Seeing Koku near the instrument, Eradicate had switched on the amplifier, and had called into his instrument, trying to scare the giant.  And he did startle Koku, for the loud voice, coming so suddenly, sent the giant out of the booth on the run.

“But you must have done something else,” insisted Tom.  “Look here, Rad,” and the young inventor pointed to the picture on the plate.

“Mah gracious sakes!” gasped the colored man.  “Why dat’s Koku hisse’f!” and he looked in awe at the likeness.

“That’s what you did, Rad!”

“Me?  I done dat?  No, sah, Massa Tom.  I neber did!  No, sah!” Eradicate spoke emphatically.

“Yes you did, Rad.  You took that picture of Koku over my photo telephone, and I want you to show me exactly what you did—­what wires and switches you touched and changed, and all that.”

“Yo—­yo’ done say I tuck dat pishure, Massa Tom?”

“You sure did, Rad.”

“Well—­well, good land o’ massy!  An’ I done dat!”

Eradicate stared in wonder at the image of the giant on the plate, and shook his head doubtingly.

“I—­I didn’t know I could do it.  I never knowed I had it in me!” he murmured.

Tom and Ned laughed long and loud, and then the young inventor said: 

“Now look here, Rad.  You’ve done me a mighty big service, though you didn’t know it, and I want to thank you.  I’m sorry about your arm, and I’ll have the doctor look at it.  But now I want you to show me all the things you touched when you played that joke on Koku.  In some way you did what I haven’t been able to do, You took the picture.  There’s probably just one little thing I’ve overlooked, and you stumbled on it by accident.  Now go ahead and show me.”

Eradicate thought for a moment, and then said: 

“Well, I done turned on de current, laik I seen you done, Massa Tom.”

“Yes, go on.  You connected the telephone.”

“Yas, sah.  Den I switched on that flyer thing yo’ all has rigged up.”

“You switched on the amplifier, yes.  Go on.”

“An’—­an’ den I plugged in dish year wire,” and the colored man pointed to one near the top of the booth.

“You switched on that wire, Rad!  Why, great Scott, man!  That’s connected to the arc light circuit—­it carries over a thousand volts.  And you switched that into the telephone circuit?”

“Dat’s what I done did, Massa Tom; yas, Bah!”

“What for?”

“Why, I done want t’ make mah voice good an’ loud t’ skeer dat rascal Koku!”

Tom stared at the colored man in amazement.

“No wonder you got a shock!” exclaimed the young inventor.  “You didn’t get all the thousand volts, for part of it was shunted off; but you got a good charge, all right.  So that’s what did the business; eh?  It was the combination of the two electrical circuits that sent the photograph over the wire.”

“I understand it now, Rad; but you did more than I’ve been able to do.  I never, in a hundred years, would have thought of switching on that current.  It never occurred to me.  But you, doing it by accident, brought out the truth.  It’s often that way in discoveries.  And Koku was standing in the other telephone booth, near the plate there, when you switched in this current, Rad?”