ANCIENT SRI LANKAN TECHNOLOGY
Sri Lanka is one of the few countries in the world which has a recorded history over more than 2500 years. It could also be proud of its unparallel Hydraulic Civilization dating Back, almost for the same period. The ancient Sri Lankans have aptly demonstrated highest form of engineering and technological skills in their achievements in Water Resources Management, Construction of Large Trans Basin and other River Diversion Schemes, Weirs, Dams, Embankments, Reservoirs, Conveyance Canals, Weirs, grandiose Stupas, Shrine Rooms, Buddhda Statues, Palaces & Monasteries, Pleasure Gardens, Rock Fortresses, Rock Inscriptions, etc.
The main materials used in engineering works by our ancestors were entirely the indigenous materials, and mainly consists of 4 types,
- Earth
- Bricks
- Stone
- Timber
And also iron manufacturing was an important technology which was used in Sri Lanka in 3rd century. For an instance wind powered iron smelting furnace was found in excavation done at Samanalawewa area. Those were plenty high quality carbon-steel was mentioned the Syrian history. Early wind-blow steel manufacturing was not acceptable by the world, but after experiment done, implemented structure using results was exactly working.
By using these materials, our ancestors have done lot of engineering works in this small country. Using bricks they have built stupas, palaces, etc. And from stone, they have made statues, bridges, etc. And by using timber, they have created bullock carts for their transportation.
The main reason for these kinds of creations and innovations was to make their day to day work easy and with a view to uplift their living condition. It was vital to satisfy the loyal needs as well. When considering engineering aspects experiment and analysis, they have used some advanced mathematics. And they had a proper knowledge about Geometry, Astrology, Trigonometry and Behavior of materials. Most important thing was they managed the environment properly without affecting it badly.
Some of their innovative creations, we have discussed here in this project by referring resources such as books and internet.
ANCIENT IRRIGATION SYSTEM
Sri Lanka is a classic example of the "hydraulic civilization" which had developed in the ancient period. With the immigration of Aryans from Eastern India to Lanka in 543 BC, cultivation of rice developed into a grand scale in the island. As the new essentially agricultural Aryan civilization flourished, increasingly ambitious projects of irrigation were launched at a pace with a view to harness the monsoon rains. It can be safely deduced that the first great reservoirs ever in the world were built in Sri Lanka. Since the great lakes of Egypt, being merely natural hollows into which streams were turned do not fall into the category of man-made rainwater reservoirs as those of Lanka.
The main reason for this classic huge irrigation system is our ancient people's main income way. It means Agriculture. To do this, most suitable area was dry zone. But unfortunately they had not enough water to continue that. Although they got water from rains, it was not sufficient. Our kings understood this problem and they were searching for a solution. They finally thought that this rain water flows to the sea without any use. After that they try to gather the water without letting to flow.
It wasn't easy job to do. Sometimes water flew rapidly. In such cases it was a hard job. When our people were up to stop a river they had to dedicate their lives too. But they never gave up this challenge. They finally built a "DAM" across the river. That was a fantastic engineering work of our forefathers. Because of on those days, they hadn't any knowledge about the water pressure and how it varies with the depth. Their technique was keeping a foot of soil and making it an inch. Like that they built up large dams across number of rivers. The special thing was during those days they hadn't any vehicles or modern instruments. The only thing they used was man power. Up to now also we can't see any fault or leakage of those dams.
There are so many examples for such dams. One of them is dam for "Tissa wewa". It was built by king "Dewanampiyatissa" in 3rd BC. It is 1.75miles and tissa wewa has water for 2900 square feet and also it helps to a huge area to do people's paddy fields. And another example for a dam is "Basawakkkulama wewa". The length of its dam is 3900 feet and it has water for 1900 square feet and it is also contribute for a huge area.
