Engineering thinking in Rome

From various testimonies in the collection of books written in Rome, it appears that in addition to historical writing, legal writing and philosophical writing, books were also written in various engineering fields. The only book that has survived and reached us in its entirety is Vitruvius's book on architecture

A Roman water carrier in France, dating to 19 BC
A Roman water carrier in France, dating to 19 BC

introduction

From various testimonies in the collection of books written in Rome, it appears that in addition to historical writing, legal writing and philosophical writing, books were also written in various engineering fields. The only book that has survived and reached us in its entirety is Vitruvius's book on architecture. In this book, Vitruvius does not only describe and discuss the construction of various buildings and monuments, but also reviews various engineering fields. Beyond the historical importance of the book, it also allows for an introspective look at the world of engineering content of this period from the point of view of the planner and builder himself. This serves to provide an initial tool for testing and analyzing the entirety of the engineering thinking of this period.

The proper way to get a panoramic view of engineering in Rome is to follow all aspects of this field. The first thing to consider is philosophy, and this is for the reason that every technology must have a philosophical infrastructure. This is the foundation through which nature is observed, analyzed, rules formulated and then the mathematical formulas come. Roman philosophy is basically based on Greek philosophy and Vitruvius also follows this trend. This is seen in his reference to the theoretical aspects related to building engineering. Describing the Doric construction, for example, he explains: "When they wanted to place columns in that temple, they had no guidelines for the symmetrical proportions, and while they were looking for a way by which they could adapt to carrying loads, but also leave them beautiful to look at, they measured the footprints of a foot and compared it with its height. And so, when they found that a foot A human foot is one sixth of its height, adjust this ratio to the column and determine the height of the column, and the title in general, six times its height at its core" (p. 86). And it is true that Vitruvius states elsewhere that the proportions are the most important thing in building planning. "Once the module for symmetry is chosen, and the proportional measurements are calculated, the turn of thought comes to consider the nature of the place in relation to the question of usefulness and beauty" (p. 136). As implied by these words, proportions are of great importance, both aesthetic importance, both functional importance and pragmatic importance. Intelligent use of proportions also results in correct load distribution, allowing the lower parts of the structure to support the upper parts. Here, quite a few imitated the way plants grow "as, for example, in trees with round and smooth trunks such as the fir, cypress and pine, each of which is thick in the section above the roots and naturally becomes narrower with height in accordance with its growth" (pp. 106, 109). It may be that this way of thinking is the equivalent of the distribution of loads in construction and the calculations of quantities in our time. A particularly interesting statement is found in the introduction to his eighth book, in which Vitruvius says: "Everything born of the earth was consumed by the inevitable force of time and returned to it. Everything born of the air returned in a similar way to the elements of the sky. Nothing is lost, but changes and returns to the elements in which it was First" (p. 171). The surprising similarity of this formulation to the law of conservation of energy cannot be ignored. It is possible that a more detailed reference to this subject may be found in engineering books that have been lost and may be found one day.

Professional literature

The entire professional literature can be divided into 3 groups and they are:

1. Engineering literature that included 6 fields and they are- a. Literature on proportions such as that of Silenso who wrote on the proportions of Doric buildings. Philo who wrote about the proportions of temples and Arxius who wrote about the Corinthian proportions. on. Literature on symmetry written by Naxis, Theokides, Demophilus, etc. third. Literature on architecture written by Terentius, Publius Septimius, etc. d. A large part of Vitruvius's book is devoted to its building engineering. the. Water engineering - a field related to the transportation of water and it seems Vitorobius was the first to write about it in detail (pp. 184-190). Vitruvius does not give mentions of other authors on the subject. V. Mechanical engineering - Vitruvius mentions Hebrais who wrote on the subject such as Diades, Architas, Archimedes, etc. (pp. 153-154). G. Naval engineering - Vitruvius devotes very little to this field (p. 222) and he does not mention it from other authors. This is surprising because Rome was a naval power. It is hard to believe that there were no engineers whose specialty was building ships of various types such as merchant ships and warships. An auxiliary field that is probably included in some books is the drawings. It seems to have been a field that required extensive knowledge to the point of being a methodical discipline standing on its own. An allusion to this is found in Vitruvius' reference to the architect that he "must be an educated person in order to leave his writings in memory for generations, years, he must have knowledge of the theory of drawing so that he can easily prepare drawings to describe his works" (p. 24).

