by Clark South
angles," the professor reminded him. "Remember, theactual break in the continuum was relatively small. Elaine, seatedbefore the mirror, must have been directly in front of the gap, so shewas sucked through. You, on the other hand--"
"Yes. I was standing up. Off center. So I didn't go." Mark nodded. "Isee."
"And now," said the scientist, "the mirror is broken. Our last chance ofsaving Elaine is gone."
"No!"
"What?" The professor peered up at the other incredulously. "What do youmean, Mark?"
Brown eyes narrowed with excitement, Elaine's sweetheart held out thesplinter of glass he had picked up. He shook it in front of the savant'sface.
"Professor, every piece of glass that went to make up that mirror islaying over there on the floor."
"I am sorry, my boy." The elder man frowned. "I do not understand."
"Professor, if you break your glasses, all you have to do to get a newpair is to take the pieces to an optician. He'll figure the formula ofthe lens from the fragments and make you a new set."
"You mean--"
"I mean that we can put the pieces of that mirror together as if it wasa jigsaw puzzle. From it, you can figure out some kind of a formula.Then, by experimenting, you can find what kind of energy bolt it takesto blast through the barrier!"
* * * * *
Something of the man's intensity, his enthusiasm, communicated itself tothe professor. His blue eyes came alight.
"It is conceivable!" he declared. "Not likely. But conceivable." Hegripped the fragment of glass which Mark held. "Yes! We shall try it! Ifit works, we can--"
He stopped short. His face fell.
"We can what?" he finished. "Another time mirror will not help us bringElaine back--"
His companion interrupted fiercely:
"How do we know? There's always a chance we'll think of something, isn'tthere? And it's a cinch we won't accomplish anything just sitting here."
"But--"
"The least we can do is try!"
They worked like madmen in the hours that followed, heedless of thewedding guests who came and went from the house in bewildered knots.Unmindful of gashed fingers, Mark fitted the slivers of mirror together,while Professor Duchard tested and analyzed and figured at his side.
And then--
"I have it!" shouted the savant triumphantly. "I have the formula!"
"Then we can construct another mirror?"
Some of the old man's elation dropped away. He shook his head.
"Not yet. We know only the _effect_ we want. But how to achieve it--" Heshrugged.
Experiments. More experiments. Hours of experiments, with Mark and theprofessor hovering over an electric crucible bubbling with molten glass.
Hours of failure.
At last the old scientist straightened, his face haggard with weariness.
"It is no use," he said sadly. "I have exhausted my knowledge, and to noavail."
He turned away, shoulders sagging. Stumbled toward the door.
The next instant Mark's voice rose in a scream.
"_Look out!_"
Instinctively, without so much as a backward glance, the old man lungedforward. Even as he did so, he felt something jerk at his ankle. His legcame out from under him. He pitched to the floor.
_Crash!_
The crucible was falling, jerked from its place atop the lab bench! Theelectric cable which supplied its current was twisted about theprofessor's ankle, somehow unconsciously caught by his foot as heworked.
Molten glass burst out of the pot in a white-hot wave. Slopped over thecomposition floor in a steaming river. Engulfed table legs and radiatorpipes alike.
And then, like a writhing snake, the high tension line from which thecrucible cable stemmed was whipping down, torn loose by the jar of theprofessor's leap!
Down it came! Struck the floor once. Lashed against the glass-engulfedradiator pipes, bare wires flashing.
A ball of purple fire exploded at the contact point, while the cablejerked and twisted like a living thing. The laboratory was suddenlypermeated with ozone's peculiar odor.
"Look out!" cried Mark again.
* * * * *
But already Professor Duchard had jerked his foot free of the crucibleline. He shrank back under the long bench, away from the writhing cable.
An instant later the current went dead. The crackling ball of purplefire evaporated into thin air.
Mark sprang across the room to where the scientist lay. He pulled him tohis feet.
"Are you all right, professor? Are you hurt?"
"Yes, yes, my boy. It was a narrow escape, but your warning saved me. Iam all right."
The savant leaned against the bench, trying to still the reflexivetrembling of his body. His face was pale. He ran his tongue over lipssuddenly gone dry as he stared down at the broken high tension line, andthought of what would have happened had it touched him in its spasm.
And then, suddenly, his blue eyes went wide with stark amazement.
"Mark!" he gasped.
"What's wrong, professor? What is it?"
"That glass on the floor! Look at it!"
The other stared uncomprehendingly.
"The waves, Mark! See the waves!"
A startled exclamation burst from the younger man's lips. He dropped tohis knees. Scrutinized the puddle of glass.
But the scientist pulled him erect again.
"My instruments!" he ordered in a voice that trembled. "Quick! I mustmake tests--"
For half an hour he worked. And when at last he straightened, completeconfidence gleamed deep in his eyes.
"Is it--"
Professor Duchard nodded.
"It is. That was the secret, my boy. The secret we sought but could notfind. The time mirror is merely a special glass which has been subjectedto a terrific electrical discharge, then silvered. That piece on thefloor is worthless, of course; too many elements were uncontrolled.
"But knowing the formula as we do; knowing exactly what we are searchingfor and how to prepare it, I would stake my reputation that we canduplicate the mirror Adrian Vance sent to Elaine."
Mark's eyes were gleaming. His jaw hard.
"Then do it!" he commanded.
"But what good would it do? We cannot bring Elaine back--"
"Maybe not." The other's tanned face was grim. "But we can send me backto where she is."
"Send you back!"
"Yes." A pause. "You see, I've been thinking about the things you'vetold me, Professor Duchard. About time travel, and how it works.
"You say we can't save Elaine. Well, that's probably true. Maybe she'sgot to die in France, back in the days before the revolution."
A tremor of emotion passed over him as he said it. He swallowed hard.Then:
"But if she must die, she can at least die easily. Cleanly. Quickly,with a knife through her heart. She doesn't have to go the way AdrianVance wants her to--tortured by a bunch of drunken scum, then cut topieces without a chance to fight back."
* * * * *
There was pain in the professor's face, too, when he answered.
"I wish it were as easy as that, Mark."
Mark's voice was fierce.
"What's wrong with it? What's to stop me?"
The other sighed. Brushed back white hair with a sweep of one frailhand.
"You cannot change history, my boy," he said sadly. "A study ofcosmology would show you that such things are immutable. You can gobackward or forward through time and participate in them, but you cannotchange them."
"How do you know? Who's traveled through time and then come back to saywe can't change events?"
"You do not understand--"
"And I don't care!" the younger man flared. "I may fail--but I'm goingto try! I'm not going to sit here, waiting for Elaine to die--"
"But you would have no memory of your life in this century! Rememberwhat Vance said--"
"Right.
That's the one thing that might stop me. I'm counting on you totake care of it, though. Is there anything you can do?"
There was a long moment of tension-studded silence. Then:
"Perhaps there is. I have been working on equipment to prevent fighterpilots 'blacking out' during power dives, and I believe there is arelationship between time travel and terrific speeds in space. It ispossible that I could insulate you--"
"That's all I need, then. Make me a mirror, professor, and something toinsulate me--"
"But you have no focal point! You might go through time to a place athousand miles and a thousand years from where