spot where this odd encounter took place was some distance from any town, but a bicycle leaning against a tree at the roadside showed how the little man had got there.

"Say, would you mind letting us get by?" asked Jack.

The little man raised a hand protestingly.

"I'll be delighted to in just a moment," he said, "but just now it's impossible. You see, I've just discovered a vein of what I believe to be Laurentian granite running across the road. I am trying to trace it and—what's that? Good gracious! Back up your machine, please. I believe it runs under your wheel. I must make sure."

Jack obligingly threw in the reverse to humor the little man, who darted forward and began scraping up the dust in the road with his hands as if he had been a dog scratching out a rabbit hole. He began chipping away eagerly with his hammer at some rock that cropped up out of the road.

He broke off a piece with his hammer, which was an oddly shaped tool, and drawing out a big magnifying glass scanned the chip intently. He appeared to have forgotten all about the waiting boys. But now he seemed to remember them. He looked up, beaming.

"A magnificent specimen. One of the finest I have ever seen. Most remarkable!"

And with that he popped the bit of stone into his bag, which the boys now saw was filled with similar objects.

"Maybe he'll let us get by now," remarked Tom, but a sudden exclamation from Dick Donovan cut him short.

"Why, hullo, professor," he said, "out collecting specimens?"

The little man peered at him sharply. And then broke into a smile of recognition.

"Why, it's Dick Donovan!" he beamed, hastening up to the car, "the young journalist who wrote an article about my specimens once and woefully mixed them up. However, to an unscientific mind——"

"They are all just rocks," finished Dick with a grin.

"I have had unusual success to-day," said the professor, who appeared not to have heard the remark. "I must have at least fifty pounds of specimens on my back at this minute."

He broke off suddenly. The next moment he darted off to the side of the road and chipped off a fragment of rock from a bank that overhung it.

"This is lucky, indeed," he exclaimed, holding it up to the light so that some specks in the gray stone sparkled. "An extremely rare specimen of mica that I had no idea existed in this part of New England."

The odd little man opened his bag and introduced his latest acquisition into it While he was doing this Dick had been explaining to the boys:

"He's a queer character. Professor Jerushah Jenks. They say he's a great authority on mineralogy and so on. I interviewed him once. He's always out collecting."

"Does he always carry a quarry like that around on his back?" asked Tom.

"Always when he's getting specimens," Dick whispered back.

By this time the professor, his eyes agleam over his latest discovery, was back at the side of the car.

"Ah, my beauty, I have you safe now," he said, patting the side of the bagful of specimens. "Boys, this is my lucky day."

The boys could hardly keep from smiling at the little man's delight. It appeared hard to believe that anyone could find pleasure in packing about a sackful of heavy rocks on a hot day. But the professor's eyes were sparkling. It was clear he considered himself one of the most fortunate of men.

Dick introduced the boys and, to their surprise, the professor declared that he had read of their various adventures and inventions.

"We are actually fellow adventurers in the field of science," he cried, rattling his bag of specimens enthusiastically. "Some time I should like to call on you and see your workshops."

"You will be welcome at any time," said Jack cordially, and then the professor declared that he must be getting home.

"If we are going your way we can give you a ride," said Tom.

"Thank you, I'll accept that invitation. But what an odd-looking automobile you have there."

The boys explained to him that it was a new type of car that they were trying out for the first time and then Dick helped the scientist lift his bicycle into the tonneau. He would have helped him with his weighty load of specimens, but the professor refused to be parted from them. As they started off again he sat with the bag firmly gripped between his knees, as if afraid someone would separate him from it.

The professor lived with a spinster sister to whom his specimens were the bane of her life. As the car rolled swiftly along, he occupied his time by peeping into the bag at frequent intervals to see that none of the specimens, by some freak of nature, flew out.

All at once he reached forward and clutched Jack by the shoulder.

"Stop! My dear young friend, please stop at once!"

"What's the matter?" asked Jack, slowing down at the urgent summons.

"Look! Look there at that rock!"

To Jack the rock in question was just an ordinary bit of stone in a wall fencing in a pasture in which some cattle were grazing. But evidently the professor thought otherwise.

"It's a fine specimen of green granite," he exclaimed. "I must have it. How did such a fine piece ever come to be placed in a common wall?"

The car having now been brought to a stop, he leaped nimbly out, clutching his geological hammer in one hand and his precious sack of specimens in the other. He rushed up to the wall and stood for a minute with his head on one side, like an inquisitive bird.

"Too bad. That stone's a large flat one and goes right through the center of the wall," he mused. "The wall must come down."

And then, to the boys' consternation, he began demolishing the wall, pulling down the stones and throwing them right and left.

"Professor, you'll get in trouble," warned Dick in alarm. "Those cattle will get out. The farmer will be after us."

But the professor paid not the slightest attention. Taking off his coat, he resumed his operations with even greater vigor than before. The cattle in the field eyed him curiously. Then they began to move toward him. In front of the rest of the herd was a big black-and-white animal with sharp horns and big, thick neck.

It gave a sudden bellow and then rushed straight at the considerable gap the man of science had made in the stone fence.

"It's a bull!" yelled Dick suddenly. "Run, professor! Run or he'll toss you!"

With lowered horns the bull rushed down upon the unconscious scientist at locomotive speed. But the professor was oblivious to everything else but uncovering the odd-looking green stone embedded in the heart of the wall.

The boys shouted to him but he didn't hear them. On rushed the bull, bellowing, charging, ready to annihilate the scientist.

"Run!" yelled the boys at the top of their lungs. "Run!"

But the professor, with his precious bag in one hand and his hammer in the other, stood staring at the advancing bull through his thick glasses as if the maddened creature had been some sort of new and interesting specimen.

"Gracious! He's a goner!" groaned Dick.