thinning Martian atmosphere is artificially replenished from an "atmosphere plant." It is a world with clear territorial divisions between White-, Yellow-, Black-, Red-, and Green-skinned races. Each has particular traits and qualities, which seem to define the characters of almost every individual within them. Burroughs's concept of race in Barsoom is more similar to species, rather than ethnicity. Technology The Red Martians of Barsoom have fliers operating with a form of anti-gravity. Thuvia, Maid of Mars is notable in that John Carter's son, Carthoris, invents an apparent precursor of the autopilot (decades before an actual device was perfected). The mechanism allowed the pilot to reach any destination on Barsoom, although it required the pilot to keep the craft pointed in the right direction. Upon arrival, the mechanism also lowered the flier to the ground. Carthoris' flier was also equipped with an anti-collision device, which detected obstacles and automatically steered around them. Themes While Burroughs is generally seen as a writer who produced work of limited philosophical value, Burroughs wrote two Barsoom novels that appear to explore, or parody, the limits of excessive intellectual development at the expense of bodily or physical existence. Thuvia, Maid of Mars, with its depiction of the Lotharians is the first. The Lotharians have mostly died out. They had been fleeing from the attacks of Green Martians, during which most of them were killed (including all women and children), when they found a defensible location and came to a dramatic realization that the mind is everything, and hence developed advanced telepathic powers including the ability to create phantom bowmen to combat their Green Martian adversaries. Such is the detail of their power of imagination that the bowmen even appear to die in combat, and the Green Martians are killed by their arrows. A Lotharian, Jav, explains to the protagonist, Carthoris, that the illusion is only maintained by the belief of the Green Martians. If they knew the truth it would not be effective. The Lotharians also maintain the illusion of a functioning, normal Barsoomian society through powerful telepathic projections. They have formed two factions, which appear to portray the excesses of pointless intellectual debate - one faction, the realists, believes in imagining meals to provide sustenance, another, the , believes in surviving without eating. The Chessmen of Mars is the second example of this trend. The Kaldanes have sacrificed their bodies to become pure brain, but