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Iron in Ancient India c7.s5: Theory of Forging Iron Beams and Pillars

Iron in Ancient India c7.s5

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English

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Theory of Forging Iron Beams and Pillars

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It has already been stated that Dr. Percy, Dr. Murray and Sir Robert Hadfield found the Delhi pillar to be made of wrought iron. The iron beams of Orissa have also been found to be made of the same species of iron. These beams and pillars must then have been constructed by forging large quantities of wrought iron. The question now is—have these beams and pillars been forged as single columns or that short pieces of wrought iron have been forged and then welded? Experts are unanimously of opinion that such an enormous mass of iron as the Delhi pillar can even in these days of steam-rollers and hammers be with very grea difficulty forged. The conclusion therefore naturally arises that these beams and pillars must have been constructed by welding short pieces of wrought iron and not as entire columns. Direct evidence on this point is forthcoming, though it still reflects the greatest credit on the old Hindu metallurgists who could have successfully carried on the welding operations so very skilfully as to be scarcely perceptible.

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Writing about the beams in Konarak, H. G. Graves points out: ² "One beam, which is now lying on the portico, has evidently been partially exposed for a long period to the sandy winds, for it is worn down at least an inch in depth, enabling the defective structure to be seen. This particular beam and the fractured ends show very clearly that the method of manufacture was by welding up small blooms, generally about 3 or 4 lbs. in weight. The blooms are commonly 2 by 1 inch in section, but occasionally 2 by 2 inches or 1 by 1 inch, and a common length is about 6 inches. In a few cases the blooms may have been larger or the welding was done more effectively. The rough sketches appended to this paper show with fair accuracy the relative sizes and disposition of the blooms in several beams. Many of the broken ends show the existence of irregular and sometimes uniform cavities. It is possible to thrust a stick down some of them to a depth of 7 or 8 feet, and the sand-blasted specimen shows a cavity nearly the whole length of the beam. From these hollows, bits of cinder can be raked out." The blooms were probably welded together into short bars which were then in turn welded into big beams. Mr. Graves say that externally the beams are well finished though the cracks and lines show where joints were (see plate No. 4).

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² Journal of the Iron and Steel Institute, 1912, No. 1, Vol. 85, p. 196.

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As regards the Delhi pillar, the forging in this case is much more perfect than that of the Orissan beams and hence difficult to detect. The Committee of the Iron and Steel Institute in 1872, however, made some special enquiries with regard to this pillar.¹ Lieutenant Spratt of the Royal Engineers, then stationed at Delhi, came to the conclusion after enquiry that "the iron of which the pillar is made seems to have been originally in blooms of about 80 lbs. weight each." Even as early as 1858 Mr. Charles Wood of Middlesburgh, who was in India at the time of the Mutiny, stated that he believed that the pillar was of wrought iron and that it had been made by welding small pieces into the end of a shaft or bar. In 1871 Mr. Robert Mallet had stated: "We are thus obliged to consider that this pillar is not a casting but a huge forging in .... wrought iron," while shortly afterwards Mr. G. M. Fraser contributed a long letter to the *Engineer*, Vol. xxxiii, pp. 19, 20, in which the fact is clearly expreseed that the pillar was made of malleable iron and produced by welding together successive lumps or *mootees* of wrought iron which had been produced in a primitive blast-furnace. Fergusson, Vincent Smith, Ganguli and others agree in subscribing to this theory. This theory receives an added confirmation from the existence of many holes at irregular intervals in the Dhar pillar into which crowbars have evidently been put in order to help welding. Though at first sight the almost perfect finish of the exterior, specially of the Delhi pillar, negatives the hypothesis of forging small pieces into one whole, but when we judge of the almost unsurmountable practical difficulties of forging an *entire* piece of wrought iron as the Delhi or Dhar pillar appears to be, the author, at any rate, cannot but subscribe to the view that the method of forging the Delhi, Dhar, and Mount Abu pillars, as well as the gigantic Orissan beams, is unmistakably the same, viz. the method of welding short pieces into entire pillars and beams.

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¹ Ibid., 1872, Vol. II, p. 156.

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EXPLANATION OF "CORROSION RESISTANCE" POWER OF INDIAN IRON.