And another famous example is "Parakrama Samudraya". People called it "Samudraya" (Sea) because it is too large than the others. The length of its dam is 12.38km and maximum height of it is 9.45m. Its water covers an area of 2539.5Hec. When the tank is full, it has water for 109000 square feet and it can contribute for a huge area. To take water to the paddy fields, there is a well planned system. There is a main lake with the length of 16.5miles and it has another smaller lake with the length of 31650 feet. After that to take the water into the paddy fields, there are so many small lakes with the length of 385000feet. It is amazingly done by them without affecting to the land areas. This is how they made the tanks to help their jobs themselves.
When they wanted to take water through the lakes from the tanks that were made by them, they were thinking that how to get it without being any damages. Then they made sluice gates (In sinhala called "Sorowwa"). Not only one sluice gates for a tank there at least two or three sluice gates for a tank. They had made those sluice gates as they want, like when they want water to area which too long from the tank or too close to the tank. One of such system can be seen in "Parakrama Samudraya". There are three sluice gates. One of them is 51.51m in height from sea level and other one is 51.8m from sea level. Like that, they made sluice gates for each tank with the knowledge of water pressure they gained when they were making tanks.
But unfortunately, when the water came out from the sluice gates it was uncontrollable. It was too hard to control the water. Then they thought that they could not do this with only sluice gates so they tried to reduce the speed of coming out water. So they made the unbelievable creation which has a huge engineering background. That is so called "Biso Kotuwa" (Queen Enclosure).Associated with some ancient tanks provided with stone amicus is this concept of the time honored device of a Biso Kotuwa. This ancient irrigation artifact is rectangular in shape of well dressed stone slabs has served as a marvelous contraption of invention of the time. Its purpose was to store irrigation water for the purpose of stopping the overflow of the water conveyed along a stolen aqua-duct in regulating its flow of water to feed the vast tracts of rice fields. Still another purpose was prevention of silage. Hence this sprawling Walawe Basin nestling in the cradle of our ancient civilization in Ruhuna Rata and Sabaragamuwa has turned into one of the bountiful rice bowls of our isle, teeming with multitudes of farming communities and a host of industries could aptly boast of such relics of a past hydraulic heritage.
This Biso Kotuwa through which was let out water into the channels had its base or floor of about fifteen fathoms square paved with quarried stone, waterway or gutter conducting the water through the Biso Kotuwa through which was 3 1/2 fathoms long, 1 1/2 wide and 1 1/2 high on all sides closely. It was of 2 1/2 by 3 feet to admit the passage of man. There were two sluices, the entrance to each of which were called Wanaya and were undoubtedly of wide influence. There is still another similar authoritative source reference culled from H. Parker of British times who served in Ceylon (Sri Lanka) as an Irrigation Engineer (in 1901). In his voluminous monograph titled "Ancient Ceylon" (1909), he has paid accolades to our ancient Sinhalese Irrigation Engineers thus "The Valve Pits/Valve Towers of modern times by which the overflow in large reservoirs are regulated or totally stopped. Since this being the case the ancient Sinhalese Engineers in constructing such Biso Kotuwas had established a claim to be considered the first Inventors of Valve Pita more than 2,100 years ago.
In archaeological terms such Biso Kotuwas had the function of releasing the water by either regulating or stopping its flow completely. It had another romantic state in Royal flavor in those halcyon days when our ancient kings and queens ruled in all glory and splendor. A similar rectangular tank dressed with stone was constructed, fed by some natural spring or some rivulet, where queens and princesses bathed and frolicked in the filled up ponds.
In 1952, modern Gal Oya Scheme testified to the brilliance of the ancient masterminds of irrigation engineering in Lanka: the discovery of remnants dated back to 1500 years of a dam site and two sluices almost exactly at the locations determined for the new reservoir by the engineers at the Gal Oya project. In order to preserve the excavated ruins of the dams & sluice gates, the priceless archeological findings, the government decided to move the new dam site to another location.In 1978 when modern engineers cleared the jungle to pave the way for the modern Maduru-Oya reservoir they stumbled on an ancient breached earth dam at the very spot where engineering experts had decided to straddle the river. This dam a little over 23 meters high has been dated to be over 2000 years old & indicates the existence of a vast reservoir before its breach.
