he dropped lightly over the edge of the roof , landed on a ridge , ran easily across the sleeping building , jumped a narrow gap on to the tiled roof of the young men 's reformed-cultists-of-the-ichor-god-bel-shamharoth association gym , jogged gently over the grey slope , swarmed up a twelve foot wall without slowing down , and vaulted on to the wide flat roof of the temple of blind io .