"I'm no Seton-Thompson on the tracks question. Wait till David comes, he's a regular nature-faker for you. Leave him alone and he'll tell a tale of seeing a fox do the honors at a ten-course dinner with squirrels popping the champagne corks."

The cook laughed, but awaited the verdict of his comrade, who, after a prolonged examination, straightened himself, and remarked soberly:

"That's got me! You say the hambone and the bread were clean gone?"

"Clean as a whistle! There was a lot of mud on the dish, and that was all."

"Put it up to David, or Field. Field will tell us all he knows, and what's more, will explain why he doesn't know the rest; but David will put up the best yarn."

A few minutes later the rest of the party dropped in and in turn expressed surprise and conjecture about the confusing marks upon the ground until all were back except David and the chief, and shortly David appeared.

"Where's Field?" one of the men asked.

"He stayed behind a minute or two for something. He said he'd be right along. No," he continued, in answer to a question, "we didn't see anything of the boy."

"Well, it's a good thing you're here, anyway," said the cook, "for we've been waiting for you to explain a mystery that's puzzled the whole camp.

You're a woodsman, you know, and it's up to you to tell us."

"All right," said David with a confident swagger. "Trot out your mystery."

The cook led him to where the tracks were visible in the soil and related to him the theft of the hambone and the bread, concluding with:

"And what we want to know is--what kind of a critter made them tracks?"

David stooped down for a few seconds and looked at the marks on the ground, then turned around to the fellows grouped about him, and said in a tone of scorn:

"You don't know what that is?"

"No, what is it?" responded one of the men.

"Well, you're a pretty lot of lumberjacks not to know a swamp angel's work when you see one."

"Swamp angel?" queried the cook in amazement.

"Swamp angel, of course. Yes, why not? I suppose"--this in a tone of much condescension--"you have heard of a swamp angel?"

The cook grinned at him.

"You're a good one, David, all right," he said. "Go on, tell us about a swamp angel."

"Why, a swamp angel," said David, thinking rapidly, "is a cross between a flying squirrel and a flying fox----"

"With a strain of flying-fish thrown in. Go on, David," interrupted one of the men with a laugh.

"It lives only in the densest kind of swamps," went on David, ignoring the interruption, "and it is called an angel because it can fly so readily. Its chief characteristic is that it crosses its legs while walking, so that the off fore and hind leg track on the nigh side and the near ones on the off. That's what gives the tracks that peculiar look you noticed. Its usual food----"

"Is ham sandwiches," broke in the cook. "No, David, I guess the swamp angel yarn's a little strong. Here comes the chief; we'll see what he says about it."

As soon as Field arrived near the group of men, the cook started in to tell him about the theft of the food, but the chief stopped him.

"To Texas with the hambone," he said; "we've got no time to waste talking about trifles. It's up to us to find that boy without delay. I hold myself to blame in not getting after him sooner, but his last hail, it seemed to me, just before the one I sent you to find him on, was only a few yards from the camp. How, in so short a time, he could have got out of earshot, is a thing I don't understand. I only hope he hasn't put a bullet into himself somewhere with that pesky little gun of his while he was firing all those shots. Get busy at the grub, boys, because if we don't get him by the time it's dark, he may be out all night, and I don't want that."

"He can't be very far away, Mr. Field," said David.

"As long as he's out of reach, it doesn't much matter whether he's near or far. But he must be found, if it takes all night."

All through the supper the men discussed plans for the finding of the boy, but when Roger heard Field tell two of the men to start out and not return until midnight if they hadn't found the lad before then, he thought it was time to bring the jest to an end. He parted the branches over the chief's head and looked down.

Then, suddenly, the men gathered around the fire heard Roger's voice, saying in a smooth and sarcastic manner:

"I was never called an angel before, not even a swamp angel, though I'm pretty well up toward heaven in this tree. But this hambone is very dry eating, and I guess I'll come down for the b.u.t.ter and the mustard."

"You blithering idiot!" said Field, looking up angrily, though there was evidently a great relief in his voice, "get down out of that."

"Oh, very well!" said Roger with a grin, as he descended the branches of the tree. Then, coming into the circle, he added, "I thought I'd come down and help you eat that snipe that Mr. Field has just brought in!"

CHAPTER IV

IN THE GIANT TULE SWAMPS

From the time that Roger fooled the members of the party just as they were organizing a rescue search for him, his path became much easier.

Though still he occasionally made mistakes, as was unavoidable, he found they were condoned rather than exaggerated. Indeed, the boy realized that he was no longer treated as a tenderfoot, as he had been but a few weeks before, but, none the less, he was not sorry when Field told him one evening that he thought Roberts would be along shortly.

Roger was growing weary of the Minnesota work because it was evident that it consisted of the same routine day after day, that it was unremittingly hard work, and that the sense of progress was slow in proportion to the labor involved. Then the mosquitoes were beginning to get troublesome, and worst of all, the "bulldog flies" began to make their presence felt. These large horse-flies, which madden cattle and drive horses to distraction, in certain parts of the marsh were ferocious and hungry enough to attack men. Roger found that he was popular with them and got many sharp nips, which, though in no sense dangerous, were irritating and painful.

"I don't want to seem ungrateful, Mr. Field," he said, when his chief broached the return of his former co-laborer to him, "and I'm not, but Mr. Mitchon seemed to think that I would only stay a few weeks here, for the sake of the experience and to get the hang of this kind of work. I think I have gained some knowledge of it, and," he laughed, "I can shoot snipe and teach swamp angels to steal ham sandwiches."

The chief smiled in response.

"You turned the tables on us very neatly that time, Roger," he said, "and you really had me badly worried, because, as you know yourself, these swamps are not a good place to get lost in. I reckon, from what you've told me, that if you had walked heedlessly on into that quag without trying to test it step by step, you would still be there, only at the bottom instead of the top."

"I really believe I would," answered the boy seriously.

"If you stick to the Survey," went on Field, "and come to be the head of a party, particularly in wild country, you will see how necessary it is to do just what you're told instead of trying to run the thing your own way. If you follow instructions and anything goes wrong, then the fault belongs to the head of the party, who is supposed to have enough judgment and experience to know what to do in an emergency. What could have been more simple than to go twenty or thirty yards farther away than you had been told, just as you did, for instance, and yet, if you had not been lucky, you would have disappeared forever in that quagmire and by your death spoiled our record."

"Have many lives been lost in Survey work?" asked Roger.

"In the nearly thirty years of the existence of the Geological Survey, as a separate branch of the Department of the Interior," replied Field, "during which time explorations of the most extreme peril have been undertaken, only one life has been lost. Really, when you come to consider how much of the work has been done in lands absolutely unknown, and that thousands of miles of territory have been covered wherein a white man had never before set his foot, this is nothing short of astounding."

"But if sickness should strike a camp?" queried the boy.

"Hard work, clean living, good judgment, and the open air, are worth all the drugs we know about and a whole lot more that we don't. Of course a small chest of certain radical remedies accompanies each party, with quinine and things like that, but it is seldom that it is opened."

"But how about accidents, Mr. Field?"