Vitruvio - De Architectura - Book I


1. Whilst, O CÊsar, your god-like mind and genius were engaged in acquiring the dominion of the world, your enemies having been all subdued by your unconquerable valour; whilst the citizens were extolling your victories, and the conquered nations were awaiting your nod; whilst the Roman senate and people, freed from alarm, were enjoying the benefit of your opinions and counsel for their governance; I did not presume, at so unfit a period, to trouble you, thus engaged, with my writings on Architecture, lest I should have incurred your displeasure.

2. When, however, I found that your attention, not exclusively devoted to state affairs, was bestowed on the state of the public buildings, so that the republic was not more indebted to you for its extended empire, in the addition of so many provinces, than for your numerous public buildings by which its grandeur is amply manifested, I considered it right that no time should be lost in laying these precepts before you. My reverence for the memory of your virtuous father, to whom I was well known, and from whom, now a participator in council with the gods, the empire descended to you, has been the cause of your good will towards me. Hence, together with M. Aurelius, P. Numisius, and Cn. Cornelius, I have been appointed to, and receive the emoluments arising from the care of, the various engines of war which you assigned to me on the recommendation of your sister.

3. As, through your kindness, I have been thus placed beyond the reach of poverty, I think it right to address this treatise to you; and I feel the more induced to do so from your having built, and being still engaged in the erection of, many edifices. It is proper to deliver down to posterity, as a memorial, some account of these your magnificent works. I have therefore given such definite directions for the conduct of works, that those already executed, as well as those hereafter to be constructed, may be by you well known and understood. In the following pages I have developed all the principles of the art.

Chapter 1

1.Architecture is a science arising out of many other sciences, and adorned with much and varied learning; by the help of which a judgment is formed of those works which are the result of other arts. Practice and theory are its parents. Practice is the frequent and continued contemplation of the mode of executing any given work, or of the mere operation of the hands, for the conversion of the material in the best and readiest way. Theory is the result of that reasoning which demonstrates and explains that the material wrought has been so converted as to answer the end proposed.

2.Wherefore the mere practical architect is not able to assign sufficient reasons for the forms he adopts; and the theoretic architect also fails, grasping the shadow instead of the substance. He who is theoretic as well as practical, is therefore doubly armed; able not only to prove the propriety of his design, but equally so to carry it into execution.

3.In architecture, as in other arts, two considerations must be constantly kept in view; namely, the intention, and the matter used to express that intention: but the intention is founded on a conviction that the matter wrought will fully suit the purpose; he, therefore, who is not familiar with both branches of the art, has no pretension to the title of the architect. An architect should be ingenious, and apt in the acquisition of knowledge. Deficient in either of these qualities, he cannot be a perfect master. He should be a good writer, a skilful draftsman, versed in geometry and optics, expert at figures, acquainted with history, informed on the principles of natural and moral philosophy, somewhat of a musician, not ignorant of the sciences both of law and physic, nor of the motions, laws, and relations to each other, of the heavenly bodies.

4.By means of the first named acquirement, he is to commit to writing his observations and experience, in order to assist his memory. Drawing is employed in representing the forms of his designs. Geometry affords much aid to the architect: to it he owes the use of the right line and circle, the level and the square; whereby his delineations of buildings on plane surfaces are greatly facilitated. The science of optics enables him to introduce with judgment the requisite quantity of light, according to the aspect. Arithmetic estimates the cost, and aids in the measurement of the works; this, assisted by the laws of geometry, determines those abstruse questions, wherein the different proportions of some parts to others are involved.

5. Unless acquainted with history, he will be unable to account for the use of many ornaments which he may have occasion to introduce. For instance; should any one wish for information on the origin of those draped matronal figures crowned with a mutulus and cornice, called Caryatides, he will explain it by the following history. Carya, a city of Peloponnesus, joined the Persians in their war against the Greeks. These in return for the treachery, after having freed themselves by a most glorious victory from the intended Persian yoke, unanimously resolved to levy war against the Caryans. Carya was, in consequence, taken and destroyed, its male population extinguished, and its matrons carried into slavery. That these circumstances might be better remembered, and the nature of the triumph perpetuated, the victors represented them draped, and apparently suffering under the burthen with which they were loaded, to expiate the crime of their native city. Thus, in their edifices, did the antient architects, by the use of these statues, hand down to posterity a memorial of the crime of the Caryans.

