This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

Girls in Han costumes pose for a photo with blooming cherry blossoms at Yuyuantan Park during Qingming Festival holiday on April 4, 2022 in Beijing, China. Qingming Festival, also known as Tomb Sweeping Day, falls on April 5 this year. (Photo by Zhao Naiming/VCG via Getty Images)

This picture taken on April 25, 2022 and released from North Korea's official Korean Central News Agency (KCNA) on April 26 shows a military parade to celebrate the 90th anniversary of the founding of the Korean People's Revolutionary Army at Kim Il Sung Square in Pyongyang. (Photo by KCNA via KNS/AFP Photo)

“This is the heart-stopping moment a photographer came within inches of a young cheetah when it stuck its head through her sun roof. Australian Bobby-Jo Clow, 31, was on safari in Tanzania when the juvenile started heading towards her Landrover with his sibling. She snapped away as the young male dangled its paws in front of her face and smelt her hair before its mother called it away into the wilds of the Serengeti National Park. But not until Bobby-Jo, a full-time elephant keeper at a Tanzanian Zoo, had leaned forward enough to capture the perfect shot, causing the cheetah to hiss and bare its teeth”. – Caters News. (Photo by Bobby-Jo Clow/Caters News)

Two dancers pass each other as they compete in a heat during the All Scotland Championships in Irish Dancing at the Royal Concert Hall in Glasgow, Scotland. The championships attract over 2000 dancers from more than 300 dance schools, from countires such as North America, South Africa, Australia and Russia. (Photo by David Moir/Reuters)

Jacob's Well is a perennial karstic spring in the Texas Hill Country flowing from the bed of Cypress Creek, located northwest of Wimberley, Texas. The twelve foot (four meter) diameter mouth of the spring serves as a popular swimming spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob's Well cave descends vertically for about thirty feet (ten meters), then continues downward at an angle through a series of silted chambers separated by narrow restrictions, finally reaching a depth of one hundred and twenty feet (forty meters). Until the modern era, the Trinity Aquifer-fed natural artesian spring gushed water from the mouth of the cave, with a measured flow in 1924 of one hundred and seventy gallons per second (six hundred and forty liters per second) discharging six feet (two meters) into the air. The spring is the greatest source of water recharging the Edwards Aquifer.

In this photo taken Tuesday, October 14, 2014, skulls and bones are stacked at the Catacombs in Paris, France. The subterranean tunnels, stretching 2 kilometers (1.24 miles), cradle the bones of some 6 million Parisians from centuries past and once gave refuge to smugglers. The site used to close at 5 p.m., but is now staying open until 8 p.m. The change is mainly aimed at allowing more people to visit and reducing long lines, since it can only hold a limited number of people at a time and visits can't be reserved in advance. (Photo by Francois Mori/AP Photo)

If we were to burn NH4Cr2O7 with HgSCN in the Dark Ages in Europe and show it to anyone, it is us who would be burning next on a fiery cross of Inquisition. And it’s no wonder, since this experiment produces a truly marvelous result. At first, as you ignite the mixture of NH4Cr2O7 and HgSCN, all you can see is that it is slowly burning with a reddish flame. After a while, however, a crater is formed in the middle of the burning pile, and then, suddenly, tentacle-like appendages start sprouting from the burning mixture. And you can almost hear the scream of the mad occultist – “Come forth, Kraken! Come forth!” But of course, this is simply a chemical reaction that is called the "Pharoah's Serpent". It was also often sold in firework stores until people realized that it was toxic.