In this reply Robin's mind was running on previous conversations which he had had with his friend on predestination.

The idea of shrubs and trees having been expressly grown on an island of the Southern Seas to save an English boy, seemed doubtful to Sam. He did not, however, express his doubts at the time, but reserved the subject for a future "theological discussion."

Meanwhile, Slagg, Stumps, and Johnson, having spread some palm branches on a couple of stout poles, laid our hero thereon, and bore him in safety to the pirates' cave, where, for several days, he lay on one of the luxurious couches, tenderly nursed by Letta and the old woman, who, although she still pathetically maintained that the "roberts an pyrits wasn't all so bad as each oder," was quite willing to admit that her present visitors were preferable, and that, upon the whole, she was rather fond of them.

CHAPTER TWENTY.

VARIOUS SUBJECTS TREATED OF, AND A GREAT FIGHT DETAILED.

It was the habit of Robin and his friends at this time, the weather being extremely fine and cool, to sit at the mouth of their cavern of an evening, chatting about the events of the day, or the prospects of the future, or the experiences of the past, while old Meerta busied herself preparing supper over a fire kindled on the ground.

No subject was avoided on these occasions, because the friends were harmoniously minded, in addition to which the sweet influences of mingled star-light and fire-light, soft air, and lovely prospect of land and sea--to say nothing of the prospect of supper--all tended to induce a peaceful and forbearing spirit.

"Well, now," said Robin, continuing a subject which often engaged their intellectual powers, "it seems to me simple enough."

"Simple!" exclaimed Johnson, with a half-sarcastic laugh, "w'y, now, you an' the doctor 'ave tried to worrit that electricity into my brain for many months, off an' on, and I do believe as I'm more muddled about it to-night than I was at the beginnin'."

"P'r'aps it's because you hain't got no brains to work upon," suggested Slagg.

"P'r'aps it is," humbly admitted the seaman. "But look here, now, doctor," he added, turning to Sam with his brow knotted up into an agony of mental endeavour, and the forefinger of one hand thrust into the palm of the other,--"look here. You tells me that electricity ain't a substance at all."

"Yes, that's so," a.s.sented Sam with a nod.

"Wery good. Now, then, if it ain't a substance at all, it's nothin'.

An' if it's nothin', how can you go an' talk of it as somethin' an' give it a name, an' tell me it works the telegraph, an' does all manner of wonderful things?"

"But it does not follow that a thing must be nothing because it isn't a substance. Don't you see, man, that an idea is something, yet it is not a substance. Thought, which is so potent a factor in this world, is not a substance, yet it cannot be called nothing. It is a condition--it is the result of brain-atoms in action. Electricity is sometimes described as an `invisible imponderable fluid,' but that is not quite correct, because a fluid is a substance. It is a better definition to say that electricity is a _manifestation of energy--a result of substance in action_."

"There, I'm muddled again!" said Johnson, with a look of hopeless incapacity.

"Small blame to you, Johnson," murmured Slagg who had done his best to understand, while Stumps sat gazing at the speakers with an expression of blank complacency.

"Look here, Johnson," said Sam, "you've often seen men shaking a carpet, haven't you?"

"In coorse I have."

"Well, have you not observed the waves of the carpet that roll along it when shaken!"

"Yes, I have."

"What are these waves?"

"Well, sir, I should say they was the carpet," replied Johnson.

"No, the waves are not the carpet. When the waves reach the end of the carpet they disappear. If the waves were the carpet, the carpet would disappear. The same waves in a whip, soft and undulating though they be, result in a loud crack, as you know."

"Muddled again," said Johnson.

"Ditto," said Slagg.

"Why, I'm not muddled a bit!" suddenly exclaimed Stumps, with a half-contemptuous laugh.

"Of coorse you're not," retorted Slagg. "Brainless things never git into that state. You never heard of a turnip bein' muddled, did you?"

Stumps became vacant, and Sam went on.