2. Textbooks - Vitruvius points out that architects must train, in order to be excellent professionals. "Only people properly trained in precise scientific methods will choose to engage in the profession of architecture" (p. 213). It is not enough to read appropriate literature, but one must obtain a formal qualification in order to engage in this profession. Vitruvius specifically states that textbooks were written for this purpose (p. 132). On his face, a picture is painted that there were study frameworks in Rome that trained professionals. It may be that in terms of their function they were similar to engineering schools. Vitruvius refers only to textbooks in the field of construction, since this is actually his field of expertise. It is not impossible that there were also textbooks in other engineering subjects such as mechanical engineering and ship engineering.

3. Geography books - Vitruvius states that various geography books were written, although he does not mention the names of the authors (p. 175). Vitruvius's emphasis in this mention is the rivers indicated and described in these works. His reference is indeed climatological, but it is likely that other reasons are involved. These rivers served as transportation arteries.

It is worth noting that Vitruvius did not lose sight of the legal aspect of books. Thus referring to Julius Caesar, he says: "But as for me, Caesar, I do not publish the essay in front of us by changing titles. Books written by others and writing my name on them, nor is this my way of gaining recognition by criticizing the ideas of others" (p. 153 ). In another place he states that just as athletes receive an allowance for the rest of their lives at the expense of the public, so writers should be rewarded (p. 191). These words of Vitruvius are similar to the concepts of intellectual property, copyright and writers' fees of our time. He basically makes a claim to the authorities not to deprive people whose literary work, their contribution is long-lasting, what's more, their books essentially serve the general public and that they should be rewarded accordingly.

Structural engineering

As you can see in the entirety of this work, Vitruvius devotes most of the book to building engineering and this is probably for two reasons. First, this was his field of expertise and secondly, the leading engineering branch of his time was the building branch. In this work, he refers to 3 types of buildings according to their intended function - residential buildings, temples and public buildings such as the treasury, the prison, the city council building, the baths and the theater. Each construction type had its own specifications derived from the function definition. At the same time, there were subfields that are required in all or most types of buildings and they are:

1. The stability of the ground - must be built so that the structure will last for a long time and this can only be done in a place where the ground is stable (p. 33).

2. Foundations - it is better to dig the foundations in solid ground - this is the ground whose stability is guaranteed. The depth of the foundations depends on the building that is going to be built. A large and massive structure requires a greater foundation depth and vice versa. "The entire foundation must be built as solidly as possible. And on the ground, beams must be placed under the columns whose thickness exceeds half that of the columns, so that the lower parts are stronger than the upper ones" (p. 77). If the ground at the construction site is not solid and is nothing more than loose dirt, or if it is sandy, it must be strengthened and stabilized artificially. It must be dug "uncovered" and piles made of charred alnus, olive, or oak wood must be installed. These must be stuck with a device in close proximity to each other, and the space between them must be filled with coal, finally the foundations must be placed on top of them in the strongest way" (p. 77).

3. Floor - Viturbius makes a distinction between several types of floors and they are stone floors (p. 62), gravel floors (p. 156) and wooden floors (p. 157).

