An Aden civilian crouching in terror as British soldiers threaten him during Arabian demonstrations in Crater. (Photo by Express Newspapers/Getty Images). 1967

A worker pauses for a sandwich, resting on a girder during the construction of a skycraper. (Photo by Hulton Archive/Getty Images). Circa 1930

Three workers demonstrating the different types of gas masks used in mine rescue work. (Photo by Fox Photos/Getty Images). December 1925

The Burney, a new streamlined car on the London streets, designed by Sir Denniston Burney who was responsible for the design of the R100 (R 100) airship. The engine is in the rear. (Photo by Topical Press Agency/Getty Images). 15th September 1930

A member of Libyan forces allied with the U.N.-backed government fires a weapon on a pickup truck during a battle with Islamic State militants in Giza Bahreya, in Sirte, Libya October 27, 2016. (Photo by Hani Amara/Reuters)

A walker has left a handprint on a snow- covered tree trunk on Grosser Feldberg mountain in the Taunus mountain range, Germany, 16 January 2017. (Photo by Frank Rumpenhorst/DPA)

A weapon is being destroyed during an exercise to disable seized weapons in Caracas, Venezuela August 17, 2016. (Photo by Marco Bello/Reuters)

A news crew runs from flames southeast of Middletown, Calif., on Tuesday, September 15, 2015, as winds kick up the Valley fire. (Photo by Wally Skalij/Los Angeles Times/TNS)