5.  In the first book I have treated of architecture, and the parts into which it is divided; of the walls of a city, and the division of the space within the walls....  I must preface [this book] with an inquiry into the origin and various species of the earliest buildings, and their gradual advance to perfection.  In this I shall follow the steps of Nature herself, and those who have written on the progress from savage to civilized life, and the inventions consequent on the latter state of society.  Thus guided, I will proceed.

1.  Mankind originally brought forth like the beasts of the field, in woods, dens, and groves, passed their lives in a savage manner, eating the simple food which nature afforded.  A tempest, on a certain occasion, having exceedingly agitated the trees in a particular spot, the friction between some of the branches caused them to take fire; this so alarmed those in the neighborhood of the accident, that they betook themselves to flight.  Returning to the spot after the tempest had subsided, and finding the warmth which had thus been created extremely comfortable, they added fuel to the fire excited, in order to preserve the heat, and then went forth to invite others, by signs and gestures, to come and witness the discovery.  In the concourse that thus took place, they testified their different opinions and expressions by different inflections of the voice.  From daily association words succeeded to these indefinite modes of speech; and these becoming by degrees the signs of certain objects, they began to join them together, and conversation became general.

2.  Thus the discovery of fire gave rise to the first assembly of mankind, to their first deliberations, and to their union in a state of society.  For association with each other they were more fitted by nature than other animals, from their erect posture, which also gave them the advantage of continually viewing the stars and firmament, no less than from their being able to grasp and lift an object, and turn it about with their hands and fingers.  In the assembly, therefore, which thus brought them first together, they were led to the consideration of sheltering themselves from the seasons, some by making arbors with the boughs of trees, some by excavating caves in the mountains, and others in imitation of the nests and habitations of swallows, by making dwellings of twigs interwoven and covered with mud or clay.  From observation of and improvement on each others' expedients for sheltering themselves, they soon began to provide a better species of huts.

3.  It was thus that men, who are by nature of an imitative and docile turn of mind, and proud of their own inventions, gaining daily experience also by what had been previously executed, vied with each other in their progress towards perfection in building.  The first attempt was the mere erection of a few spars united together by means of timbers laid across horizontally, and covered with reeds and boughs, for the purpose of sheltering themselves from the inclemency of the seasons.  Finding, however, that flat coverings of this sort would not effectually shelter them in the winter season, they made their roofs of two inclined planes meeting each other in a ridge at the summit, the whole of which they covered with clay, and thus carried off the rain.

4.  We are certain that buildings were thus originally constructed, from the present practice of uncivilized nations, whose buildings are of spars and thatch, as may be seen in Gaul, in Spain, in Portugal, and in Aquitaine.  The woods of the Colchi, in Pontus, furnish such abundance of timber, that they build in the following manner.  Two trees are laid level on the earth, right and left, at such distance from each other as will suit the length of the trees which are to cross and connect them.  On the extreme ends of these two trees are laid two other trees transversely: the space which the house will inclose is thus marked out.  The four sides being thus set out, towers are raised, whose walls consist of trees laid horizontally but kept perpendicularly over each other, the alternate layers yoking the angles.  The level interstices which the thickness of the trees alternately leave, is filled in with chips and mud.  On a similar principle they form their roofs, except that gradually reducing the length of the trees which traverse from angle to angle, they assume a pyramidal form.  They are covered with boughs and smeared over with clay; and thus after a rude fashion of vaulting, their quadrilateral roofs are formed.

5.  The Phrygians, who inhabit a broad plain destitute of timber, choose natural hillocks, which they pierce and hollow out for their accommodation, as well as the nature of the soil will permit.  These dwellings they cover with roofs constructed of logs bound together, covered with reeds and straw, and coated with a large quantity of earth.  This species of covering protects the hut from the extreme heat of the summer, as well as from the piercing cold of the winter.  The weeds which grow in the vicinity of pools are used in other parts of the covering of the huts.  Each nation, in short, has its own way of building, according to the materials afforded and the habits of the country.  At Marseilles the roofs are covered with straw and earth mixed up together, instead of tiles.  At Athens, even to this day, the Areopagus, an example of remote antiquity, is covered with clay; and the house of Romulus in the capitol, by its thatched roof, clearly manifests the simple manners and habits of the ancients.

