"He was too fond o' making rubble serve for buildin' stone," said David. "Then he'd face it with Portland ashlars to deceive the passer-by." "Ye'll have no cause to worry over that here," said Ralph Appleby dryly. "I'm not using ashlars or whatever ye call them, in my orchard wall. Good masonry will do." "Ashlar means a building stone cut and dressed," explained David. "I went along that wall of yours before you came. If you make a culvert up stream with a stone-arched bridge in place of the ford yonder, ye'll divert the course of the waters from your land." "If I put a bridge over the Wash, I could make a weir to catch salmon," said the startled farmer. "I've no cut stone for arches." "We'll use good mortar and plenty of it, that's all," said David. "I'll show ye." The things that David accomplished with rubble, or miscellaneous scrap-stone, seemed like magic to Barty. He trotted about at the heels of the mason, got very tired and delightfully dirty, asked numberless questions, which were always answered, and considered David the most interesting man he had ever met. David solved the building-stone problem by concocting mortar after a recipe of his own and using plenty of it between selected stones. Sometimes there seemed to be almost as much mortar as there was stone, but the wedge-shaped pieces were so fitted that the greater the pressure on the arch the firmer it would be. Laborers were set to work digging a channel to let the stream through this gully under the arches, and it seemed glad to go. "When I'm a man, David," announced Barty, lying over the bridge-rail on his stomach and looking down at the waters that tore through the new channel, "I shall be a mason just like you. The river can't get our apples now, can it?" David grinned. "Water never runs up hill," he said. "And it will run down hill if it takes a thousand years. You learn that first, if you want to be a mason, lad." "But everybody knows that," Barty protested. "Two and two mak' four, but if you and me had twa aipples each, and I ate one o' mine, and pit the ither with yours to mak' fower and you didna find it out it wad be a sign ye didna know numbers," retorted David, growing more and more Scotch as he explained. "And when I see a mason lay twa-three stones to twa-three mair and fill in the core wi' rubble I ken he doesna reckon on the water seeping in." "But you've put rubble in those arches, David," said Barty, using his eyes to help his argument.