Chapter V: Paul Pursues a Course of Study in Practical Architecture

Meantime, letters and newspapers were daily bringing the most distressing intelligence. The enemy had crossed the French boundary a week ago. Building was a matter scarcely to be thought of. M. de Gandelau was visited almost incessantly by country people coming to impart to him their fears and to ask his advice. The able-bodied youths of the district were summoned to be incorporated in the _mobile_. The manufactories of the neighbourhood were being closed for want of hands. Groups of peasants—men and women—might be met on the roads, who, contrary to the quiet habits of this province, were speaking in excited tones; some of the women were crying. The labours of the fields were suspended; a painful shudder seemed to pass through the country; lights were seen in the cottages at a late hour of the night; voices were heard calling to each other. The cattle were brought in earlier than usual, and were driven afield later in the morning. When people met each other on the roads they would stay long talking. Sometimes, instead of returning to their own abodes, they would walk rapidly on together in the direction of the neighbouring town.

It was the 20th of August, 1870, when, going into his father’s room early in the morning, Paul found him still more depressed than on the previous days and it was not merely his aggravated gout that caused the depression. Eugène was there.—“Some are too old, others too young. If this boy was four or five years older,” said M. de Gandelau, embracing his son, “I would send him with all these young fellows who are summoned to the service; but he is too young, happily for his mother. It will be a long struggle, they say; God only knows what will become of our poor country engaged in an insensate war; but our duty is clear—to remain here among all these families, distressed as they are, and bereaved of their children; to wait, and try to calm down this distracted multitude. Do not let us surrender our self-possession, or give way to useless disquietude; let us work—that is the remedy for all evils; and misfortune will not find us more destitute of courage after days of labour than after a period of feverish inactivity. I see that Paul will not be able to return so soon to college. As to yourself, Eugène, nothing obliges you just now to stay in one place rather than another. Your business will be suspended in every quarter; remain here, where you can make yourself useful as long as the country does not require your services.

“Who knows what may happen! But even if this state of things continues, we will try to build Marie’s house; it will give employment to those who have been thrown out of work. You will be able to give Paul practical lessons in the elements of construction. We shall, perhaps, run short of the one thing needful for building—money. Ah, well! that will oblige us to discover the means of doing without it. We have the raw material; we have hands, and enough to keep them for some time to come. Let us, then, not give way to despondency and useless recriminations; let us work; we shall be only the better prepared if in one last effort we have to call upon all—old men and children with the rest—to defend our native soil.”

Madame de Gandelau uniting her entreaties with those of her husband, it was not difficult to persuade Eugène to take up his quarters at the _château_. In fact, three days subsequently, after having gone away to settle some affairs, he was on his way back with an ample store of paper and instruments required for the details of a building plan.

They could not set to work till the sketch sent to Paul’s sister should be returned, approved or amended. It was decided that during the interval Eugène should give Paul the first notions of the building of a house, that the morning should be the time for instruction, and that in the afternoon our architectural tyro should reproduce the lesson in writing, and have his work corrected at the family gatherings in the evening. Thus the days would be well occupied.

LESSON THE FIRST.

“If you please, Paul, we will take our lessons walking, and for a good reason.”

This arrangement was quite satisfactory to Paul, who was certainly not accustomed to this mode of teaching at the Lyceum. The prospect of a course of lessons delivered, re-produced in writing by the pupil, and corrected _indoors_, had not seemed to him at the first blush quite to harmonize with the idea which a youth of sixteen forms of hours consecrated to recreation; and although after his first attempts architecture seemed to him a very noble study, and he was proud enough to think that _his plan_ was perhaps at this moment being inspected by his sister Marie and her husband, yet, at the moment he was directing his steps towards his cousin’s apartment, he had looked with a somewhat longing eye at the fine old trees in the park, and the brilliant green of the meadows between their dark trunks. A sigh of satisfaction escaped him as he tripped down the steps.

