150. _Laid_. I pause upon this word, for it is an important one. And I must devote the rest of this lecture to consideration merely of what follows from the difference between laying a stone and setting it up, whether we regard sculpture or construction. The subject is so wide, I scarcely know how to approach it. Perhaps it will be the pleasantest way to begin if I read you a letter from one of yourselves to me. A very favourite pupil, who travels third class always, for sake of better company, wrote to me the other day: "One of my fellow-travellers, who was a builder, or else a master mason, told me that the way in which red sandstone buildings last depends entirely on the way in which the stone is laid. It must lie as it does in the quarry; but he said that very few workmen could always tell the difference between the joints of planes of cleavage and the--something else which I couldn't catch,--by which he meant, I suppose planes of stratification. He said too that some people, though they were very particular [Illustration: PLATE VI.--THE STORY OF ST. JOHN. ADVENT.] [Illustration: PLATE VII.--THE STORY OF ST. JOHN. DEPARTURE.] about having the stone laid well, allowed blocks to stand in the rain the wrong way up, and that they never recovered one wetting. The stone of the same quarry varies much, and he said that moss will grow immediately on good stone, but not on bad. How curious,--nature helping the best workman!" Thus far my favourite pupil. 151. 'Moss will grow on the best stone.' The first thing your modern restorer would do is to scrape it off; and with it, whatever knitted surface, half moss root, protects the interior stone. Have you ever considered the infinite functions of protection to mountain form exercised by the mosses and lichens? It will perhaps be refreshing to you after our work among the Pisan marbles and legends, if we have a lecture or two on moss. Meantime I need not tell you that it would not be a satisfactory natural arrangement if moss grew on marble, and that all fine workmanship in marble implies equal exquisiteness of surface and edge.