The Professor determines that a manned space craft will pass over the island, and attempts to fashion a telegraph machine. When that fails, the Castaways try to spell out SOS using burning logs as a rescue signal, but Gilligan catches fire and runs into the logs, causing them to spell out SOL, the name of one of the astronauts! Blooper watch: as Gilligan is lighting the logs, you can see his pants smoking before he backs up into the flaming logs! (thetvdb.com)