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Therefore, where the mountains are not earthy but consist of soft stone, the force of the fire, passing through the fissures in the stone, sets it afire. The soft and delicate part is burned out, while the hard part is left. Consequently, while in Campania the burning of the earth makes ashes, in Tuscany the combustion of the stone makes carbuncular sand.
Both are excellent in walls, but one is better to use for buildings on land, the other for piers under salt water. The Tuscan stone is softer in quality than tufa but harder than earth, and being thoroughly kindled by the violent heat from below, the result is the production in some places of the kind of sand called carbuncular. Ancient quarries. A similar modern quarry. The top of the rock shows the original ground level.
The present ground level shows the depth to which the rock has been removed. I have now spoken of lime and sand, with their varieties and points of excellence. The stone in quarries is found to be of different and unlike qualities. In some it is soft: for example, in the environs of the city at the quarries of Grotta Rossa, Palla, Fidenae, and of the Alban hills; in others, it is medium, as at Tivoli, at Amiternum, or Mt. Soracte, and in quarries of this sort; in still others it is hard, as in lava quarries.
There are also numerous other kinds: for instance, in Campania, red and black tufas; in Umbria, Picenum, and Venetia, white tufa which can be cut with a toothed saw, like wood. All these soft kinds have the advantage that they can be easily worked as soon as they have been taken from the quarries. Under cover they play their part well; but in open and exposed situations the frost and rime make them crumble, and they go to pieces.
On the seacoast, too, the salt eats away and dissolves them, nor can they stand great heat either. But travertine and all stone of that class can stand injury whether from a heavy load laid upon it or from the weather; exposure to fire, however, it cannot bear, but splits and cracks to pieces at once. This is because in its natural composition there is but little moisture and not much of the earthy, but a great deal of air and of fire.
Therefore, it is not only without the earthy and watery elements, but when fire, expelling the air from it by the operation and force of heat, penetrates into its inmost parts and occupies the empty spaces of the fissures, there comes a great glow and the stone is made to burn as fiercely as do the particles of fire itself. There are also several quarries called Anician in the territory of Tarquinii, the stone being of the colour of peperino. The principal workshops lie round the lake of Bolsena and in the prefecture of Statonia.
Neither the season of frost nor exposure to fire can harm it, but it remains solid and lasts to a great age, because there is only a little air and fire in its natural composition, a moderate amount of moisture, and a great deal of the earthy. Hence its structure is of close texture and solid, and so it cannot be injured by the weather or by the force of fire. This may best be seen from monuments in the neighbourhood of the town of Ferento which are made of stone from these quarries.
Among them are large statues exceedingly well made, images of smaller size, and flowers and acanthus leaves gracefully carved. Old as these are, they look as fresh as if they were only just finished. Bronze workers, also, make moulds for the casting of bronze out of stone from these quarries, and find it very useful in bronze-founding.
If the quarries were only near Rome, all our buildings might well be constructed from the products of these workshops. But since, on account of the proximity of the stone-quarries of Grotta Rossa, Palla, and the others that are nearest to the city, necessity drives us to make use of their products, we must proceed as follows, if we wish our work to be finished without flaws.
Let the stone be taken from the quarry two years before building is to begin, and not in winter but in summer. Then let it lie exposed in an open place. Such stone as has been damaged by the two years of exposure should be used in the foundations. The rest, which remains unhurt, has passed the test of nature and will endure in those parts of the building which are above ground.
This precaution should be observed, not only with dimension stone, but also with the rubble which is to be used in walls. There are two styles of walls: "opus reticulatum," now used by everybody, and the ancient style called "opus incertum. Both kinds should be constructed of the smallest stones, so that the walls, being thoroughly puddled with the mortar, which is made of lime and sand, may hold together longer. Since the stones used are soft and porous, they are apt to suck the moisture out of the mortar and so to dry it up.
But when there is abundance of lime and sand, the wall, containing more moisture, will not soon lose its strength, for they will hold it together. But as soon as the moisture is sucked out of the mortar by the porous rubble, and the lime and sand separate and disunite, the rubble can no longer adhere to them and the wall will in time become a ruin.
This we may learn from several monuments in the environs of the city, which are built of marble or dimension stone, but on the inside packed with masonry between the outer walls. In the course of time, the mortar has lost its strength, which has been sucked out of it by the porousness of the rubble; and so the monuments are tumbling down and going to pieces, with their joints loosened by the settling of the material that bound them together.
