Migrants react after boarding the Migrant Offshore Aid Station (MOAS) ship MV Phoenix some 20 miles (32 kilometres) off the coast of Libya, August 3, 2015. Some 118 migrants were rescued from a rubber dinghy off Libya on Monday morning. The Phoenix, manned by personnel from international non-governmental organisations Medecins san Frontiere (MSF) and MOAS, is the first privately funded vessel to operate in the Mediterranean. (Photo by Darrin Zammit Lupi/Reuters)

St Louis County police officers arrest an anti-police demonstrator in Ferguson, Missouri August 10, 2015. Dozens of protesters were arrested on Monday afternoon after blocking rush-hour traffic on Interstate 70 a few miles (km) from Ferguson, Missouri, during demonstrations over the police shooting of an unarmed black man a year ago, according to a Reuters witness. (Photo by Lucas Jackson/Reuters)

Firefighters attempt to put out a fire at an abandoned building with the protection of St. Louis City Police in St. Louis, Missouri August 19, 2015. Police fatally shot a black man they say pointed a gun at them, drawing angry crowds and recalling the racial tensions sparked by the killing of an unarmed African-American teen in nearby Ferguson, Missouri, just over a year ago. (Photo by Lawrence Bryant/Reuters)

Photographer Carlos Barria holds a print of a photograph he took in 2005, as he matches it up at the same location 10 years on, in Lafitte, south of New Orleans, United States, August 16, 2015. The print shows Tyler Teal cleaning up his home, September 14, 2005, after Hurricane Katrina struck. In 2005, Hurricane Katrina triggered floods that inundated New Orleans and killed more than 1,500 people as storm waters overwhelmed levees and broke through floodwalls. (Photo by Carlos Barria/Reuters)

Revellers celebrate "Ash Monday" by participating in a colourful "flour war", a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter,in the port town of Galaxidi, some 215 km (134 miles) north west of Athens, March 18, 2013. The revellers "fight" by throwing coloured flour, charcoal dust and powder painting until they essentially run out of supplies. (Photo by Yannis Behrakis/Reuters)

A group of Ashkenazi jews in Jerusalem. (Photo by Hulton Archive/Getty Images). Circa 1885

Dried and shrivelled corpses, some fully clothed and some in coffins, line the wall of a vault of the Pantheon Cemetery on the summit of Cerro del Trozado in Mexico. They were removed from the crypts because of non-payment of cemetery fees. The hot dry air stopped the bodies from rotting. Most of them were placed here between the turn of the century and WW I. (Photo by Three Lions/Getty Images). Circa 1955

A protester wears a pig mask as he marches through the streets of downtown Vancouver with thousands of people participating in the Occupy Vancouver protest on October 15, 2011 in Vancouver, British Columbia, Canada. Thousands of people are taking to the streets in cities across the world today in demonstrations inspired by the Occupy Wall Street protest in New York City. An estimated 2,000 people participated in the Vancouver occupation. (Photo by Jeff Vinnick/Getty Images)