BEFORE the blaze in Bob’s eyes the man shrank back, hesitated a moment, and then turned in the direction of the freight station.

“All right,” he snarled. “But don’t let me catch the kid around here again, or you either.”

He walked up the track to the end of the train, then disappeared behind the engine.

“Gee, that was swell of you,” said Spike to Bob. “You sure had that guy scared.”

“He was glad enough to get out of it,” laughed Joe. “Old Bob wouldn’t have left a grease spot of him.”

“But now,” began Bob, anxious to turn this tribute aside, “let’s figure out what to do. I suppose the only thing——”

“I want to get home,” Spike interrupted. “I may have something comin’ to me, but the sooner I get it over, the better.”

“Where do you live?” Joe asked.

“Only about a half-mile from here.”

Joe got a piece of paper and pencil out of his pocket. He tore off one corner and wrote down the address of himself and his friend. This he gave to Spike.

“Here,” he said. “Write us a letter some time. Now where do you live?”

Spike told him, and then, with a warm good-bye, he left the youths and hurried down the track.

Bob and Joe watched the lad until he disappeared from view. Even after they lost sight of him, they stood gazing in that direction until a locomotive whistle roused them.

“He’s a good kid, all right,” smiled Bob. “Might be an aimless wanderer, but he has a lot in him.”

“Got a keen sense of humor, too,” said Joe, and then added: “I wonder if he’ll really go to school and make something out of himself, as he said he would?”

“Hard telling. A lot can happen to change his mind, you know.”

For several minutes Bob and Joe watched the busy scene about the tracks. Finally a factory whistle from afar prompted Joe to glance at his watch.

“Nearly two o’clock,” he announced. “Come on. Let’s hurry down to the freight station and see if we can send a telegram to our folks. If we hadn’t lost the car in that river, we would have been home several days ago.”

The youths moved down to the building and went inside. After making several inquiries they finally found the main office, where they were permitted to send a telegram. Then they left the building and walked in the direction of the street.

“Good old Chicago,” smiled Joe. “It’s only been a couple of months since we were here.”

Bob stopped suddenly.

“That reminds me,” he started. “We came here with our dads to see a Mr. Wallace, who’s with the Museum of Natural History, didn’t we? And this Mr. Wallace is planning on going with our dads’ expedition to the Andes Mountains, isn’t he? Do you suppose he’s left for Washington yet?”

Joe’s face lightened.

“I see what you mean,” he said. “We can go and see him, and incidentally we can borrow enough money to get home on. Suppose we go to the museum now.”

The boys were familiar with Chicago and had no difficulty in taking a street car. After a half-hour’s ride they got off within a few squares of the museum. A ten-minute walk brought them to the main entrance.

At the office they made inquiries about Mr. Wallace and finally found him in a laboratory on the second floor. He smiled broadly as he recognized Bob and Joe.

“Well, this is an unexpected pleasure,” he said, extending his hand. “What, may I ask, are you fellows doing in Chicago? Why aren’t you getting ready for that Andes expedition?”

“It isn’t our fault that we’re here,” laughed Bob, and then proceeded to tell of the events that led to their presence. “Since we finally landed here, we thought we’d come to the museum and see if you had left for Washington yet,” he concluded.

“A strange chain of circumstances,” the scientist breathed. “Not many could go through all that in the course of a few days. No doubt it was your first experience as hoboes, was it not?”

“First and last,” returned Joe. “We’ve had all we want of it. But now,” he went on, “when are you going to Washington? The expedition leaves in little more than a week.”

“I had planned to go day after tomorrow,” Mr. Wallace said. “I think everything will be in readiness by that time. I’d like to spend at least three days in Washington talking with your fathers and others of the expedition before sailing. Of course you fellows are familiar with the details of the expedition, are you not?”

“Quite the contrary,” returned Bob. “You see, when the matter was first mentioned, about a month ago, there was not much known about it. Our dads declined to say much, because they were not absolutely sure they were going. Joe and I, though, had a sort of feeling that they were going, and finally got permission to stay out of college at least a half-year.”

“So you could go with the expedition?” interrupted the scientist.

Bob nodded.

