Science: Assist by Archimedes

In New York City’s Bronx Zoo, Superintendent Quentin Schubert and Executive Secretary John Tee-Van pondered the problem of how to weigh Pete, a 43-year-old hippopotamus. Scales were obviously out of the question. Suddenly they remembered Archimedes.

His principle*made it all easy. In the hippo’s tank they rigged up a contraption consisting of a hollow tube (stuck vertically in the water) enclosing a float attached to a moving arm arranged to swing around a marked scale. (On the basis of Archimedes’ principle, the markings had been calibrated to register the weight of the water displaced, easily calculated from water’s known weight by volume: 62.4 Ibs. per cu. ft.)

When Pete plunged in, the rising water raised the float, which moved the arm, which pointed on the scale. Pete’s weight: 3,800 Ibs.

*While brooding in a public bath over a question posed to him by King Hiero of Syracuse—how to determine whether the King’s crown was made of pure gold—Archimedes hit on the answer, jumped up, ran home naked, shouting “Eureka!” (I have found it.) The solution: by weighing the crown under water, Archimedes easily determined how much heavier it was than water, compared the result with the known specific gravity of pure gold. A floating body, he went on to show, displaces its own weight in water.