Southern Californians were awakened earlier this year by an earthquake. Last fall Midwesterners had to cope with floods. Can you imagine, though, sleeping through a tornado? Bill Bryson says his grandparents pretty much did.

One night they were suddenly awakened by a roaring noise like the sound of a thousand chain saws. For a few moments the whole house shook. Pictures fell off the walls. A clock fell off the mantle in the living room. Bill's grandfather got up, plodded over to the window and peered out. But he couldn't see a thing, just pitch blackness, so he climbed back into bed, remarking that it seemed a bit stormy out there. He didn't realize that, at the very moment he was looking out the window, a tornado was thundering across their lawn. It was so close that if he had opened the…