ten o'clock Sam harnessed up again, and shortly before noon our travellers left the waterway by which they had travelled hitherto, and passed out to the right through a cut, less than a quarter of a mile long, where a rising lock took them into the Stratford-on-Avon Canal.
Said Sam as he worked the lock, the two children standing beside and watching:
"Now see here, when you meet your clever friend Bill, you put him two questions from me. First, why, when the boat's through, am I goin' to draw the water off an' leave the lock empty?"
Before Tilda could answer, Arthur Miles exclaimed:
"I know! It's because we're going uphill, and at the other locks, when we were going downhill, the water emptied itself."
"Right, so far as you go," nodded Sam. "But why should a lock be left empty?"
The boy thought for a moment.
"Because you don't want the water to waste, and top gates hold it better than lower ones."
"Why do the top gates hold it better?"
"Because they shut with the water, and the water holds them fast; and because they are smaller than the bottom gates, and don't leak so much."
"That's very cleverly noticed," said Sam. "Now you keep your eyes alive while we work this one, an' tell me what you see."
They watched the operation carefully.
"Well?" he asked as, having passed the Success to Commerce through, he went back to open the lower paddles—or slats, as he called them.
"I saw nothing," the boy confessed disappointedly, "except that you seemed to use more water than at the others."
"Well, and that's just it. But why?"
"It has something to do, of course, with going up-hill instead of down.... And—and I've got the reason somewhere inside my head, but I can't catch hold of it."
"I'll put it another way. This boat's mod'rate well laden, an' she takes more water lockin' up than if she was empty; but if she was empty, she'd take more water lockin' down. That's a fac'; an' if you can give me a reason for it you'll be doin' me a kindness. For I never could find one, an' I've lain awake at nights puzzlin' it over."
"I bet Bill would know," said Tilda.
Sam eyed her.
"I'd give somethin'" he said, "to be sure this Bill, as you make such a gawd of, is a real person—or whether, bein' born different to the rest of yer sex, you've 'ad to invent 'im."
Many locks encumber the descending levels of the Stratford-on-Avon Canal, and they kept Sam busy. In the intervals the boat glided deeper and deeper into a green pastoral country, parcelled out with hedgerows and lines of elms, behind which here and there lay a village half hidden—a grey tower and a few red-tiled roofs visible between the trees. Cattle dotted the near pastures, till away behind the trees—for summer had passed into late September—the children heard now and again the guns of partridge shooters cracking from fields of stubble. But no human folk frequented the banks of the canal, which wound its way past scented meadows edged with willow-herb, late meadow-sweet, yellow tansy and purple loosestrife, this last showing a blood-red stalk as its bloom died away. Out beyond, green arrowheads floated on the water; the Success to Commerce ploughed through beds of them, and they rose from under her keel and spread themselves again in her wake. Very little traffic passed over these waters. In all the way to Preston Bagot our travellers met but three boats. One, at Lowsonford Lock, had a pair of donkeys ("animals" Sam called them) to haul it; the other two, they met, coming up light by Fiwood Green. "Hold in!" "Hold out!" called the steersmen as the boats met. Sam held wide, and by shouts instructed Mr. Mortimer how to cross the towropes; and Mr. Mortimer put on an extremely knowledgeable air, but obeyed him with so signal a clumsiness that the bargees desired to know where the Success to Commerce had shipped her new mate.
The question, though put with good-humour, appeared to disturb Sam, who for the rest of the way steered in silence. There are three locks at Preston Bagot, and at the first Mr. Mortimer took occasion to apologise for his performance, adding that practice made perfect.
"I wonder, now," said Sam delicately, "if you could practise leavin' off that fur collar? A little unhandiness 'll pass off, an' no account taken; but with a furred overcoat 'tis different, an' I ought to a-mentioned it before. We don't want the children tracked, do we? An' unfort'nitly you're not one to pass in a crowd."