6. Again; a small number of Lacedmonians, under the command of Pausanias, the son of Cleombrotus, overthrew the prodigious army of the Persians at the battle of Platea. After a triumphal exhibition of the spoil and booty, the proceeds of the valour and devotion of the victors were applied by the government in the erection of the Persian portico; and, as an appropriate monument of the victory, and a trophy for the admiration of posterity, its roof was supported by statues of the barbarians, in their magnificent costume; indicating, at the same time the merited contempt due to their haughty projects, intimidating their enemies by fear of their courage, and acting as a stimulus to their fellow countrymen to be always in readiness for the defence of the nation. This is the origin of the Persian order for the support of an entablature; an invention which has enriched many a design with the singular variety it exhibits. Many other matters of history have a connexion with architecture, and prove the necessity of its professors being well versed in it.

7. Moral philosophy will teach the architect to be above meanness in his dealings, and to avoid arrogance: it will make him just, compliant and faithful to his employer; and what is of the highest importance, it will prevent avarice gaining an ascendancy over him: for he should not be occupied with the thoughts of filling his coffers, nor with the desire of grasping every thing in the shape of gain, but, by the gravity of his manners, and a good character, should be careful to preserve his dignity. In these respects we see the importance of moral philosophy; for such are her precepts. That branch of philosophy which the Greeks call fusiologiva, or the doctrine of physics, is necessary to him in the solution of various problems; as for instance, in the conduct, whose natural force, in its meandering and expansion over flat countries, is often such as to require restraints, which none know how to apply, but those who are acquainted with the laws of nature: nor, indeed, unless grounded in the first principles of physic, can he study with profit the works of Ctesibius, Archimedes, and many other authors who have written on the subject. 

8. Music assists him in the use of harmonic and mathematical proportion. It is, moreover, absolutely necessary in adjusting the force of the balist, catapult, and scorpions, in whose frames are holes for the passage of the homotona, which are strained by gut-ropes attached to windlasses worked by hand-spikes. Unless these ropes are equally extended, which only a nice ear can discover by their sound when struck, the bent arms of the engine do not give an equal impetus when disengaged, and the strings, therefore, not being in equal states of tension, prevent the direct flight of the weapon.

9. So the vessels called hjceia by the Greeks, which are placed in certain recesses under the seats of theatres, are fixed and arranged with a due regard to the laws of harmony and physics, their tones being fourths, fifths, and octaves; so that when the voice of the actor is in unison with the pitch of these instruments, its power is increased and mellowed by impinging thereon. He would, moreover, be at a loss in constructing hydraulic and other engines, if ignorant of music.

10. Skill in physic enables him to ascertain the salubrity of different tracts of country, and to determine the variation of climates, which the Greeks call klivmata: for the air and water of different situations, being matters of the highest importance, no building will be healthy without attention to those points. Law should be an object of his study, especially those parts of it which relate to party-walls, to the free course and discharge of the eaveswaters, the regulations of sesspools and sewage, and those relating to window lights. The laws of sewage require his particular attention, that he may prevent his employers being involved in law-suits when the building is finished. Contracts, also, for the execution of the works, should be drawn with care and precision: because, when without legal flaws, neither party will be able to take advantage of the other. Astronomy instructs him in the points of the heavens, the laws of the celestial bodies, the equinoxes, solstices, and courses of the stars; all of which should be well understood, in the construction and proportions of clocks.

11. Since, therefore, this art is founded upon and adorned with so many different sciences, I am of opinion that those who have not, from their early youth, gradually climbed up to the summit, cannot, without presumption, call themselves masters of it.