4. Structure - Vitrubius distinguishes between two types of walls. One type is called a reticulum. It is a wall structure that has an aesthetic appearance and attracts the eye, but has a short lifespan. This is due to a construction method that causes it to crack "since its courses and joints extend in every direction". The second type of wall is called an incratum, which is more durable because "the field stones laid in its courses and cut-off joints form a strong wall" (p. 55). In any case, in both types of walls, the construction is done using stones made of a fine-grained mixture "so that the walls built mainly of mortar composed of blue lime will last a longer period of time. Since the stones used are soft and porous and are suitable for absorbing the moisture from the mortar and thus drying it, but if there is If lime and sand are found in abundance - the wall containing more moisture will not lose its strength so quickly, because they will strengthen it" (p. 55). Besides walls, the structure often included columns. These were made of hard material, wood or stone and were intended to support the roof. Their height far exceeded their width and the calculations regarding the dimensions of the column were based on proportions. To illustrate, we will present the way of planning a page from the generational style. "The thickness of the page will be two modules, and its height and the header in total - 14 modules, the height of the header will be one module and its width - two modules and a sixth module" (p. 92).

5. Roof - Vitruvius states that the upper part of all the buildings (p. 89) was made of wood when it was used differently in terms of the location on the roof and according to this a suitable nomenclature was born. The botanical nomenclature is not meant, but the functional nomenclature - for what purpose are they used during the construction of the roof. "The walls of the Sheti are those that are placed on top of columns, art, and entablature. The ceilings are made of shingles - roof and slabs. If the key roof is quite wide, there are link beams and reinforcement rods under the roof. If it is medium - only backbone beams and main diagonal beams, which extend to its ends, are On the outer edges of the roof, on top of the main diagonal beams, there are beams, and above these and below the roof tiles, there are beams. The diagonal and these extend to such a distance that their ends cover the beams" (pp. 89-90).

As for the decision-making process of the construction itself, 5 factors are taken into account, the weighting of which would ensure an optimal construction and they are:

1. Construction materials - Vitruvius distinguishes between 3 types of bricks used for construction. One type defined by him as Ludion and which is used in Rome and two others called one pentahedron and the other tetrahedron were used in Greece (p. 50). The stones were made from clay. For reasons related to the quality of making the bricks, their production was done in the spring. Production in this season ensures uniform drying of each and every brick, which guarantees its strength (p. 49). "Bricks will be most useful if they are made two years before use... It is true that in Utica, when building walls, they use bricks only if they have been made and dried for five years, and have been approved by the magistrate" (p. 50). Two very important things can be learned from this . First, preparing such large quantities of bricks over several years requires appropriate storage, storage methods and regular transportation to the various construction sites, which also requires a thorough understanding of logistical issues. It is not impossible that there were also those in Rome who specialized in this field and also wrote books on the subject. Second, the magistrate, by definition, supervises the construction and the quality of the materials. This is actually about quality control, which could imply standards set by the authorities and which were very strictly maintained. As for lime, Vitruvius distinguishes between two types of lime - lime suitable for construction and lime suitable for coating walls or ceilings and each of them requires the use of different types of sand and lime in different proportions (p. 52). A certain type of powder is also used that, if mixed with lime and fieldstones, gives strength to many buildings (pp. 52-53).

2. Lighting - the construction must be planned so that every house has maximum solar lighting. In rural areas no problem arises since the density of buildings is low. Not so in cities, where the density is high and the walls are high. The windows must be placed in all rooms. Their location must be done taking into account the goals for which they are built. Light from the east is essential for bedrooms and libraries, light from the west is essential in the winter season for baths and winter apartments, and northern light is essential for showrooms and pictures and places where stable light is not needed (p. 32). For safety reasons, light is also essential in passageways and stairwells to prevent collisions between people moving at all hours of the day with different loads in their hands (p. 144). The direction of the light must also be taken into account when planning storage spaces. The ideal light is the one coming from the north, such as wine cellars, barns and food and fruit warehouses. The latter "are not preserved for a long time unless they are stored in a place that is not exposed to sunlight" (p. 33).