“Let us proceed leisurely towards that part of the estate where we are to build the house,” said his cousin, as soon as they were outside; “a knowledge of the ground is indispensable to the architect’s further progress. There are, as you know, several kinds of soils; some resisting, others soft and compressible in various degrees. Rocks form the firmest foundation—one on which we may build with confidence—provided they have not been excavated or disturbed. The name of _virgin soil_ is given to that which presents itself in the condition in which geological phenomena have placed it; that of ‘made ground’ to soil which has been disturbed or deposited by man, or produced by vegetation, or brought to the spot by the sudden violence of torrents. As a general rule, we should give an exclusive preference to virgin soils; yet even some of these must be mistrusted, as I shall explain to you directly.

“We must then endeavour to distinguish a virgin soil from ‘made’ or disturbed ground; and to do so, some acquaintance with elementary geology is indispensable. Thus, the crystalliform rocks, granites, gneiss, and crystalline schists remain in the condition in which the cooling of the globe and the upheavals of its crust have placed them. The sandstones, the calcareous rocks, the marls, the gravels, even the clays deposited by water under an enormous pressure, are stratified—that is to say, deposited in layers, like the courses of a building, and present an excellent foundation. The hill there on the right, in whose direction your sister’s wood extends, presents, as you see from this point, escarpments laid bare by the waters of the brook we are going to cross; observe that the stone, which seems denuded, presents itself in almost horizontal layers. It is an oolitic limestone, excellent for building, and on which you may confidently rely as a foundation also. In these strata, therefore, we may excavate cellars, and make use of what we have taken from the excavations to raise the walls. Here we are walking on sandy clays, intermingled with millstone grit. This also forms a good and incompressible foundation. It is otherwise with pure clays; not that they are compressible, but, if they are not secured—if, for instance, they lie on a declivity—they are liable to slip in consequence of the infiltration of water between their layers, and the house built on them goes down with them. And thus you may sometimes see whole villages built on clayey declivities, descending into the valley. Great attention, therefore, must be paid to the method in which you build in clays, if you would avoid these dangers. Sometimes also, when they are greatly compressed by a heavy building, the clays sink down under the weight, and rise proportionally at a little distance, in see-saw fashion. Marine sands, pure, fine or gravelly, are well adapted to receive foundations, because the sand settles naturally, however slightly moistened it may be. To such a degree is this the case, that we can form an artificial foundation if needful by depositing good beds of sea-sand on a questionable soil, and moistening these beds thoroughly. The finer the sand is and the freer from clay the better, for its small, hard, equal grains leave only very slight intervals between them and touch on several points. If the weight compresses the layer of sand, and forces it to settle down, the settling down is regular, and consequently harmless. The building settles thus to the extent of some fractions of an inch, according to its weight; but it does not dislocate, because it settles uniformly. The alluvial deposits formed by slowly-flowing waters, such as rivers or lakes, also compose good foundations, because the layers of gravel or mud have been gradually deposited, and are closely heaped together by the liquid that transported them. It is quite otherwise with marshy soils, for the water, having no current, has allowed vegetables to grow in its bed. These vegetables on dying are annually replaced by others. Successive layers of detritus are then formed under very trifling pressure, leaving between them innumerable cavities, just like a heap of rotten hay. These deposits are called peat-bogs. Nothing can be safely placed on these deposits, for they sink down under the lightest burden. Stop! here we are near the stream, at a point which exhibits this phenomenon. Stamp on this closely-turfed soil. You perceive that the ground sounds hollow, and shakes beneath the shock. Sometimes these peat-beds reach to such a depth, through the accumulation of vegetable detritus, that the bottom can scarcely be reached. If you build upon these, your construction will gradually sink, often unequally, on account of the inclination of the sub-soil, so that the building will lean to one side. It is thus that at Pisa and at Bologna, in Italy, there are towers which inclined thus while they were being built, until the turf was completely compressed under their weight. When these soils occur, the turf must be removed, the rock or gravel must be reached, or piles must be driven in very close to each other, until they can be forced no deeper. Then, on the heads of these piles is placed what is called a raft, a kind of wooden framing, between the spaces of which concrete is poured, and on which the first courses of masonry are placed. Whole cities are built thus. Venice and Amsterdam rest only upon forests of piles driven in mud, which is spongy, because it was formed under a shallow sheet of water which had not power to compress it.