12. Perhaps, to the uninformed, it may appear unaccountable that a man should be able to retain in his memory such a variety of learning; but the close alliance with each other, of the different branches of science, will explain the difficulty. For as a body is composed of various concordant members, so does the whole circle of learning consist in one harmonious system. Wherefore those, who from an early age are initiated in the different branches of learning, have a facility in acquiring some knowledge of all, from their common connexion with each other. On this account Pythius, one of the antients, architect of the noble temple of Minerva at Priene, says, in his commentaries, that an architect should have that perfect knowledge of each art and science which is not even acquired by the professors of any one in particular, who have had every opportunity of improving themselves in it. This, however, cannot be necessary; 13.for how can it be expected that an architect should equal Aristarchus as a grammarian, yet should he not be ignorant of grammar. In music, though it be evident he need not equal Aristoxenus, yet he should know something of it. Though he need not excel, as Apelles, in painting, nor as Myron or Polycletus, in sculpture, yet he should have attained some proficiency in these arts. So, in the science of medicine, it is not required that he should equal Hippocrates. Thus also, in other sciences, it is not important that pre-eminence in each be gained, but he must not, however, be ignorant of the general principles of each. For in such a variety of matters, it cannot be supposed that the same person can arrive at excellence in each, since to be aware of their several niceties and bearings, cannot fall within his power. 

14. We see how few of those who profess a particular art arrive at perfection in it, so as to distinguish themselves: hence, if but few of those practising an individual art, obtain lasting fame, how should the architect, who is required to have a knowledge of so many, be deficient in none of them, and even excel those who have professed any one exclusively.

15. Wherefore Pythius seems to have been in error, forgetting that art consists in practice and theory. Theory is common to, and may be known by all, but the result of practice occurs to the artist in his own art only. The physician and musician are each obliged to have some regard to the beating of the pulses, and the motion of the feet, but who would apply to the latter to heal a wound or cure a malady? so, without the aid of the former, the musician affects the ears of his audience by modulations upon his instrument.

16. The astronomer and musician delight in similar proportions, for the positions of the stars, which are quartile and trine, answer to a fourth and fifth in harmony. The same analogy holds in that branch of geometry which the Greeks call lovgoV ojptiko`V: indeed, throughout the whole range of art, there are many incidents common to all. Practice alone can lead to excellence in any one: that architect, therefore, is sufficiently educated, whose general knowledge enables him to give his opinion on any branch when required to do so.

17. Those unto whom nature has been so bountiful that they are at once geometricians, astronomers, musicians, and skilled in many other arts, go beyond what is required of the architect, and may be properly called mathematicians, in the extended sense of that word. Men so gifted, discriminate acutely, and are rarely met with. Such, however, was Aristarchus of Samos, Philolaus and Archytas of Tarentum, Apollonius of Perga, Eratosthenes of Cyrene, Archimedes and Scopinas of Syracuse: each of whom wrote on all the sciences.

18. Since, therefore, few men are thus gifted, and yet it is required of the architect to be generally well informed, and it is manifest he cannot hope to excel in each art, I beseech you, O Csar, and those who read this my work, to pardon and overlook grammatical errors; for I write neither as an accomplished philosopher, an eloquent rhetorician, nor an expert grammarian, but as an architect: in respect, however, of my art and its principles, I will lay down rules which may serve as an authority to those who build, as well as to those who are already somewhat acquainted with the science.

Chapter 2

1. Architecture depends on fitness (ordinatio) and arrangement (dispositio), the former being called tavxiV, in Greek, and the latter diavqesiV; it also depends on proportion, uniformity, consistency, and economy, which the Greeks call oijkonomiva.

2. Fitness is the adjustment of size of the several parts to their several uses, and required due regard to the general proportions of the fabric: it arises out of dimension (quantitas), which the Greeks call posovthV. Dimension regulated the general scale of the work, so that the parts may all tell and be effective. Arrangement is the disposition in their just and proper places of all the parts of the building, and the pleasing effect of the same; keeping in view its appropriate character. It is divisible into three heads, which, considered together, constitute design: these, by the Greeks, are named ijdevai: they are called ichnography, orthography, and scenography. The first is the representation on a plane of the ground-plan of the work, drawn by rule and compasses. The second is the elevation of the front, slightly shadowed, and shewing the forms of the intended building. The last exhibits the front and a receding side properly shadowed, the lines being drawn to their proper vanishing points. These three are the result of thought and invention. Thought is an effort of the mind, ever incited by the pleasure attendant on success in compassing an object. Invention is the effect of this effort; which throws a new light on things the most recondite, and produces them to answer the intended purpose. These are the ends of arrangement.

3. Proportion is that agreeable harmony between the several parts of a building, which is the result of a just and regular agreement of them with each other; the height to the width, this to the length, and each of these to the whole.

