THE SHADE OF J. BALLANTINE HANNAY 241
and
loses its charge, becoming negative, so it is pulled toward the upper
electrode, which is positive. The attraction carries it past the area
of the field, and it falls into the reject bin. But the diamonds, not
being good conductors, don't lose their charge so quickly to the
earthed electrode. They are still positive, and so they are not
attracted by the positive electrode, but are repelled before they pass
out of the field. Instead they fall short of that upper electrode, into
another bin, and there you are."
Now
he paused and waited for me to catch up. I said, "But that only works
if you have non-conductive diamonds, didn't you say so?" He nodded.
"And so-----" I began.
He
cut in and finished for me. "And so," he said, smiling, "you lose your
2-B diamonds. That is true, but we've only just found it out."
In
London some weeks later, I went to the Museum of Natural History to
look at the Hannay diamonds and see for myself whatever could be seen.
Like that man in Mr. White's office, I couldn't stop thinking about
Hannay and the excitement he caused back in 1880, compared with General
Electric and the discoveries of 1955. I didn't know just what to
expect: I had got the idea from what Mr. White said that the diamonds
would be out on public display under glass, perhaps with Hannay's
apparatus laid out next to them. But they weren't on public display. I
wandered along a hall thronged with glass cases of plaster models of
dinosaurs, and genuine dinosaur skeletons mounted in awesome procession
down the middle of the passage, until I came to a wooden wall and a
locked door and a sign saying that here was the Mineral De-
