Apergy is a fictitious form of anti-gravitational energy described by Percy Greg in his sword and planet novel Across the Zodiac.
It is also used by John Jacob Astor IV in his 1894 science fiction novel, A Journey in Other Worlds.
Apergy can also be found in an 1888 article by Clara Jessup Bloomfield-Moore, called "Some Truths About Keely". In it, apergy is used to describe the latent force John Keely harnessed, by using frequency to release the latent force found within all atomic matter.
In Chris Roberson's short story "Annus Mirabilis" from the second volume of Tales of the Shadowmen, Doctor Omega and Albert Einstein investigate apergy. Apergy is also mentioned in the Warren Ellis comic Aetheric Mechanics, as being generated by Cavorite technology from The First Men in the Moon.
In S. P. Meek's short story "Cold Light", which appeared in Astounding Stories of Super-Science, March 1930[1], apergy is mentioned as the opposite force of gravity.