4. Uniformity is the parity of the parts to one another; each corresponding with its opposite, as in the human figure. The arms, feet, hands, fingers, are similar to, and symmetrical with, one another; so should the respective parts of a building correspond. In the balista, by the size of the hole which the Greeks call perivtrhton; in ships, by the space between the thowls, which space in Greek is called diphcaikh`, we have a measure, by the knowledge of which the whole of the construction of a vessel may be developed.

5. Consistency is found in that work whose whole and detail are suitable to the occasion. It arises from circumstance, custom, and nature. From circumstance, which the Greeks call qematismo`V, when temples are built, hypthral and uninclosed, to Jupiter, Thunderer, Coelus, the Sun and Moon; because these divinities are continually known to us by their presence night and day, and throughout all space. For a similar reason, temples of the Doric order are erected to Minerva, Mars, and Hercules; on account of whose valour, their temples should be of masculine proportions, and without delicate ornament. The character of the Corinthian order seems more appropriate to Venus, Flora, Proserpine, and Nymphs of Fountains; because its slenderness, elegance and richness, and its ornamental leaves surmounted by volutes, seem to bear an analogy to their dispositions. A medium between these two is chosen for temples to Juno, Diana, Bacchus, and other similar deities, which should be of the Ionic order, tempered between the severity of the Doric and the slenderness and delicacy of the Corinthian order.

6. In respect of custom, consistency is preserved when the vestibules of magnificent edifices are conveniently contrived and richly finished: for those buildings cannot be said to be consistent, to whose splendid interiors you pass through poor and mean entrances. So also, if dentilled cornices are used in the Doric order, or triglyphs applied above the voluted Ionic, thus transferring parts to one order which properly belong to another, the eye will be offended, because custom otherwise applies these peculiarities.

7. Natural consistency arises from the choice of such situations for temples as possess the advantages of salubrious air and water; more especially in the case of temples erected to sculapius, to the Goddess of Health, and such other divinities as possess the power of curing diseases. For thus the sick, changing the unwholesome air and water to which they have been accustomed for those that are healthy, sooner convalesce; and a reliance upon the divinity will be therefore increased by proper choice of situation. Natural consistency also requires that chambers should be lighted from the east; baths and winter apartments from the south-west; picture and other galleries which require a steady light, from the north, because from that quarter the light is not sometimes brilliant and at other times obscured, but is nearly the same throughout the day.

8. Economy consists in a due and proper application of the means afforded according to the ability of the employer and the situation chosen; care being taken that the expenditure is prudently conducted. In this respect the architect is to avoid the use of materials which are not easily procured and prepared on the spot. For it cannot be expected that good pit-sand, stone, fir of either sort, or marble, can be procured every where in plenty, but they must, in some instances, be brought from a distance, with much trouble and at great expense. In such cases, river or sea sand may be substituted for pit-sand; cypress, poplar, elm, and pine, for the different sorts of fir; and the like of the rest, according to circumstances.

9. The other branch of economy consists in suiting the building to the use which is to be made of it, the money to be expended, and the elegance appropriate thereto; because, as one or other of these circumstances prevails, the design should be varied. That which would answer very well as a town house, would ill suit as a country house, in which store-rooms must be provided for the produce of the farm. So the houses of men of business must be differently designed from those which are built for men of taste. Mansions for men of consequence in the governement must be adapted to their particular habits. In short, economy must ever depend on the circumstances of the case.

Chapter 3

1. Architecture consists of three branches; namely, building, dialling, and mechanics. Building is divided into two parts. The first regulates the general plan of the walls of a city and its public buildings; the other relates to private buildings. Public buildings are for three purposes; defence, religion, and the security of the public. Buildings for defence are those walls, towers, and gates of a town, necessary for the continual shelter of its inhabitants against the attacks of an enemy. Those for the purposes of religion are the fanes and temples of the immortal gods. Those for public convenience are gates, fora or squares for market-places, baths, theatres, walks, and the like; which, being for public use, are placed in public situations, and should be arranged to as best to meet the convenience of the public.

