If you think issues of uncleanness are limited to the ancient world, consider this cover story headline last year from an issue of U.S. News World Report: "The Future of Water: Costly - Dirty - Sc...
Unamuno, the Spanish philosopher, tells about the aqueduct built by the Romans in Segovia in 109 A.D. For 1800 years, that aqueduct carried cool water from the mountains down to the hot, thirsty city....