He who wishes to avoid such a disaster should leave a cavity behind the facings, and on the inside build walls two feet thick, made of red dimension stone or burnt brick or lava in courses, and then bind them to the fronts by means of iron clamps and lead.
Consequently, the method of construction employed by the Greeks is not to be despised. They do not use a structure of soft rubble polished on the outside, but whenever they forsake dimension stone, they lay courses of lava or of some hard stone, and, as though building with brick, they bind the upright joints by interchanging the direction of the stones as they lie in the courses. Thus they attain to a perfection that will endure to eternity. These structures are of two kinds. One of them is called "isodomum," the other "pseudisodomum.
A wall is called isodomum when all the courses are of equal height; pseudisodomum, when the rows of courses do not match but run unequally. Both kinds are strong: first, because the rubble itself is of close texture and solid, unable to suck the moisture out of the mortar, but keeping it in its moist condition for a very long period; secondly, because the beds of the stones, being laid smooth and level to begin with, keep the mortar from falling, and, as they are bonded throughout the entire thickness of the wall, they hold together for a very long period.
In this the facings are finished, but the other stones left in their natural state and then laid with alternate bonding stones. But our workmen, in their hurry to finish, devote themselves only to the facings of the walls, setting them upright but filling the space between with a lot of broken stones and mortar thrown in anyhow.
This makes three different sections in the same structure; two consisting of facing and one of filling between them. Further, at intervals they lay single stones which run through the entire thickness of the wall. Moscioni Photo. One who in accordance with these notes will take pains in selecting his method of construction, may count upon having something that will last.
Hence, when arbitrators are chosen to set a valuation on party walls, they do not value them at what they cost to build, but look up the written contract in each case and then, after deducting from the cost one eightieth for each year that the wall has been standing, decide that the remainder is the sum to be paid.
They thus in effect pronounce that such walls cannot last more than eighty years. In the case of brick walls, however, no deduction is made provided that they are still standing plumb, but they are always valued at what they cost to build. Hence in some states we may see public buildings and private houses, as well as those of kings, built of brick: in Athens, for example, the part of the wall which faces Mt. Hymettus and Pentelicus; at Patras, the cellae of the temple of Jupiter and Hercules, which are brick, although on the outside the entablature and columns of the temple are of stone; in Italy, at Arezzo, an ancient wall excellently built; at Tralles, the house built for the kings of the dynasty of Attalus, which is now always granted to the man who holds the state priesthood.
In Sparta, paintings have been taken out of certain walls by cutting through the bricks, then have been placed in wooden frames, and so brought to the Comitium to adorn the aedileship of Varro and Murena. Then there is the house of Croesus which the people of Sardis have set apart as a place of repose for their fellow- citizens in the retirement of age,—a "Gerousia" for the guild of the elder men.
That king did not use brick from poverty; for he was choke-full of revenues, being ruler of all Caria. As for his skill and ingenuity as a builder, they may be seen from what follows.
He was born at Melassa, but recognizing the natural advantages of Halicarnassus as a fortress, and seeing that it was suitable as a trading centre and that it had a good harbour, he fixed his residence there.
The place had a curvature like that of the seats in a theatre. On the lowest tier, along the harbour, was built the forum. About halfway up the curving slope, at the point where the curved cross-aisle is in a theatre, a broad wide street was laid out, in the middle of which was built the Mausoleum, a work so remarkable that it is classed among the Seven Wonders of the World.
At the top of the hill, in the centre, is the fane of Mars, containing a colossal acrolithic statue by the famous hand of Leochares. That is, some think that this statue is by Leochares, others by Timotheus. At the extreme right of the summit is the fane of Venus and Mercury, close to the spring of Salmacis.
There is a mistaken idea that this spring infects those who drink of it with an unnatural lewdness. It will not be out of place to explain how this idea came to spread throughout the world from a mistake in the telling of the tale.
It cannot be that the water makes men effeminate and unchaste, as it is said to do; for the spring is of remarkable clearness and excellent in flavour. The fact is that when Melas and Arevanias came there from Argos and Troezen and founded a colony together, they drove out the Carians and Lelegans who were barbarians. Later, one of the colonists, to make money, set up a well-stocked shop, near the spring because the water was so good, and the way in which he carried it on attracted the barbarians.
So they began to come down, one at a time, and to meet with society, and thus they were brought back of their own accord, giving up their rough and savage ways for the delights of Greek customs. Hence this water acquired its peculiar reputation, not because it really induced unchastity, but because those barbarians were softened by the charm of civilization. But since I have been tempted into giving a description of this fortified place, it remains to finish my account of it.