This is how our ancient people have done such kinds of huge engineering works to make easier their lives and to make an unbelievable contribution to the agriculture. So we should not forget that we have lot to learn from our history as engineers.
BULLOCK CART, THE VEHICLE OF ANCIENT TECHNOLOGY
Engineering technologies that were used by ancient Sri Lankans can be discussed with regarding to the topic 'Transport'. As a result of the simplest bullock cart to brigades of army ships, we are left in a state where it is unavoidable in being surprised about the technologies and methods that were used by our ancestors. Here in this session, I'm trying to explain how technology was used to improve the quality of the bullock cart that they used in day to day activities to enhance development.
There are few types of cart used by our ancestors. Horse and elephant carts were used in wars and by noble citizen. A small model of cart called 'Thirikkalya' was used for travelling and races. But the bullock cart which is also known as "Gon Karaththaya" was the main and common vehicle of ordinary people used to carry heavy loads. Normally it consists of two wheels and can be pulled by 1 or 2 bullocks.
In the bullock cart, the wheels are not vertical as it should be. They have some angle as shown in the figure. Because of the method that has used to fix the wheels to the axle, wheels can rotate about the horizontal axis but not about the vertical axis, and this allows the cart to swing. Even though this causes the cart to be a little uncomfortable, it has more engineering benefits than apparently visible.
For an example, consider a situation like one wheel is in a pot hole or on a rock as shown in figure. If the gravitational centre of the load is not on the line of axle, the horizontal component (W) of the weight and the friction force (F) can create a moment (G). And this creates an extra exertion (F') on the bullock and makes it tired. But since the wheels had been fixed in that method, they can rotate about their centre as well as the points on the floor. Therefore, the whole cart can swing to the direction of the force before it is balanced under the moment. Later it returns to its normal state when it is on plane ground. Of course it's only a short time that the cart can swing without creating a moment, but it's enough to return to normal state.
This method also offers some sort of a suspension system to the cart. When one or both wheels suddenly fall into a pot hole, those wheels immediately get vertical and later take their normal positions slowly, allowing the cart fall slowly. This makes the journey comfortable.
Another important technical part of the bullock cart is the breaking system. Normally it's a bunch of wood, tied up with a rope and laid behind the wheels. This acts as a 'block' (called 'adaya') to prevent the cart to go backward unnecessary. This really helps a cart which has to climb mountains with heavy loads. If the bullock had to stop for some reason on the way, this system stops the cart going downward. It's a good support to the cart rider as well as the bullock to handle the cart properly.
Our ancestors who practiced Buddhism thought about the ease of the bullock as well as their benefits which lead to the design of such a system. The swingy motion of the cart represents the cart rider's life and it must have been helpful to create various rhythms for the 'Gal Kavi', which helped the growth of our literature.
The breaking system helps the cart to climb even the mountains which have a steep slope easily. Therefore, productions of the coastal region could be carried to the up country with ease and greatly benefitted the local economy and improving it.
Understanding the theory and functionality of this once existing system is very easy, but designing such a system is really difficult. That's why we must admire our ancestors who designed such a vehicle with simple yet extremely efficient techniques.
STUPA, THE MONUMENTS OF ANCIENT TECHNOLOGY
The greatest monument in Sri Lankan history was stupa. It was very complex solid structure built by ancient engineers. First stupa was Thuparamaya. But very large scale construction had begun from king Dutugamunu which was Ruvanvelisaya 298 feet broad and about 300 feet high. Jetavana stupa built in the third century AD was the tallest brick building in the world at that time. Abayagiriya stupa is
also very large structure. And also there were so many stupas built all over the island. Comparing height of Jetavana stupa was second only to the Pyramids. A stupa
has a more complicated shape than a pyramid, and ancient engineers of Sri Lanka have shown much technological as well as management skills in the construction of large stupas. And also there were strict supervision and quality control. Ancient engineers knew about load, stress, height, span, stability, electricity of lightning. They used framed as well as load bearing and earth compacted structures. Some of their technological skills are discussed bellow.