3. Acoustics - Unlike residential houses where the rooms are inherently small, in public buildings the rooms are large and in fact it is more about buildings with large spaces such as buildings that have many halls and sometimes the spaces are open. It is also necessary to take into account the acoustics so that the speakers can be heard well. These are actually two types of buildings - public buildings and theaters. Vitruvius gives several examples of public buildings such as the treasury, the prison and the council house. Their inner walls should be covered up to half of them with a cornice made of wood or made of a sink so that the speaking voices will not rise in the air space and be dispersed. The tree or the crocus reflects the sound (in contemporary terminology - the sound waves) up to a little above the height of the people and everyone can understand everyone (p. 112). Another type of public building is the theater. Unlike other public buildings, where many people talk to each other, here only a small group of people, talk and everyone listens to them. The theater is actually a very large hall. The actors' voices may be scattered in the air without the spectators hearing them. To overcome this two techniques are used. One technique is to place sound vases (bronze or clay) between the seats to amplify the actors' voices (pp. 27, 116). A second technique installs the lines of the seats "so that a line that is drawn from the lower seat to the upper one will touch the edge and the upper corner of all the seats. In this way, no obstacle will stand in the way of the voice" (p. 113).

4. Climate - As for the style of construction, the geographical location must be taken into account. What is good for Egypt, for example, is not good for Rome or Spain. Each place requires a unique style. Vitruvius explains this in the position of the sun and its movement in the dome of the sky. "The design of the houses must take into account the nature of the place and its climate. So, for example, in the north, the houses must be completely roofed and protected as much as possible and not left exposed. But they must face the warm direction. On the other hand, Where the intensity (heat) of the sun is great, like the southern countries that suffer from great heat, houses should be built that are more open to the north and northeast" (p. 133).

5. The direction of the winds - during construction, the direction of the winds must be taken into account, since these have a great influence on the daily functioning of those inside them. Vitruvius makes a distinction between 3 levels regarding the planning of the construction location. The first level is the city level. Vitruvius's emphasis is on cities in forms. These should be built in a high place whose climate is temperate and far from swamps (pp. 33-35). If city fortifications must nevertheless be built near the marshes "on the condition that they are located near the sea and face the north or northeast, and are above sea level, then the site will be quite good, because canals can be dug and through them the water can be drained to the shore" (p. 35). This drainage ensures the elimination of those disease-causing swamp creatures.

The second level is the level of the streets - the planning of the city's streets (or the rows of houses according to Vitruvius' other terminology) will be done in such a way that the flow of winds between them is prevented or at the very least to weaken their strength. The accumulated experience of poor construction over generations has shown that this has a health importance. "We make our places healthy places for healthy people, but also in the case of illnesses, perhaps caused by poor location conditions elsewhere, the sick - who may in other healthy places get well through different treatment methods will get better here faster due to the mildness of the weather that comes from the removal of the spirits" (p. 39).

The third level is the level of the houses - the direction of the houses should be different from the direction from which the winds blow "this is so that winds will be prepared in the corners of the blocks of houses, their strength will be broken and dispersed" (p. 41).

Water Engineering

The Roman water works are works in which a lot of thought and planning was invested. The most striking example and which has been preserved for generations is the aqueducts that stretch for hundreds of kilometers. From a preliminary examination of them, one can see that whoever planned them knew how to handle highly complex projects that required a great deal of engineering knowledge, both in terms of establishing the water-carrying structures and in terms of securing the current flow of water. The Roman waterworks can be divided into two types. One type is the transportation system and the second type is the water treatment at the individual building level.

1. The transport system - this system begins with locating the sources of water, which requires geological knowledge that relates to the structure of the soil and the typology of valleys where water can be found, botanical knowledge that relates to the plants that are above sources of origin and astronomical knowledge that relates to the places that face the sun's orbit and beyond (p. 172-173) . At the same time as locating these sources, their quality was also checked (pp. 172, 182). Thanks to the accumulated experience of previous generations and their own and extensive geographical knowledge, the Romans could diagnose different types of springs such as hot water springs, cold water springs, sweet tasting water, salty tasting water, etc. Different types were designated for different purposes such as healing springs, bathing water springs, drinking water springs, etc. (pp. 176-177). The transportation itself is done using aqueducts built of stone, lead pipes or clay pipes (p. 184). Clay pipes should be preferred over lead pipes because the water passing through them is healthier than that passing through lead pipes, what's more, clay pipes are easier to repair. Anyone can repair them and there is no need to invite professionals every time to carry out repairs (p. 189). The pipes on the surface of the aqueduct must be covered so that the sun does not strike them (p. 185). That is to prevent heating and evaporation.

