The counting may be done electronically, usually in clocks with digital displays, or, in analog clocks, the AC may drive a synchronous motor which rotates an exact fraction of a revolution for every cycle of the line voltage, and drives the gear train.
Cady in He wrote: "It is not yet twenty years since there was found the art of making eyeglasses, which make for good vision The technology would eventually spread to Europe with one of the first recorded use of them at the Battle of Crecy by the English against French crossbowmen.
Suddenly Europeans had a useful tool for navigating the oceans of the world. Natural and herbal contraception has been used for millennia.
Meanwhile, the screw a stronger but harder-to-insert fastener is thought to have been invented by the Greek scholar Archimedes in the third century B. He also cites the overwhelming prevalence of quantitative accounting records among surviving historical fragments, from ancient Egypt to Nazi Germany.