They had good knowledge about materials and their functions. They used different materials for different purposes. Brick was made from mxture of clay and sand. Metals are used for various purposes. Iron used for making equipments and foundation of stupa. They used copper for Chattra. And also according to mahavamsa they used copper and silver sheets for foundation. The mortar was a mixture of lime, sand and water, used to hold bricks.
Great care has been taken in selecting the sites and laying out the foundations. Most probably they were done soil test for select the site. Otherwise stupa couldn't withstand for long time period without collapsed. Most of the times they used site which was near to the wawa. This is because there was enough clay for bricks and water supply for the construction. And also most stupas have been founded on rock and for others elaborate preparations of the foundations have been made. Construction of the foundation was one of the most important parts of the
stupa. Because whole weight of the stupa acting on this.
Mahavamsa describes how the foundation of the Ruwanveli stupa was laid,
" The king commanded that the clay be spread over the layer of stones and that bricks then be laid over the clay, over these a rough cement and over this cinnabar, and over this network of iron, and over this sweet-scented marumba that was brought by samaneras from the Himalaya. Over this did the lord of the land command them to mountain crystal. Over the layer of mountain crystal he had stone spread; everywhere throughout the work did the clay called butter clay serve (as cement).With resin of kapita-tree, dissolved in sweetened water, the lord of chariots laid over the stones a sheet of copper eight inches thick and over this with arsenic dissolved in sesamum oil,(he said) a sheet of silver seven inches thick...."(Mavavamsa XXIX7-12)
This description suggested that they used reinforced concrete foundation with damp proofing.
The main building block of a stupa is the brick.In the early days they used mud brick. But then they used burnt clay brick which had more strength than mud bricks. Different sizes of bricks have been used in different components of the stupa. Dome, the most bulky component of the
stupa, has an outer layer of high quality bricks of large size, and towards its inside brickbats as well as earth has been used in some cases. In recent times, when the Jetavana stupa was being renovated, structural engineers were found that the existing shape was the most suitable for that particular mix of brick and clay mortar and that it would give the best strength. In some cases bricks were found in the foundation to prevent the Ingress of moisture to foundation. Ancient bricks from various stupas were tested for their mechanical properties. According to mechanical properties it is seen that ancient bricks are of much higher quality than the modern bricks. In the case of Jetavana stupa, a linear elastic finite element analysis under self weight gave a maximum compressive stress of 839 kPa at the bottom centre of the dome and no tensile stresses in the dome .Hence the maximum stress in the dome is less than one tenth of the strength of ancient bricks used. There are tensile regions in the square chamber having tensile stresses reaching a maximum value of 40 kPa, which is also very low compared with the tensile strength of ancient bricks. These results show that the ancient brick had much higher content of sand than the modern ones, and that may be the reason for the higher strengths of the ancient bricks. The ratio of silt to sand is even in the ancient bricks perhaps indicating better quality control in ancient brick making.
The shape of the dome was different from one stupa to another. But there were mainly six types. The dome is a perfect solid of revolution, which is an ellipsoid for the Jetavana stupa
and a paraboloid for the Abayagiri stupa. paddy-heap shape is the most common one .Because for paddy-heap shape domes the stresses are all compressive, making them the most stable from a strength point of view. Since seismic effect is minimum in sri lanka the main loading on a stupa is its self weight.
