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