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(a) *Low manganese with low sulphur and high phosphorus.*

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Surprise has not unreasonably been expressed at the fact that the iron pillar at Delhi and other ancient specimens of iron have not rusted in a marked degree. General Cunningham offered a curious explanation of this fact by supposing that the oil of the bodies of the pilgrims who visit the Delhi pillar and embrace it as a mark of merit keeps it immune from rusting, but the learned General does not seem to have explained how the capital of the pillar, which is too high for human embrace, could be preserved in the way it has been preserved. The Delhi pillar is the best preserved of all the pillars. Mr. Graves points out that some of the Konarak beams were so heavily rusted that flakes half a foot square and half an inch thick could be scaled off. Most of them, however, were only superficially rusted and the rusting is mainly due to the beams remaining underground for two or more centuries. The iron clamps found at Bodh-Gaya are also very heavily rusted. The specimens of Singalese iron examined by Sir Robert Hadfield were well preserved, though belonging to the fifth century A.D. Dr. A. S. Cushman¹ is disposed to be philosophically inclined when he says, and says perhaps rightly, that "chemical and physical examinations of such ancient specimens might point the way to practical improvement in our own age, for one criticism that was often passed on modern steels was that their tendency to corrode and disintegrate stood in direct ratio to the rapidity with which they were manufactured ....... It seems to be a law of Nature that her materials should respond to the manipulations of the hands of man, and acquire properties that machinery cannot give." Be that as it may, two explanations are possible of this remarkable power of ancient specimens of iron of resisting corrosion—either there was something in the composition of the iron or that the beams were painted, or both. To the author it appears that both the factors have operated in enabling the Indian iron pillars and beams to withstand the corroding influence of wind and rain. In the first place the one point remarkable regarding the composition of the Delhi iron, Singhalese iron and other specimens of ancient iron is that all these specimens of iron are *free* from manganese and sulphur and contain a *tolerably high percentage of phosphorus*. The author agrees with Dr. Cushman when he suggests that probably "low manganese with low sulphur and high phosphorus would lead to high corrosion resistance" in iron.

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¹ Ibid., 1812, No. 1, p. 177.

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Dr. Cushman gives an analysis of an iron nail made in Virginia more than one hundred years ago. It was remarkably well preserved and contained, like old Indian iron, "low manganese with low sulphur and high phosphorus." The analysis was as follows:—

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| | Per cent. |
| Sulphur | ·013 |
| Manganese | ·06 |
| Carbon | ·03 |
| Phosphorus | ·205 |
| Silicon | ·121 |
| Copper | ·027 |
| Oxygen | ·15 |

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Professor Henri Le Chatelier was also struck by the almost complete absence, both of manganese and of carbon, which always occurred in noteworthy proportions in steels made by melting processes and also by the relatively high percentage of phosphorus. He also suggested that it was perhaps to the concurrence of these three factors that the exceptional durability of ancient Hindoo irons was to be attributed.¹

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¹ Journal of the Iron and Steel Institute 1912, p. 180.

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The author, however, is not aware of any experiments undertaken to confirm this theory and would take this opportunity of inviting chemists interested in the question of corrosion of iron to make further experiments on the subject.

(b) Application of paints on iron beams and pillars

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Besides the question of the composition of Indian iron the author has a suspicion in his mind that the pillars and beams were originally *painted*. Direct evidence on this point is also forthcoming, as Abul Fazal in the 16th century saw the beams at Puri painted.² The peculiar colour of the iron, specially at the top portion of the Delhi pillar, which misled early observers into thinking that the pillar was made of copper or bronze, might have been due to some kind of paint used for painting the pillar. The author has found out two formulæ of such paints used for hardening as well as preserving iron instruments in *Sārangadhar Padhati*, a compendium on miscellaneous subjects of the 14th century by the alchemist Sārangdhar. The first formula is briefly the following: "Grind together *pippali* (piper longum), rock salt and *kushta* wood (costus speciosus or saussurea Lappa) in cow's urine and cover the iron instrument with the mixture thus obtained. On now heating the instrument in the fire and then quenching in oil the instrument will be of superior quality."³ The second formula runs thus: "Grind together the five kinds of salt, mustard and honey and after painting the instrument with the mixture heat in the fire until at "yellow heat" its colour becomes blue like that of the throat of a peacock. The instrument would, on quenching in cold water, be quite good."⁴ Such an instrument will become extremely hard, so much so that "it will penetrate through the hardest armour as if through leaves of trees."¹ These two formulæ bring out two facts of importance. In the first place it is known as an undoubted fact that in the 14th century at any rate the Hindus were quite familiar with the process of hardening iron by quenching hot iron either in oil or water, and in the second place iron, at least iron instruments, were painted with a mixture containing salt and other ingredients and then heated in the furnace. The exact chemical action that takes place is difficult to understand. At first chlorides of iron are produced which perhaps on heating decompose, leaving a coating of the oxides of iron. It is possible that the Delhi and other pillars and beams were painted with a similar mixture and then heated in the fire, the process being continued, possibly with alterations, from early times down to the fourteenth century.

