" 'Tis but entertainment," the rock assured him.
"An odd word is that. Where hast thou got it?"
"Why," said the rock, " 'twas ever within me, sin that I was made."
"If 'tis witch-moss, one must needs have crafted it." Gwen tilted her head, eyeing the stone. "Who made thee, rock?"
"Another rock," the stone answered.
Gregory looked up at Gwen, startled. "How could another rock have made it?"
"Oh, silly!" Cordelia said in her loftiest manner. "How do mothers and fathers make children?"
Gregory just stared blankly at her, but Fess said, "I doubt it would be quite the same process, Cordelia. After all, the stone referred to only one other rock."
"Then 'tis a babe," Cordelia crowed with delight. "Oh! 'Tis darling! I am half a mind to take thee home with me, as a pet!"
"Do not dream of it," Gwen said instantly. "I've trials enough without music that will not stop in my house."
"It will stop when 'tis indoors." Cordelia turned to the rock. "Thou canst cease making music, canst thou not?"
"Nay," the rock answered. "I am filled with melody; it must come out."
"Art thou never empty, then?" Gregory asked.
"Never," the stone answered firmly. "The music doth but grow and grow inside me, until I feel that I… must… burst!" It bounced out of Cordelia's hand. She gave a wordless cry and grabbed for it, but Magnus caught her wrist. "Let me be!" she snapped, instantly furious. "I must have…" Then her eyes widened, and she stopped, staring, for the rock was rotating on the ground in front of them, hissing over the gauzy, iridescent film that coated the dead leaves under it. Just as suddenly, it stopped.
"How did it know when to turn, and when to stop?" Gregory whispered.
"It has responded to light," Fess pointed out. "Note that it now lies in a sunbeam. It is nearly noon; I believe you will find that it oriented itself by the angle of the sun above the horizon."
Rod stiffened. What Gramarye esper could know about solar cells?
"Would it not rather orient at sunrise or sunset?" Magnus asked.
"No, because at noon, the sun is at its zenith, and its angle above the horizon indicates position north or south. The stone has positioned itself relative to the pole."
"It doth swell," Geoffrey breathed.
They all stared. Sure enough, the stone was growing bigger.
"Back, children!" Gwen ordered, and, "Down!" Rod snapped.
Without demur, they all leaped back and hit the dirt.
"Wherefore, Papa?" Cordelia called.
"Because," Rod answered, "I've known things like rocks that fly apart hard enough to kill people!"
They all wormed back further, Geoffrey, Magnus, and Cordelia hiding behind trees, Gregory ducking behind his parents. Then they peeked out as the rock swelled and swelled, bloating up to twice its original size. It began to tremble and shrink in the middle, pinching in until it looked as though someone had tied a piece of string around it, and kept on shrinking until, with a bang and a metallic crash, it split apart, two pieces flying off into the air.
The children stared, stupefied, but Fess saw a perfectly good demonstration going to waste. "Notice its path as it cuts through the air, children! What is its form?"
"Oh, a parabola," Geoffrey said in disgust.
"We must follow it!" Cordelia leaped to her feet and set off.
"Now, wait a minute," Rod said.
The youth brigade halted in the act of setting forth, then turned back to eye their father with trepidation. "Thou dost intend summat," Magnus accused.
"May I offer an idea for consideration?" Fess asked.
"Which is?" Rod asked.
"Consider: This is presumably the same mechanism that brought the rock here to this location in the first place."
"Certes!" Magnus cried. "That is its meaning, in saying another rock made it!"
"Precisely, Magnus. There was one rock, but there are now two. It has reproduced itself."
"Yet with only one parent!" Cordelia said.
"Indeed. This form of reproducing by splitting is called 'fission.'"
"Yet why did it swell and burst?" Cordelia frowned. "What occasioned it?"
"The sun reaching the zenith no doubt triggered it. As to how it swelled, did you notice where it landed when you dropped it?"
Four pairs of eyes darted to the soft rock, and the gauzy sheen beneath it. The patch of iridescence had shrunk to a half-inch circle around the stone. "It did land in witch-moss," Cordelia breathed, "and did absorb it all."
Rod and Gwen exchanged glances.
"Precisely. Let us hypothesize that it swelled so rapidly because it had only just landed in more witch-moss, and noon was almost upon it."
"Why hypothesize?" Geoffrey demanded. " 'Tis plain and clear!"
"Many things are plain and clear until we count on them, and they fail to happen. If you wish to be sure you have guessed rightly, Geoffrey, you must create the same conditions and see if they cause the same result."
"Why, this is the scientific method of which thou hast taught us!" Magnus cried. "We first observed and gathered information, then we sought to reason out what that information signified, and now we have stated an hypothesis!"
"Thou hast sneaked a lesson upon us, Fess," Cordelia accused.
"Of course; we are still within school hours."
"Keep it up, Metal Mentor," Rod breathed.
"If you insist. I now propose that we test the hypothesis we have formulated."
"Thou dost mean we should experiment," Gregory translated.
Geoffrey glared at him. "Showoff!"
"Wast not thou, with thy catapult?" Gregory retorted.
"Yes!"
"How can we experiment, Fess?" Magnus asked. "Seek another soft rock, and set it in a patch of witch-moss?"
"Yes, and come to look at it shortly before noon tomorrow, to see if it has grown," Fess answered.
"Well enough!" Geoffrey clapped his hands, delighted by the prospect of action. "Let us follow the rock!"
"We could," Rod said thoughtfully, "or we could go in the opposite direction."
Geoffrey halted and turned back, frowning. "Wherefore?"
"Why would a captain do such a thing, son, if he saw a scout ride toward him?"
Geoffrey gazed off into space. "Why—to seek out the army from which the scout rode!"
"And if we do backtrack the rock, we may find its parent?" Cordelia asked, eyes lighting.
"We may indeed," Fess said, "and we can use it for our experiment."
"And in seeking it," Geoffrey asserted, "we will perform another experiment—one that will determine whence the rock came!"
"What a wonderful insight, Geoffrey! Really, there are times when you delight me! You have hit the precise point—that we may as well perform two experiments at once, thus answering two questions for the price of one! Come, children—let us see if we have guessed rightly as to the rock's source!"
Cordelia, Gregory, and Magnus gave a shout and followed Fess away from the musical rock. Geoffrey followed more slowly, flushed with pleasure at Fess's compliment, but somehow feeling he'd been manipulated.
As his parents knew very well he had, and by a master. "I have never truly known Fess's worth as a teacher," Gwen said softly as they followed the children.
"Neither have I," Rod admitted, "and I was his student."
Chapter Three
The Gallowglasses set off cautiously, Fess following behind. They walked awhile in silence. Then Magnus spoke.
"Yet how could a stone make music? 'Tis not in the nature of the substance; rock is hard and unfeeling."
"Tis equally unnatural for stones to be soft, then," Cordelia reminded.
"Not for a stone made of witch-moss," Geoffrey snorted.
"Aye. What is not in the nature of witch-moss?" Gregory asked.