2. All these should possess strength, utility, and beauty. Strength arises from carrying down the foundations to a good solid bottom, and from making a proper choice of materials without parsimony. Utility arises from a judicious distribution of the parts, so that their purposes be duly answered, and that each have its proper situation. Beauty is produced by the pleasing appearance and good taste of the whole, and by the dimensions of all the parts being duly proportioned to each other.

Chapter 4

1. In setting out the walls of a city the choice of a healthy situation is of the first importance: it should be on high ground, neither subject to fogs nor rains; its aspects should be neither violently of the nor intensely cold, but temperate in both respects. The neighbourhood of a marshy place must be avoided; for in such a site the morning air, uniting with the fogs that rise in the neighbourhood, will reach the city with the rising sun; and these fogs and mists, charged with the exhalation of the fenny animals, will diffuse an unwholesome effluvia over the bodies of the inhabitants, and render the place pestilent. A city on the sea side, exposed to the south or west, will be insalubrious; for in summer mornings, a city thus placed would be hot, at noon it would be scorched. A city, also, with a western aspect, would even at sunrise be warm, at noon hot, and in the evening of a burning temperature.

2. Hence the constitutions of the inhabitants of such places, from such continual and excessive changes of the air, would be much vitiated. This effect is likewise produced on inanimate bodies: nobody would think of lighting his wine-cellar from the south or the west, but from the north, an aspect not liable to these violent changes. In granaries whose aspects are south of the east or west, the stores are soon ruined; and provisions, as well as fruits, cannot be long preserved unless kept in apartments whose aspects are north of the east or west. 

3. For heat, which acts as an alterative, by drying up the natural moisture of any body, destroys and rots those substances on which it acts. Iron, for instance, naturally of a hard texture, becomes so soft when heated in a forge as to be easily wrought into any form; but if, when heated, it is suddenly immersed in cold water, it immediately regains its original quality.

4. Thus, not only in unwholesome, but also in salubrious districts, the summer heats produce languor and relaxation of body; and in winter, even the most pestilential situations become wholesome, inasmuch as the cold strengthens and restores the constitution of the inhabitants. Hence, those who change a cold for a hot climate, rarely escape sickness, but are soon carried off; whereas, on the other hand, those who pass from a hot to a cold climate, far from being injured by the change, are thereby generally strengthened.

5. Much care, then, should be taken so to set out the walls of a city, that it may not be obnoxious to the pestilential blasts of the hot winds. For as, according to those principles which the Greeks call stoiceia, all bodies are compounded of fire, water, earth, and air, by whose union and varying proportions the different qualities of animals are engendered;

6. so, in those bodies wherein fire predominates, their temperament is destroyed, and their strength dissipated. Such is the case in exposure to certain aspects of the heavens whence the heat insinuates itself through the pores in a greater degree than the temperature of the system will bear. Bodies which contain a greater proportion of water than is necessary to balance the other elements, are speedily corrupted, and lose their virtues and properties. Hence bodies are much injured by damp winds and atmosphere. Lastly, the elements of earth and air being increased or diminished more than is consistent with the temperature of any given body, will have a tendency to destroy its equilibrium; the earthy elements by repletion, the arial by the weight of the atmosphere.

7. If any one doubt this, let him study the different natures of birds, fishes, and animals of the land, and he will easily perceive the truth of these principles, from the variety existing among them. For there is one flesh of birds, another of fishes, and another, very different, of land animals. Birds have a small proportion of earth and water in their nature, a moderate quantity of heat, and a considerable portion of air; whence, being light by nature, from their component elements, they more easily raise themselves in the air. Fishes, by nature adapted to the watery element, are compounded of but a moderate degree of heat, a considerable proportion of air and earth, and a very small portion of water, the element in which they live; and hence, easier exist in it. Wherefore, when removed from it, they soon die. Terrestrial animals, being constituted with much air, heat, and water, and but little earth, cannot live in the water, on account of the quantity of that element naturally preponderating in their composition.

8. Since, then, we are thus constantly thus reminded, by our senses, that the bodies of animals are so constituted, and we have mentioned that they suffer and die from the want or superabundance of any one element not suitable to their temperament, surely much circumspection should be used in the choice of a temperate and healthy site for a city.