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² Ganguli's *Orissa and her Remains*, p. 262.

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³ पिप्पलीवेच्यो कुष्ठं गोमूत्रेण तु पेषयेत् ।

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⁴ अनेन लेपयेल्लोहं ततो चाग्नौ प्रतापयेत् । ततो निम्मज्जितं तेले लोहं तच्च विशिष्यते ॥ पञ्चभिर्लवणैः पिष्टं मधुभिस्तैः ससर्पपैः । रभिः प्रलेप्यल्लोहं ततो चाग्नौ प्रतापयेत् ॥

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¹ Annanda K. Kumarswami, Medieval Singhalese Art, p. 200.

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Dr. Kumarswami gives a somewhat different formula used for a long time in Ceylon and even now to give a 'blued' colour to iron articles and also to prevent rusting. The formula runs thus: "Take two parts of alum, one part of copperas, two parts of the leaves of *oxalis corniculata* and grind together and allow to stand three days; add the juice of one lime and spread over the iron to be coloured; place carefully in the fire until the right colour is attained."² Dr. Kumarswami explains the chemical action by supposing that "apparently the oxalic or other organic acid in the preparation reduces any higher oxide of iron to the ferrous state, and when applied to the steel and heated, slight etching takes place and a probable reduction of part of the sulphate to sulphide of iron. The temperature employed would affect the amount of reduction and oxidation. The blue colour is probably due to the uneven distribution of oxide and sulphide of iron."

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Moreover in the *Ayeen Akbari* we find that during the Moghul times iron guns when completed were painted with colour paints, and called 'rangin' (coloured).³

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³ Ayeen Akbari, Gladwin's Translation, Vol. I, p. 112.

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निक्षिप्यौषधं तत्रपोतं तस्योषधम् । ततस्तु विमलं तोयं पाययेच्छस्त्रमुत्तमम् । येन दुर्भेदशस्त्राणि भेद्येत्तु सबपर्वतम् ।

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COMPOUNDS OF IRON.

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(a) *Oxides of iron.*

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Of the compounds of iron the oxides of iron and the sulphide were artificially prepared and used in the Hindu system of medicine. The chloride of iron was also probably known but seldom used. The Buddhist alchemist Nāgārjuna (second century A.D.) is universally credited as the discoverer of the process of "killing" metals and specially iron. For example Chakrapāni (eleventh century) in describing the process of killing iron says: "I shall now describe the science of iron as promulgated by the sage Nāgārjuna." The author of *Rasendra-Chintāmani* also does the same.¹

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¹ नागाजुनो मुनीन्द्रः शशास मलोपशमनमित्यचनम् । तस्यानुकृतये वयंने तदिमदाचरैर्युमः ।

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The first notice of 'killing' iron and other metals (gold, silver, lead, copper and tin) occurs in the *Uttartantra* or supplement of the *Sushruta*, which is said by the commentator Dalhana to have been added by Nāgārjuna, who is also the redactor of *Sushruta*. In it we find the process called *ayashriti-bidhi* of iron and other metals in which "thin leaves of iron are to be smeared with the levigated powder of 'the salts' and heated in the fire of the cow-dung cakes and then plunged into a decoction of the myrobalans and assafœtida. This process is to be repeated sixteen times. The leaves are then to be ignited in the fire of the wood of *mimosa catechu* (khadira) and afterwards finely powdered and passed through linen of fine texture. The above process is equally applicable to the roasting of the other metals."²

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² तोच्छलोचपत्राणि तमुनि लवणवगेप्रदिग्धानि गोमय्याग्निप्रतप्तानि विफलाम्लसारा- दिकषायेध निष्वांपयेत् षोडशवारान् ततः खदिराङ्गारतप्तान्युपशम्यतप्तानि सूक्ष्मचूर्णानि कारयेत् । ...... एतेन सर्वलोहेषु अयस्कृतयो व्याख्याताः । सुश्रुत, चिकित्सास्थान ।

