When, in the evening, Paul’s report of the lesson was read in the family circle, M. de Gandelau interrupted the reading at this phrase incorrectly given, “Good is only the absence of evil.”
“Oh, oh!” said his father; “Charity is something more than the absence of evil. If you give nothing to the poor man who asks bread of you; if, being able to swim, you do not try to save a drowning man, you do not do evil, but certainly you do not do good.”
“That is not exactly what I said to Paul,” replied Eugène, smiling. “Respecting defects discovered in building, I said, ‘I believe that the good is the absence of the bad;’ that is to say, in building operations, and perhaps in many other matters belonging to the purely material order of things, to avoid what is bad is to do well, but not to do good. I must, however, admit that I did not sufficiently develop my thought.
“Two things are needed to make a good builder: clear-sighted intelligence—which depends on our individual psychical nature—and the experience we acquire.
“Observation and experience thence resulting enable us to recognize what is defective and to avoid it; but if, notwithstanding the advantage thence derived, we are not endowed by nature with clear-sighted intelligence, experience, though enabling us to avoid the bad, does not of itself suffice for the discovery of the good.
“Moreover, though in morals the good is absolute and independent of circumstances, it is not the same with building. What is good here is bad elsewhere, on account of climate, habits, nature of materials, and the way in which they are affected by local circumstances. While, for instance, it is desirable to cover a roof with slates in a temperate and humid climate, this kind of roofing is objectionable in a warm, dry, and windy climate. Wooden buildings will be excellent in one situation and unsuitable in others. While it is desirable to admit the light by wide openings and to glaze large surfaces in northern climates, because the sun’s glare is subdued, this would be objectionable in southern countries, where the light is intense, and where it is necessary to procure shelter from the heat. A code of morals is possible, but we cannot establish absolute rules in building; experience, reasoning, and reflection must therefore always be summoned to our aid when we attempt to build. Very often young architects have asked me what treatise on building I should recommend as the best. There is none, I tell them; because a treatise cannot anticipate all contingencies,—all the special circumstances that present themselves in the experience of an architect. A treatise lays down rules; but ninety-nine times out of a hundred you have to encounter the exception and cannot rely upon the rule. A treatise on building is useful in habituating the mind to devise plans and have them put into execution according to certain methods; it gives you the means of solving the problems proposed; but it does not actually solve them, or at least only solves one in a thousand. It is then for intelligence to supply in the thousand cases presented what the rule cannot provide for.”
Lesson the Third.
“Yesterday,” said Eugène to Paul, when the latter came into his room, “we visited the cellars and the ground floor; now we shall take a walk among the garrets of the château. But first I must show you what is meant by a roof truss. The simplest truss (Fig. [13]) is composed of four pieces of wood: two principal rafters, a tie-beam, and a king-post. The two inclined pieces A are the blades; the horizontal piece B is the tie-beam, and the vertical piece C the king-post. The upper ends of the blades meet in the king-post, as I show you in the detail D,—namely, by the means of two tenons E, which fit into two mortises F, and a shoulder G, which make the whole pressure of the timber bear into the notch I. The lower ends of the blades are similarly connected at the two extremities of the tie-beam, as this other detail H shows us. The king-post is also connected by a tenon, in the centre of the tie-beam, but loosely, and without bearing upon this tie-beam. When the tenons are let into the mortises, pegs of wood are driven into the holes marked to fasten the whole well. The more pressure there is on the top, M, the more the two blades tend to spread at the foot; but these, being fixed at the two ends of the tie-beam, tighten the latter like the string of a bow. The more this tie-beam is strained, therefore, the less it is inclined to bend, and the object of the king-post is only to suspend it by its centre, and to connect the heads of the blades. But between M and N these rafters may bend under the weight of the roof covering; two struts, O P, therefore are added, which arrest this bending by bringing the pressure to bear on the king-post, so that the latter is in its turn strained between M and P. As wood will not stretch, the point P is fixed, and the two points O likewise.
Fig. 13.