History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c12: Chapter Ii. Indus Valley Civilization

History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c12

Language: English

c12.s1 Table Iii — 14 parts
c12.s2 Dyeing — 2 parts

Chapter Ii. Indus Valley Civilization

A prehistoric settlement of a different type from those of the more or less self-contained little peasant communities of Baluchistan and the neighbouring regions of Sind developed itself since 2500 B. C. on the flood plains of the Indus (Sind) and its five tributaries (the Punjab). This was symbolized by populous cities, highly skilled industries, extensive commerce with river communications; a pictographic script and definite standards of weights and measures, as revealed by excavations at Mohenjo-daro in Sind and Harappa in the Punjab. It embraced a vast territory extending from the Makran coast to Kathiawar, bounded on the west by the mountains of Baluchistan and Waziristan, on the north by the Himalayan Hills and on the east by the Thar desert (*cf.* Fig. 5). The recent exploration in the valleys of the rivers Saraswati and Drishadwati in Bikanir by A. Ghosh of the Archæological Department of India shows that Harappan Civilization extended further east beyond the Thar desert into Rajputana. The pottery specimens, as well as the copper and bronze objects, found here resemble closely those of the Harappan Culture. This is also supported by the excavations of painted grey wares in an ideal setting and sequence at Hastinapur near Meerut in 1951-52. It represented a civilization as uniform as that of Sumer in Mesopotamia and of the Nile Valley in Egypt. Some forty different settlement sites with two great citadel cities at Harappa and Mohenjo-daro have already been disinterred. Findings of the excavations demonstrate a surprising uniformity in the construction and technique of its pottery vessels produced on a mass scale, in its houses built of baked bricks of standard dimensions, and in the stamp seals with an yet undeciphered uniform script. Some of the settlement sites are villages and the others appear to be small towns with the two large citadel cities of Harappa and Mohenjo-daro as twin capitals. The entire settlement area can be viewed, in the opinion of some archaeologists, as representing a vast kingdom or empire of the early Bronze Age in India (Fig. 5). The civilization that was evolved here is known as the Indus Valley Civilization or Harappan Culture. It is believed to be allied to the Sumerian and Egyptian Cultures, and there are evidences of contact and trade exchanges between the people of the Indus Valley and those of Sumer and Egypt. Archæological finds in and around the two citadel cities show an absolute uniformity in their articles, well-planned streets, magnificent systems of drains regularly cleared out, commodious two storied houses of baked bricks, granaries of large size, public baths, pillared halls, etc. They suggest, as Piggott concludes, a highly efficient centralized government by a divine monarch or a small priestly caste, and a regular local municipal administration. Monotonous rows of miserable mud-brick tenements outside the city walls suggest quarters for labourers or artisans. According to the opinion of some competent authorities, Harappa and Mohenjo-daro are the twin capitals of one and the same kingdom linked by a continuous river thoroughfare and controlled by a common authority having a dual seat of government.

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The sites of both the cities are laid out on a common ground plan with a rectangular impressive citadel on an artificial platform about 30 ft. high with strong defensive walls. The citadel contains public and ceremonial buildings and processional terraces. Below the citadel are the streets and houses of the town and the industrial quarters for the labourers (Fig. 6).

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The essential characters of the cities and their rulers are thus described by Wheeler in *Ancient India*, No 3, 1947:

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“Whatever the source of their authority—and a dominant religious element may fairly be assumed—the lords of Harappa administered their city in a fashion not remote from that of the priest-kings or governors of Sumer and Akkad In Sumer, the wealth and discipline of city-state were vested in their chief

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SITE PLAN OF MOHENJO-DARO SITE PLAN OF HARAPPA

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Fig. 6. ( Piggot, *Prehistoric India*, 1950 )

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deity, i. e. in the priest-hood or a priest-king. The civic focus was the exalted temple, centre of an elaborate and carefully ordered secular administration under divine sanction. In essence, the picture is one of a rigid and highly evolved bureaucratic machine, capable of organizing and distributing surplus wealth and defending it, but little conducive to the political liberty of the individual.”

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The archæological evidences, according to Wheeler, Piggott and others, therefore, suggest that the Indus Valley Civilization was evolved in a state ruled over by priest-kings from two main seats of government—the two capital cities of Harappa and Mohenjo-daro—linked by a great navigable river, Indus, with its five tributaries, which formed the main artery of communication between them. These priest-kings seemed to exercise an absolute and autocratic power. From this it follows that there should have existed an organised system of peasantry to produce food for the large population of these cities and of smaller towns of the kingdom. Of this, however, there is little direct evidence. Curiously enough, there is also no evidence of large temples or palaces. This seems to imply that worshipping in household shrines rather than congregational religious rites in temples was the system in vogue. Many features of the Harappan religious rites and worship are still retained in the Hindu society as their derivation from the Aryan traditions cannot be easily accounted for. The people who had developed this Indus Valley Civilization, it is believed, were of mixed origin and diverse types though there is still some controversy about it.

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An idea of the knowledge of chemistry, acquired by the Indus Valley people, can be obtained from a consideration of the pottery vessels, articles of faience, beads, metallic objects, etc. that have been brought to light as a result of the excavations. These will now be discussed in somewhat greater details.