From the moment the water reaches its destination, it is absorbed by the water tower "to which a reservoir of 3 tanks is connected. 3 different pipes are installed to the water tower. A pipe for each of the tanks so that if the water overflows in the side tanks, it will flow into the tank in the middle. Pipes will be drawn from the central tank To all the basins and furniture: from the second to the bathhouses, ... and from the third ... to the private residences, not so There will be a shortage of water supply for public use" (p. 185).

2. The level of the individual building - at this level, Vitruvius refers to different ways of removing rainwater and baths. As for the removal of rainwater in the temples, in those rows of tiles above the pillars are drilled "holes that connect to the gutter that drains the rainwater from the tiles, but those between them must be left untouched" (p. 82). The result is that the rainwater drains into the gutter and not into the spaces between the columns, so those in these places will not get wet. In the private residences of the villa type, the interior space has a large opening designed to absorb rainwater and direct it to a basin in its floor (p. 273).

As for bathhouses, the arrangement of the water boilers was such that it was possible to obtain three degrees of heat (p. 126). The bathhouse had three water boilers, one for boiling water, one for lukewarm water and one for cold water. Their location was such that the water flowing from the hot boiler receives an equal amount of that of the lukewarm water and that of the cold water. In the bath house there was a system of clay pipes that would lead the hot air from the stove along the walls.

Mechanical Engineering

Vitruvius defines a machine as "a system of rods that has a special ability to copy heavy loads. It is brought into motion by the artificial motion of revolving circles known by the Greeks as koklica kinesis" (p. 214). This definition is different from the accepted definition today that a machine is a device for performing work. Although the machine according to Vitruvius' definition in moving loads from one place to another performs work, but this work is extremely limited. This difference in definitions must be understood due to the technological gaps between the periods and the different philosophical meaning that underlies the technologies.

As far as the philosophical concept behind mechanical engineering is concerned, "all mechanical theory originates in nature, and is guided and controlled by movement in the universe. Let us consider the mutual movements of the sun, the moon, and the five planets, without whose movement, which is mechanical in nature, we would not have the changes of day and night in our hands And not the ripening of the fruits in their season" (p. 215). The machines are actually mechanical mechanisms that imitate the movement of the celestial bodies for useful purposes. These machines were the product of the invention of previous generations. Vitruvius gives these generations full credit for these developments, not only from a philosophical point of view, but also from a pragmatic point of view. Whatever they found worthy of research, the arts and the applied sciences, they made sure to perfect it on the basis of scientific principles, step by step" (p. 215). Vitruvius makes a distinction here between useful science and non-useful science (what is nowadays called basic science or pure science), without detracting from the importance of any science that it is, and at the same time these two types of science rest on the same foundation, which is the sum of scientific principles, where progress is gradual from simple machines for increasingly complex machines.

Vitruvius makes a distinction between a machine and an instrument. The difference is in the number of people needed to operate. To operate a machine, a large number of skilled and powerful people are needed, and for a device, one person is enough to operate it (pp. 214-215).

In terms of the materials from which the machine was made, Vitruvius states that it was made of rods. He does not specify what it is made of wood or metal. It is likely that there were machines made of wood and machines made of metal and machines made of both wood and different metals. The surrounding lathe (p. 215, 267) that was used was intended for the production of wood, metal and stone tools. It is hard to believe that it was possible to shape metal and stone using wood. It is more likely that this operation was done using metals. From the various descriptions of the machines that Vitruvius mentions, it becomes clear that the machines also had gear wheels. Vitruvius refers in his book to 4 types of machines and they are:

