viz., revenge.

In the rear of the schoolhouse, there stood an old wood-shed. For some
slight offence the teacher had, two or three years back, made Belton
the fire-maker for the balance of his school life instead of passing
the task around according to custom. Thus the care of the wood-house
had fallen permanently to Belton's lot.

During the last year Belton had dug a large hole running from the
floor of the wood-shed to a point under the platform of the school
room. The dirt from this underground channel he cast into a deep old
unused well, not far distant. Once under the platform, he kept on
digging, making the hole larger by far. Numerous rocks abounded in the
neighborhood, and these he used to wall up his underground room,
so that it would hold water. Just in the middle of the school-room
platform he cut, from beneath, a square hole, taking in the spot where
the teacher invariably stood when addressing the school. He cut the
boards until they lacked but a very little, indeed, of being cut
through. All looked well above, but a baby would not be safe standing
thereon. Belton contrived a kind of prop with a weight attached. This
prop would serve to keep the cut section from breaking through. The
attached weight was at rest in a hole left in the wall of the cavity
near its top. If you dislocated the weight, the momentum that it would
gather in the fall would pull down the prop to which it was attached.

Finally, Belton fastened a strong rope to the weight, and ran the rope
under the schoolhouse floor until it was immediately beneath his seat.
With an auger he made a hole in the floor and brought the end through.
He managed to keep this bit of rope concealed, while at the same time
he had perfect command of his trap door.