The iron pillar of Delhi is a metal structure 7.21 metres (23 feet 8 inches) high with a 41-centimetre (16 in) diameter that was constructed by Chandragupta II (reigned c. 375–415 CE), and now stands in the Qutb complex at Mehrauli in Delhi, India.
The metals used in its construction have a rust-resistant composition. The pillar weighs more than six tonnes and is thought to have been erected elsewhere, possibly outside the Udayagiri Caves, and moved to its present location by Anangpal Tomar in the 11th century.
Contents
Physical description
The height of the pillar, from the top to the bottom of its base, is 7.21 m (23 ft 8 in), 1.12 m (3 ft 8 in) of which is below ground. Its bell pattern capital is 306 mm (12 in). It is estimated to weigh more than six tonnes (13,000 lb).
The pillar has attracted the attention of archaeologists and materials scientists because of its high resistance to corrosion and has been called a "testimony to the high level of skill achieved by the ancient Indian iron smiths in the extraction and processing of iron". The corrosion resistance results from an even layer of crystalline iron(III) hydrogen phosphate hydrate forming on the high-phosphorus-content iron, which serves to protect it from the effects of the Delhi climate.
Inscriptions
The pillar carries a number of inscriptions of different dates.
Inscription of King Chandra or Chandragupta II
The oldest inscription on the pillar is that of a king named Chandra (IAST: Candra), generally identified as the Gupta emperor Chandragupta II.
The inscription covers an area of 2′9.5″× 10.5″(65.09 cm x 26.67 cm). The ancient writing is preserved well because of the corrosion-resistant iron on which it is engraved. However, during the engraving process, iron appears to have closed up over some of the strokes, making some of the letters imperfect.
It contains verses composed in Sanskrit language, in shardulvikridita metre. It is written in the eastern variety of the Gupta script. The letters vary from 0.3″ to 0.5″ in size, and resemble closely to the letters on the Allahabad Pillar inscription of Samudragupta. However, it had distinctive mātrās (diacritics), similar to the ones in the Bilsad inscription of Kumaragupta I. While the edges of the characters on the Allahabad inscription are more curved, the ones on the Delhi inscription have more straight edges. This can be attributed to the fact that the Prayagraj inscription was inscribed on softer sandstone, while the Delhi inscription is engraved on the harder material (iron).
The text has some unusual deviations from the standard Sanskrit spelling, such as:
pranśu instead of praṃśu: the use of dental nasal instead of anusvāra
mūrtyā instead of mūrttyā: omission of the second t
kīrtyā instead of kīrttyā: omission of the second t
śattru instead of śatru (enemy): an extra t
In 1831, the East India Company officer William Elliott made a facsimile of the inscription. Based on this facsimile, in 1834, James Prinsep published a lithograph in the Journal of the Royal Asiatic Society of Great Britain and Ireland. However, this lithograph did not represent every word of the inscription correctly. Some years later, British engineer T. S. Burt made an ink impression of the inscription. Based on this, in 1838, Prinsep published an improved lithograph in the same journal, with his reading of the script and translation of the text.
Samvat 1109 inscription
One short inscription on the pillar is associated with the Tomara king Anangpal, although it is hard to decipher. Alexander Cunningham (1862–63) read the inscription as follows:
Samvat Dihali 1109 Ang Pāl bahiTranslation:In Samvat 1109 [1052 CE], Ang [Anang] Pāl peopled Dilli
Based on this reading, Cunningham theorized that Anangpal had moved the pillar to its current location while establishing the city of Delhi. However, his reading has been contested by the later scholars. Buddha Rashmi Mani (1997) read it as follows:
Samvat Kinllī 1109 Aṅgapāla bādiTranslation: Anangpal tightened the nail [iron pillar] in Samvat 1109
History of the Iron Pillar
The pillar was installed as a trophy in building the Quwwat-ul-Islam mosque and the Qutb complex by Sultan Iltutmish in the 13th century. Its original location, whether on the site itself or from elsewhere, is debated.
According to the inscription of king Chandra, the pillar was erected at Vishnupadagiri (Vishnupada). J. F. Fleet (1898) identified this place with Mathura, because of its proximity to Delhi (the find spot of the inscription) and the city's reputation as a Vaishnavite pilgrimage centre. However, archaeological evidence indicates that during the Gupta period, Mathura was a major centre of Buddhism, although Vaishnavism may have existed there. Moreover, Mathura lies in plains, and only contains some small hillocks and mounds: there is no true giri (hill) in Mathura.
