The weather forecast for London and the Channel was "light airs, fine generally, milder." Further down the fascinating column Hackness read that "the conditions over Europe generally favoured a continuance of the large anti-cyclonic area, the barometer steadily rising over Western Europe, sea smooth, readings being unusually high for this time of the year."

Martin Hackness, B.Sc., London, thoughtfully read all this and more. The study of the meteorological reports was part of his religion almost. In the laboratory at the back of his sitting-room were all kinds of weird-looking instruments for measuring sunshine and wind pressure, the weight of atmosphere and the like. Hackness trusted before long to be able to foretell a London fog with absolute accuracy, which, when you come to think of it, would be an exceedingly useful matter. In his queer way Hackness described himself as a fog specialist. He hoped some day to prove himself a fog-disperser, which is another word for a great public benefactor.

The chance he was waiting for seemed to have come at last. November had set in, mild and dull and heavy. Already there had been one or two of the dense fogs under which London periodically groans and does nothing to avert. Hackness was clear-sighted enough to see a danger here that might some day prove a hideous national disaster. So far as he could ascertain from his observations and readings, London was in for another dense fog within the next four-and-twenty hours. Unless he was greatly mistaken, the next fog was going to be a particularly thick one. He could see the yellow mists gathering in Gower Street, as he sat at his breakfast.

The door flew open and a man rushed in without even an apology. He was a little man, with sharp, clean-shaven features, an interrogative nose and assertive pince-nez. He was not unlike Hackness, minus his calm ruminative manner. He fluttered a paper in his hand like a banner.

"It\'s come, Hackness," he cried. "It was bound to come sometime. It\'s all here in a late edition of the Telegraph. We must go and see it."

He flung himself into an armchair.

"Do you remember," he said, "the day in the winter of 1898, the day that petroleum ship exploded? You and I were playing golf together on the Westgate links."

Hackness nodded eagerly.

"I shall never forget it, Eldred," he said, "though I have forgotten the name of the ship. She was a big iron boat, and she caught fire about daybreak. Of her captain and her crew not one fragment was ever found."

"It was perfectly still and the effect of that immense volume of dense black smoke was marvellous. Do you recollect the scene at sunset? It was like looking at half-a-dozen Alpine ranges piled one on the top of the other. The spectacle was not only grand, it was appalling, awful. Do you happen to recollect what you said at the time?"

There was something in Eldred\'s manner that roused Hackness.

"Perfectly well," he cried. "I pictured that awful canopy of sooty, fatty matter suddenly shut down over a great city by a fog. A fog would have beaten it down and spread it. We tried to imagine what might happen if that ship had been in the Thames, say at Greenwich."

"Didn\'t you prophesy a big fog for to-day?"

"Certainly I did. And a recent examination of my instruments merely confirms my opinion. Why do you ask?"

"Because early this morning a fire broke out in the great petroleum storage tanks, down the river. Millions of gallons of oil are bound to burn themselves out—nothing short of a miracle can quench the fire, which will probably rage all through to-day and to-morrow. The fire-brigades are absolutely powerless—in the first place the heat is too awful to allow them to approach; in the second, wate............