1. Machines for lifting loads - in his description of the machines for lifting machines, Vitruvius defines types of loads according to their weight. The differences are relative and are heavy loads, heavier loads and loads whose dimensions and weights are enormous (p. 216), where for each type of load, there is a suitable machine for it. In general, the heavier the load, the more complex the machine. The design of the machines is done considering the weight and safety of the operators. There are no drawings here describing the machines. It may be that originally there were and they were lost. In any case, the lack of these burdens their translation into graphic descriptions, which give full details of each and every part of them. The machines for loads, whose dimensions and weights are enormous, require the use of different technology. A special type of machines made of a substance called polyspastine allows loads to be lifted and tilted in different directions as needed (p. 218). Referring to these things, Vitruvius notes that "two different things act in them as components of their movement and power, which due to their joint action produce these properties. One is the straight line, the other is the circle... At the same time, there is no power of linear movement without circular movement. or rotation without linear movement, to lift loads" (p. 220). In these words there is an explicit reference to the conversion of circular motion to linear motion. It is possible that in those books on mechanical engineering that were lost there was a more detailed reference, including drawings regarding this principle.

2. Machines for lifting and pumping water - Vitruvius describes 3 types of machines for lifting water designed according to the desired height. There is no reference to a specific height, but to relative heights. One machine raises to a low height and is designed to provide a large amount of water quickly and it is designed for gardens, for irrigation for salt water in ponds. Another machine is designed to raise water to a greater height and a third machine is designed to raise water to the greatest height (p. 224). These are actually large water wheels equipped with water tanks in different configurations. The first two types of machines are rotated by treading and in the third machine the rotation of the wheel rotates the chain around an axis and this raises the container upwards.

A special version of machines is the one placed in rivers. Around their perimeter are installed the pole plates with the water current "and when these are driven by the force of the river current, they turn the wheel. In this way, the water is pumped in coordination and carried up without the need for laborers for treading work" (p. 225). Water is used wisely here as a source of power, without involving people. The water is the operator of the machines.

Other non-wheeled water lifting machines are the Archimedes screw and suction pump. The Archimedes screw is a pipe along which there is an axis to which shelves are connected in a spiral manner and whose rotation of the axis causes water to rise. No such screw is capable of raising water to such a height as is done by a wheel. The placement of the screw between two sources of water must be done "at an angle identical to the angle created by drawing a Pythagorean right triangle" (p. 226). That is, it is a triangle where the screw is treated as a 5-part side. When the base of the triangle has 4 parts and the height of the triangle (the height difference between the lowest water source and the place to which the water is transported) is 3 parts. One can clearly see the application of mathematical knowledge to engineering needs. Another type of machine is a suction pump that supplies flowing water from a reservoir located at a low level (pp. 227-228). This pump is an array of horizontal cylinders connected to perpendicular cylinders, inside which are valves and pistons. The pistons work by means of rods and levers on the air and water in the cylinders, by means of the air pressure they are pushed upwards. Unlike the other machines for lifting water and pumping them made of wood, the suction pump is made of bronze. This is to testify to the discernment of the Roman engineers regarding the limitations and advantages of using the various raw materials that were at their disposal. Even if Vitruvius does not say so, it seems that he and those who developed the suction pump had an understanding that air as a material can be used in engineering.

3. Stage machines for the theater - these are actually triangular prism-like platforms that are inserted into the stage using cranes above the back wall. The base of the platform is a triangle that rotates on its axis, with a decorated wall attached to each of its sides. The platforms were used to bring actors onto the stage and the decorations were used as part of the scenery (p. 120).