Based on paleographic similarity to the dated inscriptions from Udayagiri, the Gupta-era iconography, analysis of metallurgy and other evidence, Meera Dass and R. Balasubramaniam (2004) theorized that the iron pillar was originally erected at Udayagiri. According to them, the pillar, with a wheel or discus at the top, was originally located at the Udayagiri Caves. This conclusion was partly based on the fact that the inscription mentions Vishnupada-giri (IAST: Viṣṇupadagiri, meaning "hill with footprint of Viṣṇu"). This conclusion was endorsed and elaborated by Michael D. Willis in his The Archaeology of Hindu Ritual, published in 2009.
The key point in favour of placing the iron pillar at Udayagiri is that this site was closely associated with Chandragupta and the worship of Vishnu in the Gupta period. In addition, there are well-established traditions of mining and working iron in central India, documented particularly by the iron pillar at Dhar and local place names like Lohapura and Lohangī Pīr (see Vidisha). The king of Delhi, Iltutmish, is known to have attacked and sacked Vidisha in the thirteenth century and this would have given him an opportunity to remove the pillar as a trophy to Delhi, just as the Tughluq rulers brought Asokan pillars to Delhi in the 1300s.
It is not certain when the pillar was moved to Delhi from its original location. Alexander Cunningham attributed the relocation to the Tomara king Anangpal, based on the short pillar inscription ascribed to this king. Pasanaha Chariu, an 1132 CE Jain Apabhramsha text composed by Vibudh Shridhar, states that "the weight of his pillar caused the Lord of the Snakes to tremble". The identification of this pillar with the iron pillar lends support to the theory that the pillar was already in Delhi during Anangpal's reign.
Scientific analysis
The pillar was produced by the forge welding of pieces of wrought iron. In a report published in the journal Current Science, R. Balasubramaniam of IIT Kanpur explains how the pillar's resistance to corrosion is due to a passive protective film at the iron-rust interface. The presence of second-phase particles (slag and unreduced iron oxides) in the microstructure of the iron, that of high amounts of phosphorus in the metal, and the alternate wetting and drying existing under atmospheric conditions are the three main factors in the three-stage formation of that protective passive film.
Lepidocrocite and goethite are the first amorphous iron oxyhydroxides that appear upon oxidation of iron. High corrosion rates are initially observed. Then, an essential chemical reaction intervenes. Small secondary particles of slag and unreduced iron oxides in the iron microstructure alter the electrochemical behaviour and enrich the metal–scale interface with phosphorus. This indirectly promotes passivation of the iron (cessation of rusting activity).
The second-phase particles act as a cathode, and the metal itself serves as anode, for a mini-galvanic corrosion reaction during environment exposure. Part of the initial iron oxyhydroxides is also transformed into magnetite, which somewhat slows down the process of corrosion. The ongoing reduction of lepidocrocite and the diffusion of oxygen and complementary corrosion through the cracks and pores in the rust still contribute to the corrosion mechanism from atmospheric conditions.
The next main agent to intervene in protection from oxidation is phosphorus, which, like the chemical reaction described above, acts at the metal–scale interface. Phosphorus is enriched there by the same interaction between the slags and the metal. The ancient Indian smiths did not add lime to their furnaces.
In modern blast furnaces, the use of limestone yields pig iron that is later converted into steel; in this process, most phosphorus is carried away by the slag.
The absence of lime in the slag and the use of specific quantities of wood with high phosphorus content (for example, Cassia auriculata) during the smelting induces a higher phosphorus content (> 0.1%, average 0.25%) than in modern iron produced in blast furnaces (usually less than 0.05%).
Evidence of a cannonball strike
A significant indentation on the middle section of the pillar, approximately 4 m (13 ft) from the current courtyard ground level, has been shown to be the result of a cannonball fired at close range. The impact caused horizontal fissuring of the column in the area diametrically opposite to the indentation site, but the column itself remained intact. While no contemporaneous records, inscriptions, or documents describing the event are known to exist, historians generally agree that Nadir Shah is likely to have ordered the pillar's destruction during his invasion of Delhi in 1739, as he would have considered a Hindu temple monument undesirable within an Islamic mosque complex. Alternatively, he may have sought to dislodge the decorative top portion of the pillar in search of hidden precious stones or other items of value.
No additional damage attributable to cannon fire has been found on the pillar, suggesting that no further shots were taken. Historians have speculated that ricocheting fragments of the cannonball may have damaged the nearby Quwwat-ul-Islam mosque, which suffered damage to its southwestern portion during the same period, and the assault on the pillar might have been abandoned as a result.