“But it is not enough to know the nature of the soil on which a building is to be erected; we must also examine the subjacent water-courses, and how the rain-water flows off on the surface of the ground, or beneath it. The presence of a bed of clay, however thin, between strata of limestone, grit or sand, is a most important fact to the builder; for such beds being impervious—that is, not allowing the rain-water to penetrate them—give rise to currents or sheets of water, which may occasion most disastrous consequences to the foundations. Examine this greenish layer just here, along the escarpment;—it is of clay; it is very thin, and cannot retain water; but suppose it were 20 inches thick. The rains, which will easily penetrate the gravel placed above, will be arrested by this layer of clay, and pursue their course along its plane of inclination, and they will gradually form cavities like small grottoes, and a concealed current. If you build a cellar wall or a foundation descending below that accumulation of water, it will reach your wall and penetrate it, in spite of your efforts, and will fill your cellars. It will consequently be necessary at the outset to divert this accumulation of water by collecting it in a drain to keep it away from your buildings. Give me your note-book, that I may show clearly what I mean by a sketch—(Fig. 6). Let A B be the stratum of clay, C D the pervious stratum of gravel or sand. A sheet of water running from E to F will be formed after every shower. This sheet will be arrested by the foundation or cellar wall G H, and will soon permeate it, since it cannot reascend nor penetrate the clay. We must, therefore, provide, at I, a transverse drain, with openings on the upper side, through which water will find its way into the channel shown in sketch K. This drain will take the water thus collected wherever you like, and leave the wall G H perfectly dry. You understand, don’t you?

“But if you have to lay your foundations entirely in clay, you must adopt much more serious precautions: for, as I told you just now, the whole bed of clay may chance to slip.

“Banks of clay are apt to slip, especially when they present such a section as I have drawn—(Fig 7). Let A be a bed of rock, B a bed of clay. Rain-water falling on the upper side from D to C, will pass at C below the bed of clay; and if the rain is persistent, it will form from C to E a soft, slippery, soapy stratum, so that the clay bed C B E will slide over it by its own weight, but especially if at G you have burdened it with a building.

“How, then, can we guard against the danger? First, by collecting the water at C into a sewer, or a dry stone drain, so that it may not pass under the clay bed,—in case the latter is very thick. Secondly, if it is only a few yards thick, by getting down to the rock or gravel for the foundation wall, and placing a collecting sewer at I, as above. Then the triangular bed of clay, C I K, will not be able to slide, being kept up by the firmly-planted and loaded wall. The part of the clay lying below, not being moistened from above, will not slip. But this wall, H, and its drain, I, must be thick enough to resist the pressure of the triangle C I K.

“You perceive, then, how important it is to understand the soils on which you have to build; and how essential it is for an architect to have some acquaintance with geology. Remember this well, for the architects of the preceding generation have shown a contempt for these studies, and have relied on their contractors in many instances where that knowledge was required.

“We shall also take into consideration muddy low-lying soils, permeated by water, which cannot be dug into, because their consistency is little better than that of compact mud, and in which the deeper you dig the less resistance you meet. When these soils are not of a turfy description, contain little vegetable detritus, and always retain the same quantity of water, you can build upon them, for water is not compressible. Your building is then a kind of boat; the only question is, how to prevent the water from escaping, from receding under the weight of the structure as it does under that of a boat. When you plunge into a bath half full of water, the liquid rises along the brim proportionately to the volume of your body. But suppose that a board cut out so as exactly to fit the outline of your body, prevents the water from rising around you, you will not be able to sink into the water, and it will bear you on its surface. Well, then, the problem of building in a muddy soil consists in preventing the mud from rising around the house in proportion to the pressure. I must once more give you a sketch, showing the method of securing a successful result in this particular case. (Fig. 8.)

“Let us suppose we have been digging in ‘made ground’ A, _i.e._, ground in which we cannot build with security. At B we reach the virgin soil, but it is very moist—mud of old formation, permeated by water, and in which one sinks in walking. The deeper we go into it the softer we find it. A bar thrust down to the depth of two or three yards discovers no bottom, and the holes made in it are immediately filled with water. Piles driven in sink up to the head. Now, there can be no doubt that for an ordinary building it will not do to spend in foundations double what the building itself would cost. We must consider, therefore. In this case we shall dig a trench of about 1 foot 6 inches to 2 feet deep, to receive the walls forming the perimeter of the house, as drawn at E; then, in these trenches, and over the whole area of the building, we shall pour concrete, having a thickness of 2 feet to 2 feet 6 inches, between the trenches, as at F. We shall thus have formed a cover of homogeneous material, which will prevent the mud, G H, comprised within its edges, from rising. The weight of the made ground A will suffice to keep down the rest. On a plateau of this kind you will be able to build securely.

