A little doubtful of his own condition he almost shamefacedly opened the window. The air was cold and fresh and revived him, but it was not the steely, polished, murderous air of the last few days. Somebody passing over the snow below slipped along with a peculiar soaking soddened sound. Fisher craned his head out of the window. Something moist fell on the nape of his neck. He yelled for Gough almost hysterically. Gough also was devoid of his overcoat. "I thought it was fancy," he said unsteadily. Fisher answered nothing. The strain was released, he breathed freely. And outside the whole, white, silent world was dripping, dripping, dripping---- (_Next month Mr. White will tell the story of the "Four Days' Night." He will depict London under the pall of a frightful fog. It is another of the dangers that at any time might come upon London._) [Illustration] THE FOUR DAYS' NIGHT. The Story of a London Fog that turned Daylight into Darkness for Four Days. I. 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.