9. The precepts of the ancients, in this respect, should ever be observed. They always, after sacrifice, carefully inspected the livers of those animals fed on that spot whereon the city was to be built, or whereon a stative encampment was intended. If the livers were diseased and livid, they tried others, in order to ascertain whether accident or disease was the cause of the imperfection; but if the greater part of the experiments proved, by the sound and healthy appearance of the livers, that the water and food of the spot were wholesome, they selected it for the garrison. If the reverse, they inferred, as in the case of cattle, so in that of the human body, the water and food of such a place would become pestiferous; and they therefore abandoned it, in search of another, valuing health above all other considerations.

10. That the salubrity of a tract of land is discovered by the pastures or food which it furnishes, is sufficiently clear, from certain qualities of the lands in Crete, situate in the vicinity of the river Pothereus, which lie between the two states of Gnosus and Gortyna. There are pasturages on each side of this river: the cattle, however, pastured on the Gnossian side, when opened, are found with their spleens perfect; whilst those on the opposite side, nearer to Gortyna, retain no appearance of a spleen. Physicians, in their endeavours to account for this singular circumstance, discovered a species of herb eaten by the cattle, whose property was that of diminishing the spleen. Hence arose the use of the herb which the Cretans call a[splhnoV, as a cure for those affected with enlarged spleen.

11. When, therefore, a city is built in a marshy situation near the sea-coast, with a northern, north-eastern, or eastern aspect, on a marsh whose level is higher than the shore of the sea, the site is not altogether improper; for by means of sewers the waters may be discharged into the sea: and at those times, when violently agitated by storms, the sea swells and runs up the sewers, it mixes with the water of the marsh, and prevents the generation of marshy insects; it also soon destroys such as are passing from the higher level, by the saltness of its water to which they are unaccustomed. An instance of this kind occurs in the Gallic marshes about Altinum, Ravenna, and Aquileia, and other places in Cisalpine Gaul, near marshes which, for the reasons above named, are remarkably healthy.

12. When the marshes are stagnant, and have no drainage by means of rivers or drains, as is the case with the Pontine marshes, they become putrid, and emit vapours of a heavy and pestilent nature. Thus the old city of Salapia, in Apulia, built, as some say, by Diomedes on his return from Troy, or, as others write, by Elphias the Rhodian, was so placed that the inhabitants were continually out of health. At length they applied to Marcus Hostilius, and publicly petitioned him, and obtained his consent, to be allowed to seek and select a more wholesome spot to which the city might be removed. Without delay, and with much judgment, he bought an estate on a healthy spot close to the sea, and requested the Roman senate and people to permit the removal of the city. He then set out the walls, and assigned a portion of the soil to each citizen at a moderate valuation. After which, opening a communication between the lake and the sea, he converted the former into an excellent harbour for the city. Thus the Salapians now inhabit a healthy situation, four miles from their ancient city.

Chapter 5

1. When we are satisfied with the spot fixed on for the site of the city, as well as in respect of the goodness of the air as of the abundant supply of provisions for the support of the population, the communications by good roads, and river or sea navigation for the transport of merchandise, we should take into consideration the method of constructing the walls and towers of the city. Their foundations should be carried down to a solid bottom, if such can be found, and should be built thereon of such thickness as may be necessary for the proper support of that part of the wall which stands above the natural level of the ground. They should be of the soundest workmanship and materials, and of greater thickness than the walls above.

2. From the exterior face of the wall towers must be projected, from which an approaching enemy may be annoyed by weapons, from the embrasures of those towers, right and left. An easy approach to the walls must be provided against: indeed they should be surrounded by uneven ground, and the roads leading to the gates should be winding and turn to the left from the gates. 

By this arrangement, the right sides of the attacking troops, which are not covered by their shields, will be open to the weapons of the besieged. The plan of a city should not be square, nor formed with acute angles, but polygonal; so that the motions of the enemy may be open to observation. A city whose plan is acute-angled, is with difficulty defended; for such a form protects the attacker more than the attacked.

3. The thickness of the walls should be sufficient for two armed men to pass each other with ease. The walls ought to be tied, from front to rear, with many pieces of charred olive wood; by which means the two faces, thus connected, will endure for ages. The advantage of the use of olive is, that it is neither affected by weather, by rot, or by age. Buried in the earth, or immersed in water, it lasts unimpaired: and for this reason, not only walls, but foundations, and such walls as are of extraordinary thickness, tied together therewith, are exceedingly lasting.

