Today, a new look at an old fire. 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.

The great Chicago fire began around nine on the windy Sunday evening of Oct. 8th, 1871. It didn't burn itself out until Monday night. Rainfall had been only 28 percent of normal that summer, and Chicago's population had recently grown by a factor of ten.

Thirty years earlier, the modern balloon-frame house had come out of Chicago. That's the wooden structure with light joists and cross-members that we use in houses today. Chicago had become an overcrowded, wood-built, bone-dry city with a poor fire department.

The fire destroyed over three square miles of city, killed 250 people, and left 100,000 homeless. If one thing hadn't started the fire, another would've. But, still, we wonder what did start it.

My 1970 Encyclopaedia Britannica says the cause was unknown. My 1897 Britannica says the cause was an overturned lamp. When I was young, the great urban legend told how the fire began when Mrs. O'Leary milked her cow, and the cow kicked over her lantern.

Now Richard Bayles, who works for the Chicago Title Insurance Company, has gone back into his company's old files looking for Mrs. O'Leary. He found that she lived in a small rear house off Dekoven Street. Behind her house was a barn where she kept five cows. She sold milk to the neighborhood. Bayles has gone through testimony from the hearing after the fire.

Pegleg Sullivan, a young man with a wooden leg, testified he'd been on the far side of Dekoven Street and seen fire break out in the O'Leary barn -- nothing about Mrs. O'Leary or cows kicking lanterns. Sullivan had a lot to say about that night. He told how he'd run across the street to the barn and released the animals.

But old insurance maps show a house and a high fence blocking Sullivan's view of the barn. And are we to believe he ran 200 feet on a wooden leg, then fought his way through the fire in the barn?

Sullivan also testified that he went to the barn every evening to feed his mother's cow -- also in Mrs. O'Leary's barn. So Sullivan had been in the barn himself. Bayles thinks he started the fire by dropping his pipe -- or maybe by kicking over a lantern.

In any case, Mrs. O'Leary had been home in bed when the fire started. But the fire department ended the hearings quickly -- before it could come out that they'd been taking bribes. They'd been looking after places that could afford bribe money at the expense of Mrs. O'Leary's working-class neighborhood.

As for Mrs. O'Leary: the myth about the kicked lantern grew as the tabloid press went after her. She finally had to flee to Michigan. In those days, it was the Irish who occupied the lowest rung on the social ladder, and Mrs. O'Leary made a good target. But Chicago really burned because all the factors favored a fire -- and no one was paying proper attention.

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

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Belluck, P., Barn door Reopened on Fire After Legend Has Escaped. The New York Times, National Report, Sunday, August 17, 1997, p. 10.

For more on the Chicago fire see Episodes 61 and 836.  For more on the balloon frame house see Episode 779.