From men half her age, she always got admiring looks. Ogles, often enough, to call things by their right name.

The thought of young men rallied her. Stop this, woman. He must be fifteen years younger than you are.

Thus fortified, Helen went back to studying A.J. from the perspective of an expert in one field watching another at his own. She did her best to ignore the treacherous little voice at the back of her mind, as it worked its way through simple mathematics.

Don't be silly. He's not as young as he looks. Can't be, not even in his cutting-edge field. He's got to be at least twenty-five or twenty-six. Maybe twenty-seven. Subtracted from thirty-eight, that is not fifteen years younger. It's only eleven. Maybe even less.

Shut up.

"Okay, here we got your GPR unit." A.J. held up a wide metallic antenna unit, followed by a cylindrical object that looked like a solid rod of metal but probably wasn't. "And this here's the impactor for seismic signals, some electromagnetic pulsers-keep metal and electronics that aren't shielded well away, folks-and my own shriekers. High-power ultrasonic pulsers."

The "shriekers" were strange things, looking a bit like large versions of the paddles found on a defibrillator unit, but ending with quivering blobs that looked like nothing so much as firm blue jello. They were labeled Kaled 1 and Kaled 2.

"What's that stuff?" Jackie asked, pointing to the blue blobs.

"Couplant gel. The attenuation of the signal through air is something fierce, so you try to use couplant to bring it more directly to the target. I wash the area off with a high-pressure water jet, then push the gel up against the rock. That increases the efficiency by many times. Even so, it'd be just plain useless without the Fairy Dust. You can immerse a sample in liquid and get good results, but in the field you just wouldn't get the penetration needed. With the sensor motes properly programmed and all over the place, and digitized pulses for signature return filtering, I can get results out of returns almost a hundred times weaker than I could with normal sensors."