4. War machines - Vitruvius gives a brief description of the subject, although regarding a number of machines such as catapults, catapults and rams, he gives detailed numerical descriptions (pp. 237-239, 231-235). Since the original drawings that originally accompanied the book have been lost, deciphering their structure according to Vitruvius' descriptions is very difficult. Anyway, the Romans had different machines that they used in their wars. Some of them are the fruit of the development of the Greeks who were adopted by them. As for the siege forces, it is possible to follow the course of their development. Siege rams were already found in use by the Assyrians and Babylonians and it seems that Vitruvius was not aware of these historical facts. His starting point is the First Punic War (p. 236) and over a page and a half Vitruvius gives a brief overview of the history of the siege giants (p. 236-237). The design of the weapons was done in three stages. In the first stage, the drawing stage - in the description of weapons, Vitruvius does not refer to drawings at all. From what we have already seen we know that those who studied civil engineering also studied the art of drawing. There is no possibility of planning a building without the planners having diagrams describing the building in its final form. The same goes for the war machines. These were most likely found in the works of engineers such as Dyades (p. 236), on which he bases this chapter. Second stage - the stage of building the models. Based on the drawings, various models were built on a reduced scale to show the programming of their operation (pp. 240-241) and the third stage is the construction of the machines themselves. The engineers knew that there were differences between the performance of the model and the performance of the full-size machine. It is likely that in these models and in light of the accumulated experience, that there was an intermediate stage between the functions of the models and the functions of the full-scale machines and that improvements were introduced in the models that were implemented in the machines themselves. From the lines it appears that there was a distinction between war machines intended for attack and those intended for defense (p. 236).

Vitruvius distinguishes 5 types of war machines and they are the catapult, the catapult, the battering ram, the tower and the turtle. The catapult was a machine for throwing arrows. These were longer arrows than those shot by a bow. The manually operated catapult and arrows are hurled at much greater distances than those hurled by a bow. Such a machine could throw at least two arrows at the same time. "The proportions of these machines are all calculated according to the length of the arrow intended to be thrown from the machine" (p. 232). The direction of the throwing of the arrows was determined by the strings of the catapult "and thus while the strings are stretched by the hand levers, when they are struck by hand they produce an equal sound from each side. Then they are reinforced in places with wedges so that they do not loosen. In a similar way they are moved to the other side, coiled on top of the winches and stretched using the hand levers until they produce the same sound, and this is how the catapults are adjusted using the wedges to the sound the correct one through the musical ear" (pp. 235-236). Operating the catapult therefore required a great deal of professional skill. These are apparently people who have been specially trained to operate these machines and have a very sharp ear. The greater the tension of the strings, the greater the distance the arrows were thrown.

The catapults are stone throwing machines. In the same way that the length of the arrow is used as a standard for the manufacture of catapults, so the measure of the weight of the stone that the catapult is designed to throw, and the measure of gravity are used as a standard for the manufacture of the catapult (p. 234). There are therefore different catapults designed for different throw weights. Hence the conclusion that light and heavy catapults were used. In the distinction that Vitruvius makes between measure of weight and gravity, it can be seen that the Romans probably distinguished between the mass of the material and its weight. The siege ram was used to break through wall gates and demolish them. The first siege rams were wooden beams carried by several warriors. More advanced besiegers were already "motorized". They were placed on wheeled platforms. Another machine was the tower. It was a high platform with several floors. Downstairs was the battering ram. On this floor and the floors above there were water reservoirs intended for firefighting. On the upper floor were catapults and scorpions (semi-automatic bow for manual operation) (p. 237). The battering ram could be moved back and forth using ropes. The tower was actually a multi-purpose vessel - a platform on which several war machines were placed. The turtle was a tool with a service function. It is "intended to fill moats and thus (intended) to allow access to the wall (p. 237) "and it can move forward or backward or side to the right or left" (p. 238). The side was done using levers that were moved through holes that allowed the rotary movement. Model Another of the turtles had 8 wheels that could be adjusted to the ground conditions (p. 238). Different types of wheels were probably made - for rough ground and for less ground Offense This intelligent use of wheels seems to have been applied to towers as well.

Marine engineering

In this area, Vitruvius referred to two issues, namely the construction of ports and the operation of ships. As for shipbuilding, there is almost no reference on his part. This can be explained in two ways. Either he did not know the subject and therefore preferred not to deal with it, or he did not have enough written sources for him to try to summarize and summarize them as he did in the description of various war machines.

