Since it was discovered in 1852, the fascinating pyramid of rock that is Mount Everest has haunted the dreams of generations of explorers. From the expeditions of the 1920's, which provided the first blood offerings to the deity of the snows, to the attempts that brought Hillary and Tenzing to the top in 1953, to the "high altitude tourism" that now attracts roped parties of mountain climbers from every corner of the world.