Unamuno, the Spanish philosopher, tells about the Roman aqueduct at Segovia, in his native Spain. It was built in 109 A.D. For eighteen hundred years, it carried cool water from the mountains to the hot and thirsty city. Nearly sixty generations of men drank from its flow. Then came another generation, a recent one, who said, "This aqueduct is so great a marvel that it ought to be preserved for our children, as a museum piece. We shall …