From Vitruvius' words it can be seen that there is a distinction between a natural port and an unnatural port. A natural harbor is a harbor located near "promontories or end cliffs whose natural shape curves inward (p. 128). The advantage of such a harbor is that it is protected from storms. On the docks there are installed "towers between which chains can be stretched using machines" (p. 128). These natural ones do not exist, work must be done to establish an artificial harbor The essential landscape items are a river or an anchorage in the past. In the case where there is only an anchorage, one must start from the other end and thus the closed harbor will be created (ibid., p. 128). Vitruvius gives a very detailed description of how to build these walls. As for the walls themselves, they are made of a mixture of mortar, lime, and field stones, the peculiarity of which is that it hardens Under water, to the extent that neither the waves nor the force of the water could dissolve them (p. 53). It seems that the specific combination of these materials, which Vitruvius does not mention, was arrived at by trial and error. In connection with the anchorages themselves, it is important to build them in the north direction and this For the reason that exposure to the south will "result" in the formation of rot and the reproduction of woodworms that will gnaw at the ships. The use of wood must be as minimal as possible since they ignite easily and their dimensions must be such that they can withstand the load of the largest ships (p. 129).

Vitruvius does not speak about how these ships were built. A single mention that has a bearing on this is regarding their internal space, when he states that there must be symmetry from the space between the oar grips (p. 31). Since this is something general, it seems that this is a construction rule that applies to any ship. A more detailed reference concerns the navigation of ships. A distinction must be made between sailing within ports and sea sailing. Inside harbors, the philosphaston machine, in which a system of rotating wheels and ropes, can be installed horizontally on a rotating platform that enables ships to be towed to shore (p. 218). Here, knowledge from the field of mechanical engineering is applied to the field of marine engineering. Sea sailing is done using sails and jibs and the way they are raised, their position on the ship and their deployment require a great deal of skill in order to gain maximum wind speed (p. 222). The distance of the oar blades from the side of the ship affects its speed. "If the blades are far from the center, they row in the foam of the sea waves and push the ship forward with great force and in a straight line, while its prow crosses the water" (p. 222).

It seems that the Romans had some knowledge about refraction of light. A ship's oars "until the moment they touch the surface of the water they appear straight, as indeed they are, but as soon as they sink into the water, they emit from their bodies a flashing mirror which rises to the surface of the water through the naturally transparent substance, and there, when disturbed, it makes the oars appear broken " (p. 136). It is possible that this phenomenon was taken into account in order to determine the distance of the blades of the oars from the side of the ships.

Summary

A careful examination of Vitruvius's book and a retrospective look at the Roman engineering enterprise, a part of which has managed to be preserved to this day, shows how great the treasure of Roman engineering knowledge was, even if it was based on earlier knowledge, in particular the Greek one. The Romans knew how to take the Greek knowledge, improve it and perfect it for generations (you can define it as a kind of technological evolution) and also developed their own things. The presentation of knowledge as expressed in this book is very systematic and comprehensive and it is possible that in the engineering textbooks the presentation of knowledge was also methodological. A hint of this can be seen in the splitting of knowledge in the various fields into sub-fields such as building engineering and water engineering. The treasure of knowledge does not remain a domain within itself. Sometimes it was used more widely - mathematical knowledge was applied, for example, in the Archimedes screw and the knowledge that was used to make machines and lift loads was also used in the engineering of seaports. This can be understood against the background of the pragmatic approach of the Romans to use the knowledge they have in an optimal way. An interesting thing in this book is that the measuring tools that Vitruvius mentions have a clear affinity to building engineering. For some reason he does not mention measuring tools that were used, for example, in mechanical engineering. There may be a mention of them in lost books.

The philosophical basis of the Roman treasury of engineering knowledge is different from ours, and sometimes there are allusions to some vague knowledge or intuitively felt knowledge that could lead to modern philosophical concepts such as the law of conservation of matter, the distinction between weight and mass, and refraction of light, knowledge that they sometimes knew how to put to practical use. The conclusion that emerges from these words is that even if the philosophical basis is different from that of modern times and to the extent that it has a consistent and systematic thought rationale and knows how to put it into practice from the theoretical idea to the practical, then it is possible to achieve technological achievements that are more than impressive.

מקור

Vitruvius-on about architecture Dvir publishing house 1997

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