Calhoun said that for a long time he had believed that the dispute over slavery -- if not settled -- would end in disunion.

VOA: special.2009.03.26

Over long periods of time, these small changes result in the creation of new species.

VOA: special.2009.12.01

He thought that this was evidence that the bottom of the ocean had been lifted up by powerful geological forces over long periods of time.

VOA: special.2009.02.25

So,to get a sense of what the regional moisture patterns have been, dryness and wetness over such a long period of time in great detail, I would call it a kind of victory for paleoclimate science."

VOA: special.2010.05.25