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Chakrapāni (eleventh century) gives an elaborate account of Nāgārjuna's process which may be summarised thus: "a bar of iron is to be rubbed with the levigated powder of the following vegetable products among others: the belleric myrobalans, *clitoria ternatea*, *vitis quadrangularis*, *boharhaavia diffusa* and *verbesina calend*. It is then strongly heated to the fusing point and plunged into the decoction of the myrobalans. The iron is then powdered by being beaten with an iron hammer. The powder is then digested in the decoction of the myrobalans and roasted repeatedly in a crucible.” *Rasendra-chintamani* (thirteenth century) gives the same account of Nāgārjuna’s recipie. *Rasendra-shār-samgraha* (fourteenth century) gives an elaborate account of the process of killing iron which is given below. *Kānta* (wrought) iron, being the best of all kinds of iron, has been recommended by all authorities as best suited for the purpose of “killing.” *Rasendra-shār-samgraha* writes:—

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When the proper kind of iron is selected, it is first finely powdered and then purified (शोधन) by macerating it in a decoction of the “three myrobalans” (त्रिफला). The iron is then again immersed in the same decoction and dried again in the sun. This process is to be repeated seven times. This is called “bhānu-pāka-bidhi” (भानुपाकविधि). The iron is next boiled in decoctions of various substances depending on the nature of the disease for which it is to be used. This process is called “sthāli-pāka-bidhi” (स्थालीपाकविधि). The iron thus treated is now washed in clear water and roasted inside two earthenware concave dishes with their mouths placed on each other and luted with mud. This pair of dishes is then put in a pit of suitable dimensions dug in the earth and heated by means of burning cowdung-cakes. This process is called “puta-pāka-bidhi” (पुटपाकविधि). The iron is then to be roasted ten, hundred or even thousand times, and it is believed that the greater number of “putas” iron has been subjected to, its medicinal efficacy increases in a corresponding degree. The alternate maceration and heating make the powder very light, and, in fact, the test prescribed by *Rasendra-shār-samgraha* by means of which the proper number of putas is to be judged is the extreme lightness of the powder. “The iron is to be roasted until being finely powdered and thrown on water, it will swim like a duck on account of its lightness.” 1

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It would interest readers to learn the methods of preparation

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वाजाकषाय विशेयः दशादिगतपाचकाः ।
तानदेव पुनस् तोयं यावच्चूर्णीकृतं कले ।
निस्तारन्ते जलेनैव समुत्तरति पंकवत् ॥

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of killed iron by modern Aurvedic physicians. As most Aurvedic physicians prepare their own medicines, the method of preparing the same medicine varies considerably. So far as we have been able to collect information, there are three different methods of preparing "lauhas."

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(1) Some physicians procure the best kind of iron, heat it in a blacksmith's forge and take the rust formed on the surface of the iron.

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(2) Others keep steel immersed in cow's urine for years together and take the rust collected on the surface.

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(3) While some are reported to prepare their "lauhas" by repeatedly heating powdered ferrous sulphate (क्षीरकास). Of course the method given in Chakrapāni, Rasendra-shār-samgraha and other works is followed by many orthodox physicians. In the methods Nos. (1) and (2) the rusts obtained are purified in the usual way, and then formed into balls with cow's urine or a decoction of the "three myrobalans," dried in the sun and calcined in the pit by means of burning cow-dung cakes in the usual way. The balling, powdering and calcining in an enclosed space are repeated ten, hundred or thousand times.

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We collected "lauhas" which have undergone different number of "putas" for analysis. The colour of these samples varied from greyish black and grey to orange-red. It was observed that one "puta lauha" was greatly attracted by a magnet, "lauha" which has been calcined ten times was attracted to a less degree, while a sample of seventy-eight "puta lauha" was very slightly attracted. As regards iron which has been calcined hundred or thousand times, it was not in the least attracted by a magnet.

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Qualitative analysis¹ showed the presence of a small quantity of soluble salt mostly potassium phosphate, siliceous matter and iron. There was no carbon (as we expected), nor any aluminium. The "one-puta," "ten-puta" and "seventy-eight-puta" "lauhas" are the products of heating the same sample of iron. The "hundred-puta" and "thousand-puta" "lauhas," both marked (A), are again the oxidation products of another sample of iron. Lastly, the "thousand-puta" "lauha," marked (B), is a different preparation.

