Today, we watch slaves reshaping Virginia. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

America's slave population leveled off at 250,000 before the Revolutionary War. Those slaves were heavily concentrated in eastern Virginia, where they outnumbered the free population three to two. America in general, but Virginia in particular, was strongly changed by this African presence.

Mechal Sobel's compelling book, The World They Made Together, tells us how this ethnic interweaving affected Colonial America. Think about the way we deal with time. The white Protestant population had the time-regulated mind of 18th-century rationalists. Time was elastic for the Africans. It stretched out in summer and shrank in winter. Time had different meanings in different activities. Heaven was slow and Hell was fast.

Thomas Jefferson was the quintessential Virginia rationalist. He fixated on time. It was something to be penny-pinched. Clocks ticked in every room of Monticello. A contemporary hymn caught that mood when it told us,

Thy precious time misspent, Redeem,
Each present day thy last esteem:

The slave majority had a lesson to teach these people. Before they were done, they'd laid an African rhythm on Virginian life.

But they did much more than that. The arts and crafts of the South reflect strong African influences. Techniques of African house-construction were carried into the new world. Colonial toys, dolls, quilt-patterns, musical instruments -- they all show African forms, viewpoints, and craftsmanship.

Slaves also held Christianity up to the light of their native belief in highly interactive gods. It made sense to them. They took it up with startling intensity. Negro spirituals were only the most visible part of what proved to be serious theological influence. And they turned the heat of their conviction on their white masters. One of Jefferson's slaves wrote to him when he was ill:

I was sorry to hear that you are so unwell ... but I hope as you have been so blessed in [your illness] that you considered it was God that done it and no one other ...

We're startled to see the slave of a United States president so openly invoking the ideas of St. Paul in calling him to repentance. But the institution of slavery, in such a uniformly mixed population, resulted in this sort of intimacy between blacks and whites. Thomas Jefferson showed curious ambivalence on the subject of slavery. And we're beyond being surprised when we learn that his death was announced by flying a white flag. White -- the African color of mourning.

By then, of course, our nation's culture had been taken very far from England. By then we'd been significantly -- and permanently -- reshaped in the direction of African views and values.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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Sobel, M. The World They Made Together. Princeton, NJ: Princeton University Press, 1987.