“We figured we’d get as much good out of such a trip as we could get in a university,” he explained. “Then, too, there’s a chance of making money by taking motion pictures, as we did on our other expeditions.”

“I think you did wisely,” Mr. Wallace said. “It usually isn’t good for a fellow to get out of college too young. When an extraordinary chance like this turns up, it’s best to take it.”

He motioned for the boys to follow him into his office, where several chairs were arranged about the desk. A large bookcase occupied a whole end of the room, while opposite it was a case of instruments and preservatives.

“Sit down,” he directed them, “and we’ll talk over this Peruvian expedition.”

Bob and Joe did as directed, glad of the chance to rest their tired limbs.

Mr. Wallace procured an atlas, opened it to a map of Peru, and drew an imaginary line in the lower right-hand corner.

“Here’s Cuzco,” he pointed out. “We’ll probably make it or some other near-by city our base. From there we’ll go into the Andes Mountains on our varied scientific quests.”

“But what—what is the main purpose of the expedition?” inquired Joe. “Of course, you and Mr. Holton and Dad are naturalists, who want to get specimens of animal life. But that isn’t the chief aim of the expedition, is it?”

“No. It is being sent out by the division of ethnology at the museum in Washington. The scientists in that field have in mind mainly to study the ruins of the vanished Inca civilization. Those Indians, you know, that built so many marvelous works of architecture. That’s about as much as I know about them, though,” he laughed. “My line runs straight through the field of natural history and zoÖlogy, and incidentally anatomy, histology, taxonomy, embryology, ecology——”

“That’s enough!” interrupted Bob, smiling sheepishly. “You don’t expect Joe and me to be acquainted with all those subjects, do you? We’re pretty good shots, but as scientists we’re as yet a complete flop.”

A general laugh ensued, after which the naturalist again pointed to the map.

“We are to explore the region northwest of Lake Titicaca,” he continued. “I understand there are some very high peaks in this range, all the way from ten to twenty thousand feet in altitude.”

“These Incas,” started Joe, “when did they live? It hasn’t been so very long ago, has it?”

“Not as time is usually thought of. The sixteenth century witnessed their downfall. This was at the time of the Spanish South American explorations, you know.”

“Those Spaniards sure saw something unusual and unexpected,” remarked Bob. “This mountainous region was chock-full of architectural wonders, all built by the Incas.”

“Something tells me we’ll see sights, all right,” said Joe. “It will be good to get away from home again—into the unknown, I mean. And that reminds me. Would it be possible for you to lend us enough money to get back to Washington?”

“Why—of course. How much do you need?”

“Fifty dollars will pull us through. Perhaps we can get along on less than that,” was the answer from Bob.

“All right. I’ll see that you get it. But wait! I expect to go day after tomorrow with a friend, who is driving East on business. There will be plenty of room for two more. You fellows don’t have to get home at once, do you?”

“No, we don’t have to,” returned Joe. “We——”

“Suppose you be my guests until then. I’ll be only too glad to have you. In the meantime we can be discussing the coming expedition.”

“We’d sort of hate to do that,” Bob said. “It will mean a lot of trouble to you.”

“Forget it! I’ll be only too glad to have you.”

“Well, all right, if you——” Joe began.

“We’ll call it settled,” Mr. Wallace said. “And now, since my day is practically over, we may as well go to the house. That is, if you’re ready.”

“We’re ready any time,” Bob told him.

The three went outside, to a place where the naturalist’s automobile was parked. All got inside and drove through the city till they came to a beautiful suburb.

“Here’s my place,” said Mr. Wallace, pointing to a large house of rather costly design.

Inside, the youths were introduced to Mrs. Wallace, who made them feel perfectly at home.

“I hate to see Mr. Wallace leave on an expedition,” she said, “but I can appreciate his interest in science. In fact, I have often wished I could accompany him. Be a sort of Mrs. Martin Johnson, you know.”

“I wish our mothers were like that,” laughed Bob. “If they were, perhaps Joe and I wouldn’t have so much difficulty in getting their consent to go with our dads.”

A bountiful dinner was soon served, Bob and Joe eating heartily.

“And now I have a surprise for you,” Mr. Wallace said, when the meal was over. “It is something I know we all will enjoy, especially in view of what is to come.”

The young men looked inquiring.