One day Gus and George, the colored man, were working at the far end of the curved dam breast, the stone work having risen to four feet in height.  Bill was stooping to inspect the cement on the near end and the view of the hill was cut off.  Presently voices came to him, mostly a sort of good-natured protest in monosyllables; then Thad’s tones, low enough to keep Gus from hearing.

“I tell you, Uncle, they’re putting it over on you.  It ain’t any of my business, but I hate to see you having your leg pulled.”

“’Taint!” was the brief answer.

“Well, if you don’t want to think so; but I know it.  Look at this dam:  not over two feet thick and expected to hold tons of water.  Wait till a flood hits it.  Will it go out like a stack of cards, or won’t it?  And they’re not using enough cement; one-fourth only with the sand.”

“Grouting, broken stones,” growled Mr. Hooper.

“Not sufficient, as you’ll see.  And does anybody want to say that a two-inch pipe is going to run a water wheel with force enough to turn a generator that will drive thirty or forty lights?  Bosh!”

“They ought to know.”

“You think they do, but have you any proof of it?  What they don’t know would fill a libra—­”

“How ’bout that there triang—­what you call it?  They knew that.”

“Oh, just a draughtsman’s smart trick; used to catch people.  I’m talking about things that are practical.  You’ll see.  I’ll bet you these blamed fools are going to strike a snag one of these days, or they’ll leave things so that there’ll be a fall-down.  But what need they care after they get their money?”

Bill heard footsteps retreating and dying away; Mr. Hooper went over to Gus and, with evident hesitation, asked: 

“Do you reckon you’re makin’ the stone work thick enough?  It does look most terrible weak.”

“Sure, Mr. Hooper.  Bill’ll explain that to you.  Professor Gray and he worked out the exact resistance and the pressure.”

And then Bill limped over; he had left his crutch on the hillside, and he said, half laughing: 

“This wall, Mr. Hooper, can’t give way, even if it had the ocean behind it, unless the stone and cement were mashed and crumbled by pressure.  The only thing that could break it would be about two days’ hammering with a sledge, or a big charge of blasting powder, and even that couldn’t do a great deal of damage.”

“All right, me lad; you ought to know an’ I believe you.”

Mr. Hooper’s genial good humor returned to him immediately; it was evident that he was from time to time unpleasantly influenced by the soft and ready tongue of his nephew.  The old gentleman turned toward home and disappeared; a short time afterward Thad came and stood near where Gus was working, but he said nothing, nor did Gus address him.  Then the slim youth also departed and hardly half an hour elapsed before down the hill came Grace and Skeets, the latter stumbling several times, nearly pitching headlong and yet most mirthful over her own near misfortune; but little Miss Hooper seemed unusually serious-minded.  A lively exchange of jests and jolly banter commenced between Skeets and Gus, who could use his tongue if forced to; but presently Grace left her laughing chum and came over to where Bill had resumed his inspection.