the intensity of the explosion of a hundred tons of high explosive a
very long distance away and barely strong enough to record its
location, which was Boulder Lake. The cause of that explosion or shock
was not observed visually. There'd been no time to alert observers,
and in any case the object should have been out of atmosphere until
the last few seconds of its fall, and where it was reported to fall
the cloud cover was unbroken. So nobody reported seeing it. Not at
once, anyhow, and then only one man.

Lockley did not feel the impact. He was drinking a cup of coffee and
thinking about his own problems. But a delicately balanced rock a
hundred yards below his camp site toppled over and slid downhill. It
started a miniature avalanche of stones and rocks. The loose stuff did
not travel far, but the original balanced rock bounced and rolled for
some distance before it came to rest.

Echoes rolled between the hillsides, but they were not very loud and
they soon ended. Lockley guessed automatically at half a dozen
possible causes for the small rock-slide, but he did not think at all
of an unperceived temblor from a shock like high explosives going off
thirty miles away.

Eight minutes later he heard a deep-toned roaring noise to the
northeast. It was unbelievably low-pitched. It rolled and reverberated
beyond the horizon. The detonation of a hundred tons of high
explosives or an equivalent impact can be heard for thirty miles, but
at that distance it doesn't sound much like an explosion.

He finished his breakfast without enjoyment. By that time well over
three-quarters of the Air Force on the Pacific Coast was airborne and