“You will, perhaps, ask me what ‘concrete’ is, and how it is made. You will learn this later on.”

Talking and making sketches, Paul and his cousin had reached the slope of the hill on which the house was to be built.

“The situation is good,” said Eugène. “We have an excellent calcareous soil, from which we shall even be able to get stone or rubble fit for building. Here, on the lower slopes, we have fairly clean sandy clay, with which we shall make brick. And there is the spring of fresh water coming from the wood, and passing out below the lowest of the limestone beds; we shall easily secure it, and lead it along the house, where it will be doubly useful, for it will give us water for the requirements of the household, and carry off in a drain all the house sewage and impurities, which we will discharge into that old excavation which I see on our left.

“However, we must examine before we proceed, for it seems to me that these beds have already been worked at some points. We should be very likely to meet with some of those carelessly-conducted quarryings which are too common in this neighbourhood.”

“How,” asked Paul, “can good building-stone be distinguished from that of inferior quality?”

“It is not always easy to distinguish it, and in this, as in many other branches of knowledge, experience must confirm theory. Among calcareous stones, which comprise, with certain sandstones, the materials that can be easily quarried and worked, some are hard, others soft; but the hardest are not always those which best resist the effects of time. Many limestones contain clay, and as this retains water, when frosts supervene, these clayey parts swell, and burst blocks whose substance is composed of carbonate of lime, and also of silica, in larger or smaller quantity. Limestones free from clay are those which best resist moisture, and are least liable to be damaged by frost. When, as here, we have beds laid bare by erosion, it is easy to distinguish the good from the defective ones. Thus, observe that large dark-looking mass, whose smooth bare edge has been covered with lichens for centuries; it is of an excellent quality, for lichens spread over a rock very slowly; and to enable them to attach themselves to this stone and give it that grey speckled appearance, the limestone must have resisted the decomposing action of the atmosphere. Now, look at that bed of nearly pure white, and which seems so sound. Well; it has this fair appearance only because at every frost it has lost its skin; its surface has been decomposed. Touch this rock, and you will observe a white dust remaining on your hands. It is so, is it not? The quality of this block is consequently bad; in fact, you see that below it the grass is covered with small calcareous exfoliations, whereas the turf under the grey block is quite free from dust. It is then very desirable for an architect, when he intends to build, to go and see the quarries, and observe how the beds that compose them stand when exposed to the air, a thing—I may tell you—our brethren rarely do.”

LESSON THE SECOND.

Paul was greatly pleased with the method adopted by his cousin for giving him the first notions of building. In the evening he presented as his day’s work a fair transcription of all that his teacher had explained to him on the ground. He even illustrated his text by some pretty good diagrams. The corrections were quickly made after dinner. But next day the incessant rain prevented them from going out, and Eugène decided that the second lecture should be given in the house. “We shall have illustrations enough before us; the _château_ itself will supply them. We will go through it from cellar to attic, and study its materials and methods of construction—to criticize them if they are bad, or to take note of them if they are good.” When teacher and pupil had gone down into the cellars, Eugène began by saying, “Look how damp this cellar wall on the side of the courtyard is; and see how the mortar in the joints of the stones has fallen, owing to two causes:—first, in building these walls, the precaution was not taken of cementing them on the outside, so as to make the water in the ground run down to the bottom; second, the mortar employed in the building was not made with hydraulic lime. There are two principal kinds of lime: fat or rich lime and hydraulic lime. The first is obtained by burning the compact limestones usually found at the top of the beds; it is called fat because when slaked it is glutinous and sticks to the tool with which it is mixed; this lime, on being immersed in water, swells and sends forth a dense vapour, as you may have observed, and mixed with sand is slow in setting. Employed above ground, mortars made with this lime become at length very hard, but retain more or less for a time a certain plasticity. These mortars, however, as they are slow in setting, are readily softened by water, and cannot then ever harden. Hydraulic limes, on the other hand (obtained by burning the lias limestones), when mixed with sand, soon become very hard, and set all the better for being in a damp place. Hence this lime is called _hydraulic_, because it is employed for all masonry-work under water. In default of lias limestones, artificial hydraulic limes are made, by grinding a certain proportion of clay with a limestone suitable for making ordinary lime. Hydraulic lime is tested by slacking—that is to say, mixing it with water; when it slakes with the production of very little vapour.

