Measure For Measure: the Story of Imperial, Metric and Other Units.

ALEX HEBRA

Believe it or not, the United States is officially a metric nation. In 1893, the secretary of the treasury declared it so But the idea never caught on here, and we have clung to the pound, gallon, and mile. Those imperial units were introduced 300 years ago by the British, but that country long ago forgot them in favor of kilogram, liter, and meter. Hebra considers why this is so, as he, surveys these two systems of measurement, as well as countless other methods that people have devised to measure everything from a strip of cloth to the brightness of a candle to the sound at a rock concert. His approach, however, is far less anthropological than mathematical. Many equations come into play as Hebra explains the physics behind devices such as the Jefferson pendulum and the grease-spot photometer. He details, for instance, how a person on the ground can measure the height of a tall building and how Boyle's law defines the relationship of volume and pressure for a perfect gas. The book relates how units of measurement are applied in such fields as mechanical engineering, physics, optics, and astronomy. Johns Hopkins, 2003, 215 p., b&w illus., hardcover, $24.95.