4. The distance between each tower should not exceed an arrows flight; so that if, at any point between them, an attack be made, the besiegers may be repulsed by the scorpions and other missile engines stationed on the towers right and left of the point in question. The walls will be intercepted by the lower parts of the towers where they occur, leaving an interval equal to the width of the tower; which space the tower will consequently occupy: but the communication across the void inside the tower, must be of wood, not at all fastened with iron: so that, if the enemy obtain possession of any part of the walls, the wooden communication may be promptly cut away by the defenders, and thus prevent the enemy from penetrating to the other parts of the walls without the danger of precipitating themselves into the vacant hollows of the towers.

5. The towers should be made either round or polygonal. A square is a bad form, on account of its being easily fractured at the quoins by the battering-ram; whereas the circular tower has this advantage, that, when battered, the pieces of masonry whereof it is composed being cuneiform, they cannot be driven in towards their centre without displacing the whole mass. Nothing tends more to the security of walls and towers, than backing them with walls or terraces: it counteracts the effects of rams as well as of undermining.

6. It is not, however, always necessary to construct them in this manner, except in places where the besiegers might gain high ground very near the walls, from which, over level ground, an assault could be made. In the construction of ramparts, very wide and deep trenches are first to be excavated; the bottom of which must be still further dug out, for receiving the foundation of the wall. This must be of sufficient thickness to resist the pressure of the earth against it.

7. Then, according to the space requisite for drawing up the cohorts in military order on the rampart, another wall is to be built within the former, towards the city. The outer and inner walls are then to be connected by cross walls, disposed on the plan after the manner of the teeth of a comb or of a saw, so as to divide the pressure of the filling in earth into many and less forces, and thus prevent the walls from being thrust out.

8. I do not think it requisite to dilate on the materials whereof the wall should be composed; because those which are most desirable, cannot, from the situation of a place, be always procured. We must, therefore, use what are found on the spot; such as square stones, flint, rubble stones, burnt or unburnt bricks; for every place is not provided, as is Babylon, with such a substitute for lime and sand as burnt bricks and liquid bitumen; yet there is scarcely any spot which does not furnish materials whereof a durable wall may not be built. 

Chapter 6

1. Their circuit being completed, it behoves us to consider the manner of disposing of the area of the space enclosed within the walls, and the proper directions and aspects of the streets and lanes. They should be so planned as to exclude the winds: these, if cold, are unpleasant; if hot, are hurtful; if damp, destructive. A fault in this respect must be therefore avoided, and care taken to prevent that which occurs in so many cities. For instance; in the island of Lesbos, the town of Mytilene is magnificently and elegantly designed, and well built, but imprudently placed. When the south wind prevails in it, the inhabitants fall sick; the north-west wind affects them with coughs; and the north wind restores them to health: but the intensity of the cold therein is so great, that no one can stand about in the streets and lanes.

2. Wind is a floating wave of air, whose undulation continually varies. It is generated by the action of heat upon moisture, the rarefaction thereby produced creating a continued rush of wind. That such is the case, may be satisfactorily proved by observations on brazen olipyl, which clearly shew that an attentive examination of human inventions often leads to a knowledge of the general laws of nature. olipylare hollow brazen vessels, which have an opening or mouth of small size, by means of which they can be filled with water. Previous to the water being heated over the fire, but little wind is emitted, as soon, however, as the water begins to boil, a violent wind issues forth. Thus a simple experiment enables us to ascertain and determine the causes and effects of the great operations of the heavens and the winds.

3. In a place sheltered from the winds, those who are in health preserve it, those who are ill soon convalesce, though in other, even healthy places, they would require different treatment, and this entirely on account of their shelter from the winds. The disorders difficult to cure in exposed situations are colds, the gout, coughs, phthisis, pleurisy, spitting of blood, and those diseases which are treated by replenishment instead of exhaustion of the natural forces.
Such disorders are cured with difficulty. First, because they are the effect of cold; secondly, because the strength of the patient being greatly diminished by the disorder, the air agitated by the action of the winds becomes poor and exhausts the bodys moisture, tending to make it low and feeble; whereas, that air which from its soft and thick nature is not liable to great agitation, nourishes and refreshes its strength.

