The Deadly Dust by Murray Leinster - When Geiger counters all over America went into too–high gear, Dr. David Murfree knew that there was only one man to see–Bug Gregory, the hillbilly genius of the atom!

A sturdy, small fishing-boat wallowed and rolled and heaved and pitched in the huge slow swells of mid-Pacific. It looked very much like any other fishing-boat and remarkably like those tuna-boats that put out from the West Coast of the United States and pursue their prey for as many thousands of miles as may be necessary.

It was just a little over a hundred feet long and was powered obviously by a Diesel engine. There was just one thing odd about the boat and one oddity about its crew and one about the object it towed and one about its wake.

The odd thing about the boat was that something remarkably like a radar antenna was fitted atop its pilot-house. The oddity about its crew was that every man wore heavy protective clothing of a sort usually found only among workers about atomic piles.

The oddity about the object it towed was that aside from the supporting pontoons that kept it afloat it was made of lead. It was a torpedo-shaped object some forty feet long and no more than eight or ten feet in diameter, kept from sinking by sheet-metal floats on either side.

The oddity of the wake was that it was quite clear for a few miles and then—miles and miles behind—dead fish lay on the water. It was possible to back-track the tuna-boat for a long, long way by dead fish lying on the surface. Of course, perhaps fifty miles astern the dead fish had been scattered by the waves and the trail had been thinned out and was not so clear.

But the fishy corpses made a trail for a hundred miles beyond that if you looked for them.