"Well, you see, the waves are not substance. They are a condition--a result of atoms in motion. Now, when the atoms of a substance are disturbed by friction, or by chemical action, they get into a state of violent commotion, and try wildly to fly from, or to, each other. This effort to fly about is energy. When the atoms get into a very intense state of commotion they have a tendency to induce explosion, unless a way of escape is found--escape for the energy, not for the atoms. Now, when you cause chemical disturbance in an electric battery, the energy thus evolved is called electricity, and we provide a conductor of escape for it in the shape of a copper or other metal wire, which we may carry to any distance we please, and the energy runs along it, as the wave runs along the carpet, as long as you keep up the commotion in the battery among the excited atoms of copper and zinc."

"Mud--no, not quite. I have got a glimmer o' su'thin'," said Johnson.

"Ditto," said Slagg.

"Supper," said old Meerta.

"Ha! that's the battery for me," cried Stumps, jumping up.

"Not a bad one either," said Robin, as they entered the cave; "alternate plates of beef and greens, steeped in some such acid as lemonade, cause a wonderful commotion in the atoms of the human body."

"True, Robin, and the energy thereby evolved," said Sam, "sometimes bursts forth in brilliant sparks of wit--to say nothing of flashes of absurdity."

"An' thunderin' stoopidity," added Slagg.

Further converse on the subject was checked at that time by what Sam termed the charging of the human batteries. The evening meal went on in silence and very pleasantly for some time, but before its close it was interrupted in an alarming manner by the sudden entrance of Letta with wild excitement in her eyes.

"Oh!" she cried, pointing back to the entrance of the cave, "a ship!-- pirate-ship coming!"

A bombsh.e.l.l could scarcely have produced greater effect. Each individual leaped up and darted out, flushing deep red or turning pale, according to temperament. They were not long in verifying the statement. A ledge of rocks concealed the entrance to the cavern from the sea. Over its edge could be seen the harbour in which they had found the vessel whose total destruction has been described; and there, sure enough, they beheld a similar vessel, though considerably smaller, in the act of furling her sails and dropping anchor. There could be no doubt as to her character, for although too distant to admit of her crew being distinguished by star-light, her rig and general appearance betrayed her.

"Not a moment to be lost, Robin," said Sam Shipton hurriedly, as he led the way back to the tavern, where old Meerta and blind Bungo, aided by Letta, had already cleared away all evidence of the late feast, leaving only three tin cups and three pewter plates on the table, with viands appropriate thereto.

"Ha! you're a knowing old lady," exclaimed Sam, "you understand how to help us, I see."

"Me tink so!" replied Meerta, with an intelligent nod. "On'y us t'ree here. All de pyrits gone away. Dem sinners on'y come here for a feed-- p'r'aps for leetil poodre. Soon go away."

"Just so," said Sam, "meanwhile we will hide, and return after they are gone, or, better still, if you, Letta, and Bungo will come and hide with us, I'll engage to lay a train of powder from the barrels inside to somewhere outside, and blow the reptiles and the whole mountain into the sea! There's powder enough to do it."

"You tink me one divl?" demanded the old woman indignantly. "No, some o' dem pyrits not so bad as each oder. You let 'em alone; me let you alone."

This gentle intimation that Meerta had their lives in her hand, induced Sam to ask modestly what she would have him do.

"Go," she replied promptly, "take rifles, swords, an' poodre. Hide till pyrits go 'way. If de finds you--fight. Better fight dan be skin alive!"

"Unquestionably," said Sam, with a mingled laugh and shudder, in which his companions joined--as regards the shudder at least, if not the laugh.

Acting promptly on the suggestion, Sam armed himself and his comrades each with a good breech-loading rifle, as much ammunition as he could conveniently carry, and an English sword. Then, descending the mountain on the side opposite to the harbour they disappeared in the dark and tangled underwood of the palm-grove. Letta went a short distance with them.