Corresponding to the fane of Venus and the spring described above, which are on the right, we have on the extreme left the royal palace which king Mausolus built there in accordance with a plan all his own. Only the king himself could, in case of need, give orders from his own palace to the oarsmen and soldiers, without the knowledge of anybody else.
After the death of Mausolus, his wife Artemisia became queen, and the Rhodians, regarding it as an outrage that a woman should be ruler of the states of all Caria, fitted out a fleet and sallied forth to seize upon the kingdom. When news of this reached Artemisia, she gave orders that her fleet should be hidden away in that harbour with oarsmen and marines mustered and concealed, but that the rest of the citizens should take their places on the city wall.
After the Rhodians had landed at the larger harbour with their well-equipped fleet, she ordered the people on the wall to cheer them and to promise that they would deliver up the town. Then, when they had passed inside the wall, leaving their fleet empty, Artemisia suddenly made a canal which led to the sea, brought her fleet thus out of the smaller harbour, and so sailed into the larger. Disembarking her soldiers, she towed the empty fleet of the Rhodians out to sea.
So the Rhodians were surrounded without means of retreat, and were slain in the very forum. So Artemisia embarked her own soldiers and oarsmen in the ships of the Rhodians and set forth for Rhodes. The Rhodians, beholding their own ships approaching wreathed with laurel, supposed that their fellow-citizens were returning victorious, and admitted the enemy.
Then Artemisia, after taking Rhodes and killing its leading men, put up in the city of Rhodes a trophy of her victory, including two bronze statues, one representing the state of the Rhodians, the other herself.
Herself she fashioned in the act of branding the state of the Rhodians. Since such very powerful kings have not disdained walls built of brick, although with their revenues and from booty they might often have had them not only of masonry or dimension stone but even of marble, I think that one ought not to reject buildings made of brick-work, provided that they are properly "topped.
The laws of the state forbid that walls abutting on public property should be more than a foot and a half thick. The other walls are built of the same thickness in order to save space. Now brick walls, unless two or three bricks thick, cannot support more than one story; certainly not if they are only a foot and a half in thickness. But with the present importance of the city and the unlimited numbers of its population, it is necessary to increase the number of dwelling-places indefinitely.
Consequently, as the ground floors could not admit of so great a number living in the city, the nature of the case has made it necessary to find relief by making the buildings high. In these tall piles reared with piers of stone, walls of burnt brick, and partitions of rubble work, and provided with floor after floor, the upper stories can be partitioned off into rooms to very great advantage.
The accommodations within the city walls being thus multiplied as a result of the many floors high in the air, the Roman people easily find excellent places in which to live. It has now been explained how limitations of building space necessarily forbid the employment of brick walls within the city.
When it becomes necessary to use them outside the city, they should be constructed as follows in order to be perfect and durable. On the top of the wall lay a structure of burnt brick, about a foot and a half in height, under the tiles and projecting like a coping.
Thus the defects usual in these walls can be avoided. For when the tiles on the roof are broken or thrown down by the wind so that rainwater can leak through, this burnt brick coating will prevent the crude brick from being damaged, and the cornice-like projection will throw off the drops beyond the vertical face, and thus the walls, though of crude brick structure, will be preserved intact.
With regard to burnt brick, nobody can tell offhand whether it is of the best or unfit to use in a wall, because its strength can be tested only after it has been used on a roof and exposed to bad weather and time—then, if it is good it is accepted. If not made of good clay or if not baked sufficiently, it shows itself defective there when exposed to frosts and rime. Brick that will not stand exposure on roofs can never be strong enough to carry its load in a wall.
Hence the strongest burnt brick walls are those which are constructed out of old roofing tiles. As for "wattle and daub" I could wish that it had never been invented.
The more it saves in time and gains in space, the greater and the more general is the disaster that it may cause; for it is made to catch fire, like torches. It seems better, therefore, to spend on walls of burnt brick, and be at expense, than to save with "wattle and daub," and be in danger. For these swell with moisture as they are daubed, and then contract as they dry, and, by their shrinking, cause the solid stucco to split.
But since some are obliged to use it either to save time or money, or for partitions on an unsupported span, the proper method of construction is as follows. Give it a high foundation so that it may nowhere come in contact with the broken stone-work composing the floor; for if it is sunk in this, it rots in course of time, then settles and sags forward, and so breaks through the surface of the stucco covering. I have now explained to the best of my ability the subject of walls, and the preparation of the different kinds of material employed, with their advantages and disadvantages.