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¹ The process of "killing" iron and analysis of "killed" iron have been reproduced here from a paper by the author and Mr. Birendra Bhusan Adhicari, Journal of the Asiatic Society of Bengal, 1910, 385.

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| "One-puta lauha." | | "Ten-puta lauha." | |
| Fe (5 c.c. H. only) | = ·012 | Fe | = nil. |
| Feo | = 68·1 | Feo | = 23·1 |
| Fe₂O₃ | = 20·4 | Fe₂O₃ | = 40·0 |
| Siliceous matter | = 10·1 | Siliceous matter | = 32·1 |
| Soluble salt (mostly pot. phos.) | = 1·3 | Soluble salt | = 4·6 |
| | 99·912 | | 99·8 mm. |

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| "Seventy-eight puta lauha." | | "Hundred-puta lauha." (A) | |
| Fe | = nil. | Fe | = nil. |
| Feo | = 9·5 | Feo | = nil. |
| Fe₂O₃ | = 51·2 | Fe₂O₃ | = 83·9 |
| Siliceous matter | = 34·1 | Siliceous matter | = 12·7 |
| Soluble salt | = 5·4 | Soluble salt (of which P₂O₅=·9) | = 3·7 |
| | 100·2 | | 100·3 |

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| "Thousand-puta lauha." (A) | | "Thousand-puta lauha." (B) | |
| Fe | = nil. | Fe | = nil. |
| Feo | = nil. | Feo | = nil. |
| Fe₂O₃ | = 78·1 | Fe₂O₃ | = 84·9 |
| Siliceous matter | = 17·9 | Siliceous matter | = 11·3 |
| Soluble salt | = 4·1 | Soluble salt (of which P₂O₅=1·2) | = 3·8 |
| | 100·1 | | 99·7 |

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From the results of analysis given above it is clear that the magnetic properties of the samples of iron which have undergone a fewer number of "putas" are not due to free iron, which is present in minute quantities in the "one-puta" "lauha" but to ferroso-ferric oxides, the ferrous and ferric oxides being present in them in varying proportions.¹

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¹ Of Roscoe and Schorlemmer's " Treatise on Chemistry," Vol. II, Part 2, " Magnetic oxide of iron ";—" when iron is heated to redness in the air, it becomes coated with iron scale. This is a mixture or a compound of the monoxide and sesquioxide in varying proportions. The inner layer which is blackish grey, porous, brittle, and attracted by the magnet, has the composition 6 Feo Fe₂O₃ and is not magnetic. The outer layer contains a larger quantity of ferric oxide, is of a reddish colour and is more strongly attracted by the magnet than the inner portion."

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As the number of " putas " increases, the amount of ferrous oxide diminishes, and at hundred " putas," and above, the iron is wholly present in the form of ferric oxide. Hence " hundred-puta " and " thousand-puta " " lauhas " are not attracted by the magnet.

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2. Siliceous matter is present in very large proportion varying from 10·1 to as much as 34·1 per cent. This impurity comes, as was subsequently ascertained, from the stone plates (खल्ल) on which the iron is powdered many times.

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3. " Shata-puta," " Sahasra-puta," " lauhas " have almost identical composition. Both are impure ferric oxide, the percentage of which varies from 78·1 to 84·6. Both are non-magnetic and " swim like duck " on water. On account of the very large number of " putas " in the course of which it undergoes maceration, powdering and roasting for a thousand times, the " shahasra puta " " lauha " is lighter and finer than " shata-puta." The time taken to prepare these lauhas is very long indeed. If one " puta " be finished in one day, the preparation of " shata-puta " takes more than three months, and that of " shahasra-puta " about three years. As the roasting is carried on in closed vessels the oxidation proceeds very slowly. If, however, open vessels be employed in future the time may be greatly curtailed.

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4. The test of " swimming on water like a duck " is a crucial one with the Aurvedic physician for " lauhas." We have seen that precipitated ferric oxide of the laboratory does not " swim like a duck." It is probable that Aurvedic " lauhas," being very light and porous, are easily assimilated in the body while ordinary ferric oxide being not so light and porous is not easily taken up and hence not used by Allopathic doctors.

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