a website collaboration between Science Service and the Smithsonian Institution

1938 - the operator rotates each jewel painstakingly under a microscope

SAPPHIRES

CD 1966048 E&MP30.004

Electric Meters

May 18, 1938

The cupped-out bearings in each sapphire must be exact, since the wheels turn on pivots ten times as sharp as a sewing needle, so the operator rotates each jewel painstakingly under a microscope. 





Original Caption by Science Service
Westinghouse



National Museum of American History

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