Next, following the guidance of Nature, I shall treat of the framework and the kinds of wood used in it, showing how they may be procured of a sort that will not give way as time goes on. Timber should be felled between early Autumn and the time when Favonius begins to blow.
For in Spring all trees become pregnant, and they are all employing their natural vigour in the production of leaves and of the fruits that return every year. The requirements of that season render them empty and swollen, and so they are weak and feeble because of their looseness of texture. This is also the case with women who have conceived. Their bodies are not considered perfectly healthy until the child is born; hence, pregnant slaves, when offered for sale, are not warranted sound, because the fetus as it grows within the body takes to itself as nourishment all the best qualities of the mother's food, and so the stronger it becomes as the full time for birth approaches, the less compact it allows that body to be from which it is produced.
After the birth of the child, what was heretofore taken to promote the growth of another creature is now set free by the delivery of the newborn, and the channels being now empty and open, the body will take it in by lapping up its juices, and thus becomes compact and returns to the natural strength which it had before.
On the same principle, with the ripening of the fruits in Autumn the leaves begin to wither and the trees, taking up their sap from the earth through the roots, recover themselves and are restored to their former solid texture. But the strong air of winter compresses and solidifies them during the time above mentioned. Consequently, if the timber is felled on the principle and at the time above mentioned, it will be felled at the proper season.
In felling a tree we should cut into the trunk of it to the very heart, and then leave it standing so that the sap may drain out drop by drop throughout the whole of it. In this way the useless liquid which is within will run out through the sapwood instead of having to die in a mass of decay, thus spoiling the quality of the timber.
Then and not till then, the tree being drained dry and the sap no longer dripping, let it be felled and it will be in the highest state of usefulness. That this is so may be seen in the case of fruit trees. But when the juices of trees have no means of escape, they clot and rot in them, making the trees hollow and good for nothing.
Therefore, if the draining process does not exhaust them while they are still alive, there is no doubt that, if the same principle is followed in felling them for timber, they will last a long time and be very useful in buildings.
Trees vary and are unlike one another in their qualities. Thus it is with the oak, elm, poplar, cypress, fir, and the others which are most suitable to use in buildings.
The oak, for instance, has not the efficacy of the fir, nor the cypress that of the elm. Nor in the case of other trees, is it natural that they should be alike; but the individual kinds are effective in building, some in one way, some in another, owing to the different properties of their elements.
To begin with fir: it contains a great deal of air and fire with very little moisture and the earthy, so that, as its natural properties are of the lighter class, it is not heavy. Hence, its consistence being naturally stiff, it does not easily bend under the load, and keeps its straightness when used in the framework. But it contains so much heat that it generates and encourages decay, which spoils it; and it also kindles fire quickly because of the air in its body, which is so open that it takes in fire and so gives out a great flame.
The part which is nearest to the earth before the tree is cut down takes up moisture through the roots from the immediate neighbourhood and hence is without knots and is "clear. The lowest part, after the tree is cut down and the sapwood of the same thrown away, is split up into four pieces and prepared for joiner's work, and so is called "clearstock.
Oak, on the other hand, having enough and to spare of the earthy among its elements, and containing but little moisture, air, and fire, lasts for an unlimited period when buried in underground structures. It follows that when exposed to moisture, as its texture is not loose and porous, it cannot take in liquid on account of its compactness, but, withdrawing from the moisture, it resists it and warps, thus making cracks in the structures in which it is used.
The winter oak, being composed of a moderate amount of all the elements, is very useful in buildings, but when in a moist place, it takes in water to its centre through its pores, its air and fire being expelled by the influence of the moisture, and so it rots.
The Turkey oak and the beech, both containing a mixture of moisture, fire, and the earthy, with a great deal of air, through this loose texture take in moisture to their centre and soon decay. White and black poplar, as well as willow, linden, and the agnus castus, containing an abundance of fire and air, a moderate amount of moisture, and only a small amount of the earthy, are composed of a mixture which is proportionately rather light, and so they are of great service from their stiffness.
The Architecture of British Bridges. During the Industrial Revolution, Britain was at the forefront of bridge innovation. Pioneering designers such as George and Robert Stephenson, Thomas Telford and Isambard Kingdom Brunel created Britain's rich bridge heritage that features many world firsts and we can learn much from their ground-breaking designs.
Written by an experienced bridge. How to Read Bridges.
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