"Now, the air, as you know, is held to the earth's surface by gravitation, but, being gaseous, it is not held as closely as if it were in a solid state. Also, there is centrifugal force to be considered. Also the fact that the earth is not round, but flattened at the poles. Also the important fact that air at the equator is more heated than at the Polar regions. All these things together keep the air in a constant commotion. The combined effect of these, in the northern hemisphere, is that air moving along the surface of the earth is deflected to the right. Thus in the case we are considering, the lower currents, approaching the heated center, do not come in equally from all directions, but are compelled to approach in spirals. This spiral action once begun increases, of itself, in power and velocity. This is a hurricane in its baby stage." Another squall struck. Speech again became impossible. As before, sheets of water--which bore no relation to rain, but seemed rather as though the earth were at the foot of a waterfall from which a river was leaping from on high--were hurled over the land. The shrieking of the wind had a wild and maniacal sound, the sound which Jamaicans have christened "the hell-cackle of a hurricane." This squall lasted longer, five minutes or more, and when it passed, the wind dropped somewhat, but did not die down. It raged furiously, its shriek dropped to a sullen and menacing roar. "Such a hurricane as this," the "Ol' Doc" continued, "has taken many days to brew. Day after day the air has remained in its ominous quietude over the surface of the ocean, becoming warmer and warmer, gathering strength for its devastating career. The water vapor has risen higher and higher. Dense cumulus clouds have formed, the upper surfaces of which have caught all the sun's heat, intensifying the unstable equilibrium of the air. The powers of the tempest have grown steadily in all evil majesty of destructiveness. Day by day, then hour by hour, then minute by minute, the awful force has been generated, as steam is generated by fierce furnace fires under a ship's boilers. "Why, Stuart, it has been figured that the air in a hurricane a hundred miles in diameter and a mile high, weighs as much as half-a-million Atlantic liners, and this incredibly huge mass is driven at twice the speed of the fastest ship afloat. In these gusts, which come with the rain squalls, the wind will rise to a velocity of a hundred and twenty miles an hour. It strikes!" A crack of thunder deafened all, and green and violet lightning winked and flickered continuously. The hiss of the rain, the shrieking of the wind and the snapping crackle of the thunder defied speech. The heat in the hurricane wing was terrific, but Stuart shivered with cold. It was the cold of terror, the cold of helplessness, the cold of being powerless in such an awful evidence of the occasional malignity of Nature.