4. According to some, there are but four winds, namely, Solanus, the east wind, Auster, the south wind, Favonius, the west wind, and Septentrio, the north wind. But those who are more curious in these matters reckon eight winds; among such was Andronicus Cyrrhestes, who, to exemplify the theory, built at Athens
an octagonal marble tower, on each side of which was sculptured a figure representing the wind blowing from the quarter opposite thereto. On the top of the roof of this tower a brazen Triton with a rod in its right hand moved on a pivot, and pointed to the figure of the quarter in which the wind lay.

5. The other winds not above named are Eurus, the south-east wind, Africus, the south-west wind, Caurus, by many called Corus, the north-west wind, and Aquilo the north-east wind. Thus are expressed the number and names of the winds and the points whence they blow. To find and lay down their situation we proceed as follows:

6. let a marble slab be fixed level in the centre of the space enclosed by the walls, or let the ground be smoothed and levelled, so that the slab may not be necessary. In the centre of this plane, for the purpose of marking the shadow correctly, a brazen gnomon must be erected. The Greeks call this gnomon skiaqhvraV. The shadow cast by the gnomon is to be marked about the fifth ante-meridional hour, and the extreme point of the shadow accurately determined. From the central point of the space whereon the gnomon stands, as a centre, with a distance equal to the length of the shadow just observed, describe a circle. After the sun has passed the meridian, watch the shadow which the gnomon continues to cast till the moment when its extremity again touches the circle which has been described.

7. From the two points thus obtained in the circumference of the circle describe two arcs intersecting each other, and through their intersection and the centre of the circle first described draw a line to its extremity: this line will indicate the north and south points. One-sixteenth part of the circumference of the whole circle is to be set out to the right and left of the north and south points, and drawing lines from the points thus obtained to the centre of the circle, we have one-eighth part of the circumference for the region of the north, and another eighth part for the region of the south. Divide the remainders of the circumference on each side into three equal parts, and the divisions or regions of the eight winds will be then obtained: then let the directions of the streets and lanes be determined by the tendency of the lines which separate the different regions of the winds.

8. Thus will their force be broken and turned away from the houses and public ways; for if the directions of the streets be parallel to those of the winds, the latter will rush through them with greater violence, since from occupying the whole space of the surrounding country they will be forced up through a narrow pass. Streets or public ways ought therefore to be so set out, that when the winds blow hard their violence may be broken against the angles of the different divisions of the city, and thus dissipated.

9. Those who are accustomed to the names of so many winds, will perhaps be surprised at our division of them into eight only; but if they reflect that the circuit of the earth was ascertained by Eratosthenes of Cyrene, from mathematical calculations, founded on the suns course, the shadow of an equinoctial gnomon, and the obliquity of the heavens, and was discovered to be equal to two hundred and fifty-two thousand stadia or thirty one millions and five hundred thousand paces, an eighth part whereof, as occupied by each wind, being three millions nine hundred and thirty-seven thousand five hundred paces, their surprise will cease, because of the number of impediments and reverberations it must naturally be subject to in travelling though such varied space.

10. To the right and left of the south wind blow respectively Euronotus and Altanus. On the sides of Africus, the south-west wind, Libonotus southward and Subvesperus northward. On the southern side of Favonius, the west wind, Argestes, and on its northern side Etesi. On the western side of Caurus, the north-west wind, Circius, on its northern side Corus. On the western and eastern sides respectively of Septentrio, the north wind, Thrascias and Gallicus. From the northern side of Aquilo, the north-east wind, blows Supernas, from its southern side Boreas. Solanus, the east wind, has Carbas on its northern side, and Ornithion its southern side. Eurus, the south-east wind, has Ccias and Vulturnus on its eastern and southern sides respectively. Many other names, deduced from particular places, rivers, or mountain storms, are given to the winds.

11. There are also the morning breezes, which the sun rising from his subterranean regions, and acting violently on the humidity of the air collected during the night, extracts from the morning vapours. These remain after sunrise, and are classed among the east winds, and hence receive the name of eu\roV given by the Greeks to that wind, so also from the morning breezes they called the morrow aurion. Some deny that Eratosthenes was correct in his measure of the earth, whether with propriety or otherwise, is of no consequence in tracing the regions whence the winds blow.


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