Jack set the men to work digging holes,—like post holes in the ice at regular intervals right across the valley. When this had been done an oar was set up at each end of the row of holes.
“Now we’ll load ’em,� said Jack, and into each hole a “capped� charge of explosive was placed, being tamped down carefully.
When this had been done the copper wire was stretched from one oar to the other like a telegraph wire. From this main wire branch, wires were led to each of the loaded holes and there carefully attached to the fulminate of mercury caps. When all this had been done to Jack’s satisfaction, he electrified the system with his batteries, attaching them to the main wire.
“Now we’ll pull back to the ship,� he said.
“Beg pardon, sir, but ain’t you going to touch off all that dynamite?� asked the coxswain.
“And blow ourselves up as well as the berg? Not much,� laughed Jack, “come on, boys, give way lively now, and before long you’ll see fireworks.�
In a short time they were back on the ship. Jack reported to Captain Simms that everything was in readiness for the long distance explosion. All eyes turned curiously on the lad as he walked aft to the wireless room, for word had spread through the ship of the experiment that was to be tried.
Jack tested up his instruments carefully. Then he adjusted the dynamo for an extra heavy current of “juice.� When this had been done, he sat down coolly at the key.
“Now watch the berg!� he shouted, and the cry was taken up and passed along the decks.
He pressed down the key. There was a snap and a crackle as the live flame leaped between its points. Far above from the aërials, an invisible wave of electricity rolled.