A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

A child attends a training session in a swimming pool on July 10, 2007 in Wuhan of Hubei Province, China. (Photo by China Photos/Getty Images)

Brick-carving featuring Tang Dynasty (AD 618-907) maids performing musical instruments is seen at the Chinese Music History Museum in Xian University of Architecture and Technology on September 27, 2008 in Xian of Shaanxi Province, China. (Photo by China Photos/Getty Images)

American soldiers leaping from an armoured personnel carrier during exercises in Korea, 17th March 1954. (Photo by Three Lions)

Monsoon thunderstorm in Sierra Vista, Arizona. 9 Sept, 2011. (Photo by Steven Maguire)

A woman participates in the “Carnaval na Central” block party in Rio. (Photo by Felipe Dana/Associated Press)

“Monorail Subway, Capitol To Senate. The Car. Senators Swanson And Townsend As Passengers, 1916”. (Photo by Harris & Ewing Collection). (Please click to enlarge)