<Li> A smoke detector is a device that detects smoke and issues a signal . Most smoke detectors work either by optical detection or by physical process, but some of them use both detection methods to increase sensitivity to smoke . Smoke detectors are usually powered by battery while some are connected directly to power mains, often having a battery as a power supply backup in case the mains power fails . The first automatic electric fire alarm was co-invented in 1890 by Francis Robbins Upton and Fernando J. Dibble . Upton and Dibble were issued U.S. patent #436,961 . Upton was an associate of Thomas Alva Edison, although there is no evidence that Edison contributed to this invention . </Li> <P> 1891 Ferris wheel </P> <P> A Ferris wheel is a non-building structure, consisting of an upright wheel with passenger gondolas attached to the rim . Opened on June 21, 1893 at the Chicago World's Fair, the original Ferris Wheel was invented two years earlier by the Pittsburgh, Pennsylvania bridge - builder George Washington Gale Ferris Jr. in 1891 . </P> <P> 1891 Dow process </P>

What came first the ferris wheel or the teddy bear