A flying buttress is a specific form of buttressing most strongly associated with Gothic church architecture. The purpose of any buttress is to resist the lateral forces pushing a wall outwards (which may arise from stone vaulted ceilings or from wind-loading on roofs) by redirecting them to the ground.
In The Lost World, the flying buttress of Gothic cathedrals is one of the subjects that Richard Levine sends Arby and Kelley to Xerox papers on at various Stanford libraries.
