“Spinning the windshield—or even part of it—obviously wasn’t practical. Vibrations had to be the answer; but what kind?

“First I tried to drive the whole windshield like a loudspeaker cone. That certainly kept the rain off, but then there was the noise problem. So I went ultrasonic; it took kilowatts of power—and all the dogs in the neighborhood went crazy. Worse still, few windshields lasted more than a couple of hours before they turned into powdered glass.

“So I tried subsonics. They worked better—but gave you a bad headache after a few minutes of driving. Even if you couldn’t hear them, you could feel them.

“I was stuck for months, and almost gave up the whole idea, when I realized my mistake. I was trying to vibrate the whole massive sheet of multiplex safety glass—sometimes as much as ten kilograms of it. All I needed to keep dancing was a thin layer on the outside; even if it was only a few microns thick, it would keep the rainwater off.

“So I read all I could about surface waves, transducers, impedance matching—”

“Whoa! Can we have that in words of one syllable?”

“Frankly, no. All I can say is that I found a way of confining low-energy vibrations to a very thin surface layer, leaving the main bulk of the windshield unaffected. If you want details, I refer you to the basic patents.”

“Happy to take your word for it, Mr. Emerson. Now, our next guest—”

Possibly because the interview had taken place in London, where the works of the New England transcendentalist were not everyday reading, Emerson’s host had failed to make the connection with his famous namesake (no relation, as far as he knew). No American interviewer, of course, missed the opportunity of complimenting Roy on inventing the apocryphal Better Mousetrap. The automobile industry had indeed beaten a path to his door; within a few years, almost all the world’s millions of metronoming blades had been replaced by the Sonic Wave Windshield Wiper. Even more important, thousands of accidents had been averted, with the improvement of visibility in bad-weather driving.