"Darrow got his idea from watching a rapidly revolving wheel. He noticed that the spokes and rim blended into a blurred disc when a certain speed was reached. The entire wheel was practically invisible, under certain lighting conditions, when a higher speed was attained.
"Darrow went further and reached the conclusion that there was a rate of vibration that would produce invisibility. This was accepted in practically all engineering research plants, long before it was perfected by Darrow.
"The facts are that any rapidly vibrating object becomes more and more difficult to outline as its rate of vibration increases. All that was left for Darrow was to arrive at the exact mathematical time, tone, or rate of vibration producing invisibility and to construct a vibrator tuned to produce this condition.
"His first machine produced the vibrations of invisibility in a field with a three-foot radius in all directions. That is, it caused every solid object, within this atmospheric field, to vibrate at the rate, tone, or speed of invisibility. This machine was in no sense rotary. It departed from the original example of a revolving wheel and entered instead into general vibration in a given or measured field.
"The pulsations or vibrations of an ordinary automobile engine will cause every ounce of metal, or solid, in the automobile—including the driver—to vibrate at the same rate or momentum. This is a known fact, and it provided the basis for Darrow's experiments.
"Darrow built two machines. The first had a field with a radius of three feet on all sides. This was used by the killer in his murders. Jouret stole this machine first, thus paving his way for the second robbery.
"With the first machine in his possession, Jouret was able to commit the Darrow murder without being seen. He had to have the second and larger machine, however, to make his auto disappear. He stole the larger machine at the time of the Darrow murder, and with it he had his auto vanish, as the gardener testified.
"Both machines were hopelessly smashed in the wreck, but with Darrow's documents at hand, we might be able to construct another and a larger model. A machine built on the proper scale will make a plane or a battleship invisible and should, as Darrow said, make war against this country impossible.