6.  It is from such specimens we are enabled to form just ideas of the early method of building.  Daily practice made the original builders more skilful, and experience increased their confidence; those who took more delight in the science making it their exclusive profession.  Thus man, who, in addition to the senses which other animals enjoy in common with him, is gifted by nature with such powers of thought and understanding, that no subject is too difficult for his apprehension, and the brute creation are subject to him from his superiority of intellect, proceeded by degrees to a knowledge of the other arts and sciences, and passed from a savage state of life to one of civilization.

7.  From the courage which his gradual success naturally excited, and his engagement in those various speculations with which the arts are connected, his ideas expanded; and from building huts he soon proceeded to the erection of houses constructed with brick walls or with stones, whose roofs were of timber covered with tiles.  Thus by experience and observation the knowledge of certain proportions was attained, which in the beginning were fluctuating and uncertain; and advantage being taken of the bounty of nature, in her supply of timber and other building materials, the rising art was so cultivated that by the help of other arts mere necessity was lost sight of; and by attending to the comforts and luxuries of civilized society, it was carried to the highest degree of perfection....

5.  ... in this [book] I intend to describe the arrangement of public buildings; and that of the forum first, because therein public no less than private affairs are regulated by the magistrates....

1.  When the forum is placed, a spot as healthy as possible is to be chosen for the theatre, for the exhibition of games on the festival days of the immortal gods, according to the instructions given in the first book respecting the healthy disposition of the walls of a city.  For the spectators, with their wives and children, delighted with the entertainment, sit out the whole of the games, and the pores of their bodies being opened by the pleasure they enjoy, are easily affected by the air, which, if it blows from marshy or other noisome places, infuses its bad qualities into the system.  These evils are avoided by the careful choice of a situation for the theater,

2.  taking especial precaution that it be not exposed to the south;  for when the sun fills the cavity of the theater, the air confined in that compass being incapable of circulating, by its stoppage therein, is heated, and burns up, extracts, and diminishes the moisture of the body.  On these accounts, those places where bad air abounds are to be avoided, and wholesome spots to be chosen.

3.  The construction of the foundations will be more easily managed, if the work be on a hill; but if we are compelled to lay them on a plain, or in a marshy spot, the piling and foundations must be conducted as described [in Book III].  On the foundations, steps are raised, of stone and marble.

4.  The number of passages ... must be regulated by the height of the theater, and are not to be higher than their width, because if made higher, they will reflect and obstruct the voice in its passage upwards, so that it will not reach the upper seats above the passages ..., and the last syllables of words will escape.  In short, the building should be so contrived, that a line drawn from the first to the last step should touch the front angle of the tops of all the seats; in which case the voice meets with no impediment.

5.  The entrances ... should be numerous and spacious; those above ought to be unconnected with those below, in a continued line wherever they are, and without turnings; so that when the people are dismissed from the shows, they may not press on one another, but have separate outlets free from obstruction in all parts.  A place which deadens the sound must be carefully avoided; but, on the contrary, one should be selected in which it traverses freely.  This will be effected, if a place is chosen wherein there is no impediment to sound.

6.  The voice arises from flowing breath, sensible to the hearing through its percussion on the air.  It is propelled by an infinite number of circles similar to those generated in standing water when a stone is cast therein, which, increasing as they recede from the center, extend to a great distance, if the narrowness of the place or some obstruction do not prevent their spreading to the extremity; for when impeded by obstructions, the first recoil affects all that follow.

7.  In the same manner the voice spreads in a circular direction.  But, whereas the circles in water only spread horizontally, the voice, on the contrary, extends vertically as well as horizontally.  Wherefore, as is the case with the motion of water, so with the voice, if no obstacle disturb the first undulation, not only the second and following one, but all of them will, without reverberation, reach the ears of those at bottom and those at top.