Danny’s face was glowing with the excitement he felt when he was involved in a new project, and he carried his friends along with him so that they generally forgot everything else. “You’ve got an old pair of field glasses, Irene. They have prisms in them. Go get ’em. I’ll be able to take them apart easily and put them together again—I did it with a pair of my mother’s bird-watching glasses once.”
Irene scampered off.
Joe said, “What else do you need? A periscope sounds like a complicated kind of thing. Do you need a submarine to go with it?”
“No, it’s simple. Just two prisms mounted at each end of a long tube. I think I can use some old copper pipe we have in the garage.” Danny frowned, pensively. “It’ll have to be pretty long, though. We’ll have to measure the distance from the window to the ground.”
“Now, listen,” Joe protested. “If you think I’m going to climb up the side of your house with a ruler—”
“No, there’s an easier way. And it’s very interesting, too. I’ll show you.”
Danny took out his pocketknife and after searching about found a straight, thin sapling. He cut it off near the ground and trimmed the twigs from it.
“My hand span, from the tip of the thumb to the tip of the little finger when my fingers are stretched out, is exactly six inches,” he said. “I measured it once so I’d never need to carry a ruler with me. So now I’ll make this stick four spans long—just two feet.”
He cut it off and led Joe out of the shadows of the trees onto the lawn. He stood the stick on end and asked Joe to hold it upright. Then he knelt down and in the same way measured its shadow.
“Aha!” he cried. “A two-foot stick throws a three-foot shadow.”
“Fine. Congratulations,” said Joe. “I’m sure this is a great discovery, but I don’t get it.”
“Now we measure the shadow of the house,” said Danny. He ran to the corner of the house and, on his knees, began spanning the edge of the long shadow cast across the grass.
Irene ducked through the lilacs with the field glasses in her hand. She gaped at Dan and said, “What on earth are you looking for?”
“Sh!” said Joe. “Don’t interrupt him. He’s measuring shadows.”
Irene stared at him, and he stared back. Then he raised his eyebrows and shrugged. “You’re right,” he said. “It does sound kind of nutty, doesn’t it?”
“Thirty feet,” Danny said triumphantly, standing erect.
“Listen, Dan,” said Irene, as they went back to the edge of the woods. “I was just thinking—”
“Wait a sec.” He flapped a hand at her. “A three-foot shadow comes from a two-foot stick. So a thirty-foot shadow would come from a twenty-foot house. Right?”
“Right,” said Irene. “But listen—”
“I measured the shadow to the edge of the eaves. That’s where the top of the guest-room window comes. Now we subtract the distance from the ground to the sill of the laboratory window. About five feet. So the tube of the periscope has to be fifteen feet long. You see? It’s easy.”
Irene sighed. “It’s marvelous,” she said. “But don’t you think it would be a lot easier if you just looked through these field glasses right into the window?”
Danny opened his mouth and closed it again. Joe began to laugh.
“Oh, well,” Danny said, ruefully. “I’ve heard that girls are more practical than boys.”
Irene grinned, and handed him the binoculars. “You can have the first look, for saying such a nice thing,” she said.
Danny peered at the laboratory window for a long moment, while the other two fidgeted. Then he said, “I can see a tall metal box. It has a square plate in it, something like a television screen.”
“Let me look,” Irene said.
“In a minute. I can see some other stuff—something that looks like a computer, with dials and buttons. Oh!”
“What? What is it?” Irene was almost dancing with impatience.
“The Professor!” Danny lowered the binoculars. “He was looking right at me. He shook his fist.”
“What?” Irene snatched the field glasses. “That doesn’t sound like him at all.”
She lifted the binoculars to her eyes. Then she snorted. “I see him all right, but he isn’t shaking his fist,” she said. “He’s waving. Now he’s bending over the table and doing something with a big piece of paper. Now he’s at the outside door—he’s opened it. He’s holding up the paper. It’s got writing on it.”
“Writing? What does it say?”
Irene giggled.
“It says, ‘I surrender. Come on in,’” she replied.
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