After looking attentively at it for some time, he said to the boy, who, interested in whatever attracted his father's attention, was looking over his shoulder,—
"Clem, the lines on that paper are a screw."
"Be they, father?"
"Unpin the paper."
Clem did so, and they were all straight again.
"How funny, father!"
"Get my square, and you, Robert, go to the wood-pile and get a piece of birch bark—white birch."
After stripping the bark to a thin sheet, he cut it square. He then set off an inch at one corner, and drew a line from that mark to the corner of the paper on the same side, making an oblique line.
"You see that is up hill, boys—don't you?"
"Yes, father."