"There is a fullness of time when men should go, and not oc- cupy too long the ground to which others have a right to ad- vance."
So wrote Thomas Jefferson after he had finished his second term at the White House and returned to Monticello, his Vir- ginia estate. At 68, the third president had put public life far be- hind him. He was now engaged in other interests-science, architecture, even the study of Greek and (with "great avidity") of mathematics.
As usual, Jefferson...