One midsummer’s morning, c. 1820, William Butterfield opened the door to the Wells, a healing spring on the edge of Ilkley Moor. He was startled to find a band of little creatures dressed in green from head to foot, who were noisily disporting themselves in the water. As he watched, they scurried over the eight-foot-high wall, and disappeared. Is there any way to determine exactly what William Butterfield saw that morning? Were they insects, lizards, or, as William believed, fairies? Simon and Chris investigate. 

Source: http://www.strangehistory.net/puca-ghost-witch-and-fairy-pamphlets/the-witches-and-fairies-of-nineteenth-century-ilkley/