But what really interested the Chief that morning was a bulge eastward of the 1011 isobar, looping around Salt Lake City. It was not a prominent feature of the map, but to the Chief it was the indication that things were getting back to normal, that the ordinary movement of air from west to east was being re-established. It meant that some of the air from the Pacific storm had got across the mountains, and was about to form a secondary storm-center over Nevada or Utah. From there it would go east. Already air was moving up from the Gulf and warming Texas and Oklahoma.

In this plains region and farther east had come the greatest weather-shift of the last twenty-four hours. Over most of the Mississippi Valley the north wind had ceased blowing, and had left the weather cold, clear, and still. The center of the High forming the calm area had drifted slowly eastward from Kansas City to Terre Haute. Peoria reported eleven below zero. Farther east the temperatures were not so low, but the air was still pouring down from the Arctic. Crossing the Lakes this air picked up some moisture, enough to let loose snow flurries upon Buffalo, Cleveland and Detroit, and even as far south as Pittsburgh.

As the Chief decided finally, the restoration of more normal conditions would not proceed very rapidly. The storm off the coast still looked good for forty-eight hours of rain in California. But the bulging out eastward had already caused a breaking of the cold wave on the plains.

Then he checked himself, and shrugged his shoulders. “Hn-n?” He had merely yielded to that incurable human tendency to see things from your own point of view. Weather-men in the plains states would be saying that the flow of air from the south across the plains had caused the storm to bulge out eastward. Did one side of the scale go down because it was heavier, or did the other side go up because it was lighter? It all depended upon how you looked at the matter. The whole atmosphere was in exact balance; this particular problem had no solution. The more you thought about which caused what, the more you felt cause and effect to be nothing except words—convenient to use at times, but not really meaning much. The Chief wondered whether he would know more about it if he had taken courses in philosophy.

•

The same problem was involved in what was happening concurrently in South America, where an intensely heated tropical air-mass had moved down from the Amazon Valley. Superficially, one might have said that the great incursion of polar air, reaching clear to Panama, had disturbed the equilibrium and pushed the equatorial air southward. Equally well, one could say that the movement of the equatorial air had permitted the unusual southern push of the polar air. Both statements would have ignored the existence of an intensified circumpolar whirl over Antarctica, a willy-willy in Western Australia, and the weather elsewhere in the world.