CHAPTER XIV AN IMPORTANT DISCOVERY
That night as he tramped the deck on his silent watch, Johnny found hismind crowded with disturbing thoughts of the significant message thegreen arrow had flashed over the sea.
"_We will strike_--" his mind went over the words again and again, "_atthe earliest possible moment!_" Where would they strike? And who was toreceive the blow? His shipmates on the _Sea Nymph_? Old Kennedy and hisdaughter? Or someone he never had seen?
"I may never know," he told himself. "Spies strike in the dark."
Johnny had read that during the World War, spies had swum to thepropellers of outgoing ships laden with men and supplies. Hours later,with the ship far out at sea, a bomb had exploded, blowing away thepropeller and leaving the ship helpless. He knew, too, that spies hadplaced incendiary bombs in the holds of ships, and dumped quantities ofacid in the very bottom of a vessel, to eat its way through the steel.
"Yes," he thought, "and even now--in times of supposed peace--they areboring in!"
* * * * * * * *
The _Sea Nymph_ left the river and put out to sea while Johnny slept.When he awoke in mid-afternoon, they were anchored in their old position.
"How would you like to make a solo journey in the steel ball?" Dave askedwhen he came on deck.
"Go--go down alone?" Johnny asked, feeling a bit strange. "That--oh,that's O.K., I guess."
"I was down this morning," said Dave, "and my eyes are tired. There aresome pictures I'd like to have. Conditions below are all right, andthere's an off-shore breeze. We've two lines out to windward, whichshould hold her steady.
"What the professor would like," he went on in a businesslike tone, "isto have you go down, slowly, along that submerged cliff, stopping everyten feet to take a photo floodlight picture. That will give us acontinued story of plant and animal life, down to perhaps two thousandfeet."
"Al--all right," Johnny agreed. "I can do that." But for the life of himhe could not still his heart's wild beating. He seemed to be hearing avoice say:
"_We will strike--at the earliest possible moment!_"
He forced his lips to repeat: "Two thousand feet, you say?"
"About that. Better get ready at once. The wind may pick up."
"Yes, it may stri--pick up," Johnny agreed a little absently.
Twenty minutes later, inside the steel ball and busy taking pictures ofthe wall as he stopped each ten feet, he had all but banished thoughts ofthe green arrow from his mind.
* * * * * * * *
But someone else really was seeing green arrows--and plenty of them. Thatwas the granddaughter of old Mr. Kennedy--the man who for twenty yearshad defied encroachments of foreign interests in this happy littlerepublic. For Mildred had gone on a hunting expedition all her own. Shewas hunting spies. She had started once more over the green arrow trailand, strangely enough, almost instantly had discovered the secret of itsmarkings.
During their months together she and her grandfather had spent hours onend, tramping the jungle, and he had taught her to know all the usualsigns. The trail of some great snake in the sand--the uprooted earth,where little wild pigs had been--the marks of a monkey's claws on thegreen sprouts of a tree--all had a meaning for her.
Knowing these usual signs, she had looked for unusual ones--and had foundthem. On reaching the spot where they had lost the trail on two otheroccasions, she noted that the next to the last arrow was low down, whilethe _last_, was some ten feet higher. So--to reach this last markingplace--someone had been obliged to climb! In doing this, bits of bark hadbeen broken off, leaving fresh, light-brown spots on the tree trunks.
"Now I shall look for broken bark--not arrows," she told herself.
She had not gone forward a hundred paces on the right hand fork of thetrail, when she let out a cry of surprise and joy. Not only had shediscovered broken bark, but up, perhaps thirty feet on a tree, she saw agreen arrow.
"One, two, three," she whispered. "Perhaps that's the way it goes. Onearrow down low, one a little higher, and a third, well up on the trunk!"
She discovered at once that this was just the way the markings ran. Soimmediately she took up the trail again.
The distance from the shore of the island to the summit of the tallesthill, was considerable. The trail, such as it was, made only by nativesand wild animals, wound round and round--up and up.
The girl followed this trail for more than an hour. Then she sat down ona fallen mahogany tree to think. She was far from all her friends. Shouldshe go farther? She, too, recalled the last message of the green arrow oflight--about "striking"!
"Perhaps I can stop them," she whispered stoutly, as she rose to herfeet. "At least I can try!"
Though her knees trembled, she did not falter, but marched straight on.For was she not the granddaughter of old Kennedy--hero of a hundredbattles?