There was no way of telling exactly how high it was but if it were at 6,000 feet, as the major estimated, it would have been about 125 feet in diameter. They checked aircraft flights, rephotographed the area from high and low altitude to see if they could pick up something on the ground that could have been reflecting light, and made a minute ground search of the area.
"I overcome the difficulty by having lenses of sufficient rapidity to photograph even faint images on that screen. It is better than the so-called serial method, by which a number of separate X-ray pictures are taken and then pieced together and rephotographed to make the film. I can focus the X-rays first on the screen by means of a special quartz objective which I have devised.