In a few hours Marge had grown into a colossus. It was nearly one thousand miles in diameter, with winds exceeding one hundred miles an hour in an area more than two hundred fifty miles in diameter. When the hurricane hunters entered the center and measured the pressure, it proved to be one of the deepest on record—26.45 inches at the lowest point. From plane level, the eye was perfectly clear above, forty miles in diameter and circular. The massive cloud walls around the eye rose on all sides to thirty-five thousand feet, like a giant coliseum. The west wall was almost vertical, with corrugations that suggested the galleries of a gigantic opera house. In the center, below the plane, they saw a mound of clouds rising to about eight thousand feet, an unusual feature, but one that has been observed in other tropical storms. The crew spent fourteen and a half hours in the central region of this huge typhoon, getting data at levels from five hundred feet up to twenty thousand. Down in the lower levels, they found a horizontal vortex roughly five thousand feet in diameter, extending from the cloud wall of the eye like a tornado funnel, in which they encountered very severe turbulence. Another collection of data was added to the growing accumulation and with it the notes of unusual phenomena observed. Since that time Simpson has flown several hurricanes in the Atlantic. Now it is abundantly clear that the hurricane hunters are looking for many important facts aside from the location of the tropical storm and a measure of its violence. There are many questions unanswered. Here in the warm, moist winds that blow endlessly across deep tropical waters there are mysteries that have challenged man for centuries. Turning to their advantage every discovery that science has pointed in their direction, the hurricane hunters have cheated the big storms of the West Indies of a very large share of their toll of human life. In struggling to solve the remainder of the problem, they have two virtues that will ultimately bring success—ingenuity and persistence. They push on tirelessly in several hopeful directions. The Navy has taken advantage of the strange fact that when a tropical storm comes along it literally shakes the earth. There are little tremors like earthquakes but very much smaller. The Greek word for earthquake is _seismos_ and by putting _micro_ in front, meaning very small, we have the word _microseism_. And so, the storm-caused little tremors are called microseisms or slight earthquakes. The instrument which registers these tremors is called a seismograph. When the earth moves, even a very little, a body on the earth tends to hold its position and the earth moves under it. In a small earthquake, a chair will move across the floor. This kind of motion can be registered by instruments.