. Modern day electronic equipment has since replaced this device but, for many years, de Saussure’s invention was the primary means for measuring the relative humidity of the atmosphere. Even today, the hair hygrometer remains a staple at high school science fairs, while also representing the workings within attractive German weather houses. The underlying mechanism relates to changes in environmental conditions causing an alteration in the dimensions of hair fibers. As the relative humidity rises, fibers swell in both the radial and longitudinal direction. These slight changes in length can then be exaggerated through the use of pulleys and levers to move a pointer, or to expel a small German herren from the weather house into