CHAPTER SIX

Slide into Darkness

Although the night was damp and cloudy, the morning dawned bright and clear and the expedition hiked up through the woods under a brilliant sky. As Danny remarked, it wouldn’t make much difference to them what kind of day it was once they got underground, but it raised their spirits immensely before they started.

They found the way without difficulty, following Irene’s blazed trail. As they approached the big oak tree, Dr. Tresselt stopped and pointed to a deep gully cut in the earth like a wagon road.

“Many of these caves in limestone hills were carved out by flowing streams,” he said. “That gully shows where the stream may once have come out.”

“And there’s the cave itself,” Danny cried, in excitement.

They could see that the oak tree stood on a rocky point formed by two great slabs leaning against each other. Below was a black opening, like the entrance to a teepee. They climbed up to it, and then paused to pull on sweaters or heavy jackets.

They were all variously loaded down. Dr. Tresselt carried a powerful battery lamp belonging to the Professor; Professor Bullfinch had another such lamp and his C-ray; the three young people each wore a knapsack and carried a good flashlight. Irene had a first-aid kit in her pack, and spare batteries for all the different lamps. Joe’s knapsack was stuffed with sandwiches, chocolate bars, and cookies. Danny opened his pack and took out a square metal box with a handle at the top, a pair of earphones, and what looked like a microphone on a cable attached to it.

“Well, well,” said Dr. Tresselt. “A Geiger-Müller counter, eh? Planning to do a little prospecting for uranium?”

“I doubt there’s any around here, Danny,” said the Professor, gravely.

“It’s not for that at all,” Danny replied, checking over the instrument and replacing it in his pack. “But since this is a scientific expedition, we ought to do the whole thing scientifically. So this is for finding our way back.”

“I don’t think I quite understand,” the Professor said. “How is a Geiger counter going to help?”

“Well, I borrowed this from Professor Blum, in the Physics Department, yesterday,” Danny said. “And I also got from him some thorium nitrate crystals. They’re mildly radioactive, you know, and they’ll register on the counter and make it click rapidly. I’ve got ’em in this little box. Every time we come to a place where there’s more than one way to go, I’ll drop a few of them. Then, when we come back, we can pick up our trail with the counter. See?”

The Professor rubbed his bald head. “I see. But wouldn’t it have been easier if you had just brought along a small can of white paint and a brush?”

“Easier?” Danny shook his head, scornfully. “Gosh, no! Opening and closing a can of sloppy paint? And messing around with a brush?”

“As it happens, I brought along a piece of chalk,” Dr. Tresselt observed, mildly.

“Chalk? But gosh, Dr. Tresselt,” Danny wailed, “that isn’t scientific at all!”

“All right,” said Professor Bullfinch. “We’ll let you do it your way, Dan, since you’ve made such careful preparations. Now, are we all set?”

“Right!” said Dr. Tresselt.

“I’m ready,” said Joe. He took a notebook and a pencil out of his pocket. “Ten A.M. The expedition arrived at the cave entrance and prepared to make its way to the very center of the earth.”

“Sounds exciting,” said the Professor. “Only I don’t think we’ll be going that far down.”

“It’s what they call ‘artistic license,’” Joe explained. “I’ve decided to write a report about the trip for the school magazine, and I have to make it seem dangerous even if it isn’t.” He gulped nervously. “Anyway, I sure hope it isn’t.”

“I’m ready,” said Irene. She jingled the charm bracelet, which this morning she was wearing on her wrist. “I’m going to see if I can find something interesting to represent geology on my bracelet.”

“Let’s go, then,” said the Professor.

He stepped forward, snapping on his lamp. Danny was right at his heels, and the others pressed close behind.

They stood in a rock chamber with high, arching walls. Under the beams of their lights the wall shone like glass, and here and there clusters of white crystals flashed out. The floor was covered with loose stone and gravel. The ceiling, arched and craggy, sloped down toward the back of the cave where it was lost in darkness.

Dr. Tresselt bent and picked up what looked like a round, white pebble. “Carbonate of lime,” he said. “The result of the passage of water through the limestone.”

Irene and Joe drew close to look. Danny, after a glance, went to the back of the cave. “Professor Bullfinch,” he called, his voice echoing in the chamber. “There’s an opening here. Plenty big enough for you to stand up in.”

The Professor hastened to join him, and together they shone their lights into the space. “It’s a real tunnel, all right,” he said.

Its floor slanted steeply downward, and was covered with loose gravel. The Professor took a cautious step or two, and then said, “I can hear something trickling. There may be a stream down there.”

“Oh, boy!” Danny said. “A secret underground river!”

He darted forward. His foot slipped in the gravel, and he lost his balance. He grabbed for the nearest support, which happened to be the front of the Professor’s jacket.

The Professor went plunging down the slope, with Danny clinging to him. Somehow they managed to keep from falling. Sliding and swaying, they raced downward, their lights darting crazily as they waved their arms to keep their balance. Then, all at once, they hit a patch of wet clay.

The Professor’s heels went out from under him.

“I can’t—” he yelled.

Thump! Down he went, with Dan on top of him.

There was a long pause. At last, in a muffled voice, he finished: “—keep my balance. Would you mind taking your elbow out of my ear, Dan?”