In 1865 the British Association created a committee, led by Pengelly, to fully explore the cave system over the course of fifteen years. It was Pengelly's party that discovered Robert Hedges' stalagmite inscription, and from the stalagmite's growth since that time deduced that human-created artefacts found under the formation could be half a million years old. Pengelly plotted the position of every bone, flint, and other artefact he discovered during the excavations, and afterward continued working with the Torquay Natural History Society until his death in 1892 at his home less than 2 km from the caves.