Finite element studies done on stupas have shown that, under self weight, most parts of a stupa are under compression. Few tensile zones are present in the square chamber and the cylinders, and at the outer surface of the domes having shapes other than the paddy-heap. The surface of the dome was plastered with a thick lime plaster to prevent ingress of water. Essentially they have to use mathematical knowledge and equipments to maintain the shape of dome and orientation of the stupa. The stupas are oriented along North-South East-West axes, and setting out has been done very accurately. In Abayagiri (present height 73.0 m, outer basal ring diameter 108.8 m) orientation of the boundary walls are within 1.5 degree accuracy and the top of the spire is almost in the same vertical line passing through the centre of the base (maximum shift is 23 mm)
And also they had some knowledge of electricity of lightning. Therefore they used copper Chattra to drawing the charge from cloud and grounded it.
There is special thing such that couldn't explain in modern science. That is there exists a perfect alignment of the three main stupas (Mirisavati, Ruvanweli and Jetavana) at Anuradhapura, with three stars in the constellation of Orion, namely Rigel, Al Nitak and Bellatrix. That means that the three sides of the triangle in the ground layout of the three stupas, are correlated precisely with the three sides of the triangle of three stars on the right-hand wing of the constellation of Orion.
Stupas were built for religious purposes. But it was provided carrier opportunities for ancient engineers, architects, mathematicians and labors. According to the mahavamsa when the mahatupa was built there were no forced labors, and workmen were paid. Jetavana stupa built in 27 years required a total of around 62 million bricks. Considering 230 working days per year, this required the laying of 10,000 bricks per day. Making these bricks and transporting them to site, let alone laying them with mortar would be a massive task undertaken by the builders of the 3rd century AD.
ANCIENT WIND-POWERED STEEL MANUFACTURING TECHNOLOGY
Our forefathers were genius in handling nature with out doing any harm or destroying but utilize the nature magnificently as it is. This is something of that kind, is nature of the wind-powered furnaces, this innovative technology could have sustained an industry producing at least 10 tons of steel a year, a tremendous output for the time was revealed mainly in excavation done at Samanalawewa area. From June to September, powerful monsoon winds blow steadily off the Indian Ocean, lashing the slopes of the hills and ridges of Sri Lanka facing the southwest. The winds dump torrents of rain on parts of the country, while leaving the rest blow-dried. In the dry region of Samanalawewa, archeologists have found surprising evidence that the monsoon was a driving force stoking South Asia's pre-eminence in steel production in the first millennium A.D.
Archeologists who involved have identified there the ruins of 41 iron-smelting furnaces that appeared to take advantage of the prevailing wind to produce high-carbon steel through a previously unknown technology. Tests with replicas of those furnaces revealed the principle underlying the technology that used natural wind-pressure to create a dependable draft for keeping charcoal fires smelting hot and demonstrated its ability to produce substantial amounts of quality steel.
By the time most of these types of furnaces were operating, from the 7th to 11th centuries A.D., iron was being produced through much of the world, as well as steel, which is an alloy of iron and carbon from the charcoal. But the most prized and widely traded were the steels of our motherland and India, their qualities praised in Islamic literature. Some of these furnaces could have been sources of steel for the legendary Damascus swords, known for their sharpness and durability. A survey of the region, identified 139 iron-working sites spanning 2,000 years, at least one possibly dating back to the third century B.C. judging by the number and nature of the wind-powered furnaces, this innovative technology could have sustained an industry producing thousands of tons of steel.
In a well-known research west-facing site was chosen for the experiments and two new furnace structures were built. In the first instance the furnace was constructed using the original position of an ancient furnace on the site. This guaranteed the correct orientation of the furnace, relative to the incident wind, for that site. It had been observed from the archaeological evidence that the precise positioning of furnaces varied by several degrees from site to site. Wind direction measurements taken from the sites revealed that the immediate local topography had a considerable influence on the direction of incident winds at different locations, at some sites being predominantly west- northwest, at other being west or west-southwest. The furnaces were constructed according to the archaeological evidence and attention was paid in recreating the exact size and shape of the furnace.
