"Spandrel, spandrel, ye loon," grunted David. "Ye'll no learn to be a mason if ye canna mind the names o' things. The space between the arch and the beam's filled wi' rubble and good mortar, but the weight doesna rest on that--it's mostly on the arches where we used the best of our stanes. And there's no great travel ower the brig forbye. It's different with a cathedral like yon. Ye canna build siccan a mighty wall wi' mortar alone. The water's aye searchin' for a place to enter. When the rocks freeze under the foundations they crumble where the water turns to ice i' the seams. When the rains come the water'll creep in if we dinna make a place for it to rin awa' doon the wa'. That's why we carve the little drip-channels longways of the arches, ye see. A wall's no better than the weakest stane in it, lad, and when you've built her you guard her day and night, summer and winter, frost, fire and flood, if you want her to last. And a Minster like York or Lincoln--the sound o' the hammer about her walls winna cease till Judgment Day." Barty looked rather solemnly at the little, solid, stone-arched bridge, and the stone-walled culvert. While it was a-building David had explained that if the stream overflowed here it would be over the reedy meadows near the river, which would be none the worse for a soaking. The orchards and farm lands were safe. The work that they had done seemed to link itself in the boy's mind to cathedral towers and fortress-castles and the dykes of Flanders of which David had told. The loose stone from the ruined wall was used to finish a wall in a new place, across the corner of the land by which the river still flowed. This would make a wharf for the boats. "This mortar o' yours might ha' balked the Flood o' Noah, belike," said Farmer Appleby, when they were mixing the last lot. "I wasna there, and I canna say," said David. "But there's a way to lay the stones that's worth knowing for a job like this. Let's see if ye ken your lesson, young chap." David's amusement at Barty's intense interest in the work had changed to genuine liking. The boy showed a judgment in what he did, which pleased the mason. He had always built walls and dams with the stones he gathered when his father set him at work. His favorite playground was the stone-heap. Now he laid selected stones so deftly and skillfully that the tiny wall he was raising was almost as firm as if mortar had been used. "You lay the stones in layers or courses," he explained, "the stretcher stones go lengthwise of the wall and the head-stones with the end on the face of the wall, and you lay first one and then the other, 'cordin' as you want them. When the big stones and the little ones are fitted so that the top of the layer is pretty level it's coursed rubble, and that's better than just building anyhow." "What wey is it better?" interposed David.