“It is with hydraulic lime that concretes, of which I spoke to you yesterday, are made. The mortar being prepared, a certain proportion of hard gravel, about the size of eggs, is mingled with it; the whole is well mixed and thrown into the excavations, where it is rammed with wooden rammers. If the lime is good and the concrete well made, it forms a veritable rock, similar to the conglomerates or pudding-stone of natural formation. As, when set, water penetrates with difficulty through these concretes, they prevent that percolation of subjacent water to which cellars made in wet grounds are liable.

“If the wall you see there had been built with mortar made with hydraulic lime, it would have been sound, and the mortar joints would have been as hard as the stone itself. You will easily understand that when the water has gradually softened and liquefied the mortar in the beds and joints at the base of a wall, the stones which compose it settle, and all the rest of the building suffers. That is why the front of the house, towards the court, presents a considerable number of cracks, that are filled in from time to time, but of course with no result in doing away with the cause of the mischief.

“You observe that the cellar wall which receives the arch of the vault is very thick, much thicker than is the wall of the ground floor. The latter is scarcely 2 feet thick, whereas this is full 3 feet. This additional thickness is given to the inside principally to receive the springing of the vault. A sketch will enable you to understand the reason of this arrangement. Let A (Fig. 9) be the thickness of the wall of a house on the ground floor—a thickness of 1 foot 8 inches if cellars are wanted beneath the ground floor; the floor line being at B and the outside ground line at C, it will be well first to indicate the floor line by a projection,—a greater thickness given to this wall on the outside, say of 2 inches. At A, then, the wall will have a thickness of 1 foot 10 inches. Your cellar arch being drawn at D, we must reserve a resting-place of at least 8 inches, to receive the first arch-stones of the spring of the vault; then it is well to give on the side next the ground a greater projection, to make a good footing for the plinth; this projection being 2 inches, we shall have at F a thickness of 2 feet and at G 2 feet 8 inches at least, as it will not do for the wall which rises to bear on the oblique beds of the vault, otherwise it would not have a solid footing, and would be weakened or reduced in thickness by this arch, which would penetrate it, as we see in the drawing I. But come here into this other cellar, which belongs to the oldest part of the _château_, and is built with good stones. The builder did not wish to lose space within, and as he built with worked stone he sought to economise material. What, then, did he do? (Fig. 10.) He gave his cellar wall only the thickness of that of the ground floor; at regular distances he put massive corbels 2 feet above the floor; upon these corbels he carried arches projecting 10 inches, and on these arches, which replace the extra thickness or counter-wall of which I spoke to you just now, he carried his vaulting arch. This perspective sketch will enable us readily to understand this method of construction. The upper wall thus leaves the vault perfectly free and rises plumb over its lower face.

“Is it all clear to you? Well, let us go and look at that little flight of steps which perhaps you have never attentively examined. It is 4 feet 3 inches wide, which was large enough to afford a passage to the _queues_ of wine. Observe (Fig. 11): the ramping vault is composed of as many arches, one above another, as there are steps; that is extremely well managed, solid and easily built. In fact, when the stone steps are laid, over above them is successively fixed the same wood centre which, of course, is raised at each step; and upon this centre an arch is built, which is quickly done, as the stones are worked ready. In this way the arches follow the section of the steps, and the centre being shifted—after each arch is keyed—to the next step commencing from the bottom, two men can turn five or six of these arches in one day, so that if there are twelve steps, this ramping vault may be built in two days. Look, I will show you how this construction should be denoted in perspective and geometrical section in your _résumé_ to-day—A and B.