Of the five trials conducted only the last three, trials 3, 4 and 5 were full smelts. The first two trials were designed to test the durability of different clay mixtures and to gain experience in lighting and controlling a fire in high winds. Throughout each smelt Wind speeds were recorded at 15 minute intervals and during the last trials, trial 5, Temperature readings were taken every hour using an optical pyrometer and by sighting down the tubers into the hottest part of the furnace. So that the trails could be compared one against the other the same operational procedure was followed throughout and variation from trial to trial was restricted to changes in wind speed, which was beyond control, and progressive intentional changes in ore to charcoal ratios On the day of the trial the base of the furnace was first lined with a layer of paddy husk followed by a layer of paddy straw, in accordance with the archaeological evidence. A layer of charcoal was then added and the fire lit. Once the fire was established more charcoal was added until the furnace was full to the rim. The furnace was maintained in this way, with charcoal only,for two hours. This both heated the structure of the furnace and created a deep bed of burning charcoal. Smelting begins with the addition of the first of four pre-weighed ore/charcoal `charges to the top of the furnace. For another one-and-a-half hours after which no more charcoal was added. After a further hour or so, the level within the furnace had burnt down to half the furnace height and at this point the furnace was opened by pushing the front wall inwards using long wooden poles. The contents of the furnace, hot charcoal, slag and metal, were then dragged out of the furnace, again using wooden poles and the lumps of metal were separated out.
Subsequent examination and analysis has shown that, while approximately half the metal produced is the typical low-carbon wrought or `bloomery iron mixed, with considerable amounts of slag expected of pre-modem bloomery smelting, the remaining material is relatively slag-free, homogeneous high-quality, high-carbon steel.
The above archaeological and experimental data described have demonstrated and proved, for the first time from anywhere in the world, the successful use of wind in iron smelting. Prior to this work it was generally believed by metallurgists that wind-powered smelting was not possible. That is the important to be mentioned here is our forefather's innovative ideas sometimes not seized by common sense.
Reconstructed sketch using archaeological data
Then we must see how steel manufacturing satisfied the society needs as well as local and abroad. Economic aspect is vital while analyzing the engineering aspects because those should be feasible and how it improved the living condition of human.
Metallurgy industry facilitated huge range of requirements of the society. Every need beginning from the king to farmers, cultivators was regarded with metals. And the contribution they gave was very vital. New metal innovative tools and equipment enhance and made their day to day works easy. With the advent o those people needs got more complex figure. Jewels for king queen, prince, princess , arms for loyal army, agricultural equipment, kitchen hold tools, carts and animals foots in transportation, as a media used in pagodas and palaces, exporting media to other countries….are obviously occupied major services given by them to the society to up lift and to make easy their life condition as well as safety. These are evidences which well show what a brilliant technology, what a brilliant innovative thoughts we had in ancient time. It exactly may be much useful to us as engineers how they did their experiment, analysis, seeing whether they can achieve their target well. They taught us don't waste any thing even a little wind blow with out utilizing it usefully, thoughts can be a real one day.
REFERENCES
- CHS Newsletter No. 70, December 2004, London, Construction HistorySociety.
- http://www.lankalibrary.com
- G. Juleff, "An ancient wind powered iron smelting technology in Sri Lanka"
- 'Karaththayen Heliwana Ape Ingineru Sampradaya' by Eng: Kapila Pieris and Eng: Chandana Jayawardena (SLEN)
- Prof.H.T.Basnatake,"Purana Sri Lankawe Jala Sishtacharaya"
- http://www.sundayobserver.lk (2008-10-05)
- Shereen Amendra:THE MAHATHUPA OF LANKA"
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Many shanty people had built their houses and make shift toilets on water-ways of the canal. Bere Lake is a good example for that. Because most of the waste water canals and toilet drains of leading hotels in Sri Lanka leads to Bere Lake. More than the solid waste, waste water and human excreta had polluted canals. Water occurs due to the presence of dissolved inorganic materials, organic materials such as proteins, fats, carbohydrates and other substance found in domestic and industrial waste water.