A print upon “positive” film was made from each:  every strip was duplicated twenty-five times, at Shirley’s suggestion.  Then after two hours of effort the material was ready to be run through the projecting machine, for viewing upon the screen.

The manager led Shirley to the small exhibition theatre in which every film was studied, changed and cut from twenty to fifty times before being released for the theatres.  The camera man went into the little fire-proof booth, to operate the machine.

“Which one first, chief?”

“Take one by chance,” said Shirley, “and I will guess its number.  Start away.”

There was a flare of light upon the screen, as the operator fussed with the lamp for better lumination.  He slowly began to turn the crank, and the criminologist watched the screen with no little excitement.  The picture thrown up resembled nothing so much as three endless snakes twisting in the same general rhythm from top to bottom of the frame.  The twenty-five duplicates were all joined to the original, so that there was ample opportunity to compare the movements.

“Well, gov’nor, which film was that?” asked the operator.

“Not A—­it was B or C!”

“Correct.  How’d you guess it?  Which is this one?”

As he adjusted another roll of film in the projector, Shirley turned to the manager sitting at his side.  “Mr. Harrison, were those snakes all exactly alike?”

“No.  They all wriggled in the same direction, at the same time.  But little rough angles in some movements and queer curves in others made each individually different.”

“Just what I thought.  There goes another.—­That is not film A, either!”

“Righto!” confirmed the camera man.  As the detailed divergence between the lines became more evident in the repetitions, Shirley slapped his knee.

“Now for the finish.  Try reel A.”

This time the three snakey lines moved along in almost identical synchronism.  The only difference was that the first was thin, the second heavier, the third the darkest and most ragged of all.  The relationship was unmistakable!

“I got you gov’nor,” cried the operator.  “Some dope, all right, all right.”

“Why, what is all this?” asked the manager, nonplussed.  “The last three are alike, but what good does it do?”

“It is known that the human voice in its inflections is like handwriting—­with a distinct personality.  Certain words, when pronounced naturally, without the alterations of dialect, are always in the same rhythm.  The records taken in the studio of those five words, ‘Can you hear me now?’ are in the same general rhythm, but only the last three snakes show exact similarity, to each little quaver and turn.  There was only the difference in shading:  one was the voice of a women.  The second of a man of perhaps forty, the third of an old man—­all three taken at different times, and I thought from different people.  But they all came from one throat, and my work is completed along this line—­Will you please lock up the films, the phonograph, and my records in your film vault, until I send for them; through Mr. Holloway?”