“Let us go up to the ground floor. Look at the efflorescence resembling cotton wool on the interior of the walls: it is the saltpetre which forms inside the stone, and, through the humidity of the ground, crystallizes on the surface. This saltpetre affects the stone injuriously, ultimately eats it away, and throws off any painting that we might endeavour to use as a counteractive on the interior surface. Mastic cements are made to stop the effects of the saltpetre, but these means only delay its appearance for a short time without curing the evil, and this cement soon falls off in a crust. It is therefore necessary in building, especially in the country, to prevent the damp of the ground from rising up in the walls, and to stop it at the ground level. The interposition of a layer of pitch beneath the plinth has sometimes been tried, in order to prevent the absorption of damp by the stones—or what is called capillary attraction—but this method is very inefficient. The pitch oozes out under the pressure, as it does not harden sufficiently to bear that pressure, or it decomposes and combines with the lime. The best plan is to lay a course of slates in the mortar-bed between the first lower courses of the plinth. The slate effectually hinders that effect of capillary attraction, and the damp is unable to rise in the walls.

“Now observe this front wall in the court: it forms a protuberance at the floor level of the first story. We call that a bulging of the wall. Instead of preserving its vertical plane, as it should have done, it has bulged out; and why? Because it has been thrust out by a force acting from within outwards. What is that force? It might be an arch; but there is no arching on the ground floor. It can therefore be only the floor. It is not clear at first sight how a floor, which is a horizontal plane, can thrust; for to thrust, we must suppose the floor to expand in one direction, which cannot be. But see what happens. Give me your best attention.... Formerly, to compose a floor, large beams were laid from wall to wall, and upon these beams lighter pieces of timber, called joists; then on these was laid a bed of earth, gravel, or sand, and upon that a surface of mortar to receive the tiling. This made a very heavy mass. Now, as a piece of timber, even of considerable section, bends in time under its own weight—that is to say, from being straight becomes curved—its tendency to bend will be proportionally greater when it is weighted. The more it bends, the more powerful its thrust upon the inner surface of the walls in which it has its bearing. It is this pressure upon the interior surface that tends to thrust the wall outwards. But if, as in this case, in order to relieve the bearing of the beams, struts of wood have been put underneath (Fig. 12), this effect of thrust is all the more sensible because the arm of the lever is longer. You do not quite understand, I see. A sketch will make it clear to you. Let A be the section of the wall, or, if you will, its thickness. If the beam bends according to the line C D, there occurs a pressure at D, which produces a thrust at F and the rounding of the wall, as indicated by the dotted curves. Supposing even that in lieu of the strut E we have a stone corbel, the effect produced will be the same, though less forcible, unless the tail of the corbel reaches through the wall, as you see marked at I, and this tail K is weighted in such a manner that the weight neutralizes the pressure which the beam exerts at the end L. This has not been done here, where instead of the wood strut, a corbel was put. This corbel has but a middling hold in the wall, and the latter, formed of small stones not very well built, has not sufficient cohesion to resist the thrust exerted by the deflection of the beams. But why, you will ask me, has this effect been produced at the floor level of the first story and not above? Because, by the effect of the bulging we find here, the wall has inclined above towards the inside, and has thereby squeezed the second floor—its surfaces being placed, by their very inclination, perpendicularly to the curve line of the upper beams, as I indicate to you at M, exaggerating the effect for the purpose of making it clearer.

“You see that each detail merits attention, and that the builder ought to have a good reason for everything he does.

“In work of every kind we learn to avoid faults only by analysing and searching into their causes and ascertaining their effects. To become a good builder, therefore, it is not enough to familiarize one’s self with rules of construction, which cannot provide for all contingencies; we must see and observe much, and ascertain defective points in buildings that have been tested by time; just as physicians become able to determine what a good constitution is only by studying diseases and their causes. For the most part we appreciate what is good only through observing what is bad; if, in the absence of the bad, we are able to admit that there is such a thing as the good. An old proficient in architecture, who, when I was about your age, was so kind as to aid me with his advice, used often to say to me: ‘I can tell you, my dear fellow, what you must avoid in the art of building;—as to explaining to you in what the good and the beautiful consist, you must find out that yourself. If you are a born architect, you will know well enough how to discover it; if not, all that I could show you, all the examples I could place before you, would not give you talent.’ And he was right. The sight of the finest works in architecture may pervert the minds of students, if it’s not been explained to them how the authors of these works succeeded in making them beautiful by having avoided such or such faults.

“But you have enough to write out for to-day. Make a fair copy of these sketches opposite your text, and we will examine it this evening.”