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Indus Valley Pottery

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We shall consider the pottery first. The pottery of the Indus Valley sites is for the most part plain; produced on a mass scale on a rapidly spinning potter’s wheel, for purely utilitarian purposes. It has got a particular type of characteristic of its own. This generally consists of a platter on a raised foot; usually described as an “offering stand”. Potters’ kilns have also been found within the residential areas of the city of Mohenjo-daro at its latest phase. These are circular in shape. The stoke-hole and furnace lie beneath a perforated floor, originally covered by a domed roof. Decorated and painted potteries were also made by the Harappan workers. These contain black designs painted on a deep red, lustrous slip The wares are of black-on-red type reminding strongly of a connection with the North Baluchistan wares—and also show striking similarities with the Kulli style painting of the South Baluchistan wares Some true polychrome potteries of exceptional variety have been found at Harappa and Mohenjo-daro These are painted in red and green on a buff slip and are possibly related to the polychrome wares of the Nal Culture of South Baluchistan *Cf* Fig. 7 (*a*, *b*, *c* and *d*) and Fig 8 (*a* and *b*)

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The commonest wares manufactured on a large scale were, however, bricks, water-pots, vessels and jars. Bricks are all well-fired with a uniform size measuring normally 11 by 5.5 by 2.5 inches. Huge earthenware wheel-made jars, three feet in height, used probably for storing water or grain, have been found at Mohenjo-daro and Harappa

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Faience is another important variety of pottery produced by the Indus Valley people. It is a vitreous substance with a glazed surface often coloured by the addition of suitable mineral matters, produced by firing a composition of some base mixed with a powdered glaze. This suggests contact with Mesopotamia where faience beads were quite common in those early days

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The pottery wares, both plain and decorated, were made of a good variety of clay that burned pink or light red in colour Sometimes, however, a clay was used which burned gray. This clay might have been imported, though the wares were of local manufacture. It required little or no tempering.

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Fig. 7a.

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Fig. 7b

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Potteries from Harappa (Vats, *Excavations* *at Harappa*, 1940).

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(b) CEMETRY H FLASKS, ETC., MOSTLY OF STRATUM II. Fig. 7c. Potteries from Harappa ( Vats, *Excavations at Harappa*, 1940 ).

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Fig. 7d. Potteries from Harappa (Vats, *Excavations at Harappa*, 1940).

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Fig. 8a. Painted potteries from Harappa (Piggot, *Prehistoric India*, 1950).

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Fig. 8b Painted potteries from Harappa (Piggot, *Prehistoric India*, 1950).

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A third variety of clay used at Mohenjo-daro produced a ware of very light pink colour and was of an exceptionally compact texture.

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The tempering materials used with clay were mica, sand and lime. These were often used singly and rarely in combination. Mica is a very common substance found in the pottery wares as it betrays itself by its lustre. It is a common ingredient in the sand of the Indus Valley, from which it can be readily obtained by levigation. Its presence in clay facilitates the working of the latter on the wheel, and the drying of the pottery piece without cracking It, therefore, served as a useful tempering material. Lime is present in the fabric of both small and large Harappan jars Curiously enough it has been found to occur often in lumps of quite appreciable sizes. In fact, extra large fragments of lime have been flaked off the surface of some of the jars through the swelling due to slaking. These large particles of lime, in the opinion of Mackay, were mixed up with clay accidentally from the floor at the time of making the pots. A similar use of lime as a tempering material has been found in the wares of ancient Baluchistan, in some of the wares of Al Ubaid, Jemdet Nasr and in many of the predynastic wares of Egypt Opinions may differ as to the value of lime as a tempering material But with certain clays it seems to be an important ingredient and from the earliest times it has been mixed with them for this purpose.

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The prevailing colours of the brick, pottery and miscellaneous terra-cotta objects found in such abundance at the Indus Valley sites are light red or salmon. Black or grey are rather rare. Sana Ullah (archæological chemist), in his analysis of these products, remarks that the colours are due to the presence of iron compounds in the clay, which develop a red shade in the oxidising atmosphere of the kiln, while black or grey products are obtained when a reducing or smoking atmosphere prevails in the course of burning. Analysis further shows that the slip of bright red colour sometimes found covering the pottery body is due to ferric oxide; and the black or chocolate designs, that are found painted on the body, owe their colour to oxides of manganese. This establishes an identity of the colouring agents used by the Indus Valley people with those used to-day by the Indian potters. Much of the ancient technique seems to have been handed down to the present time without alteration. The potters in India today prepare the red slip by levigating red ochre or *Multani matti* (a yellow ochreous earth) with water. For black or chocolate shades he employs a manganiferous hæmatite. The manganese oxides, frequently associated with ferric oxide, give a pure black colour when rich in manganese; when the proportion of iron in the mixture preponderates, a chocolate colour develops

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A notable variety belonging to this colouring group is represented by a number of fine earthenware bangles usually black in colour, sometimes mottled white, but all characterised by the vitreous texture At Harappa, a dark red variety of earthenware bangles has been found. The chemical analysis of one of the specimens by Sana Ullah reveals .

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| Silica . . | 58.28 | per cent |
| Alumina . | 19.63 | „ |
| Ferric oxide .. | — | — |
| Ferrous oxide . | 8 70 | „ |
| Manganese oxide . | 0.13 | „ |
| Lime | 9.63 | „ |
| Magnesia . | 4.39 | „ |
| Alkalies . | 3.43 | „ |
| Copper oxide . | — | — |
| Water . . | — | — |

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The proportion of lime and magnesia are rather large. They account for the fusibility of the clay and vitreous body of the specimens. The black colour is due to ferrous oxide which also indicates the occurrence of a reducing atmosphere during the firing

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Chemical analysis of a few other ceramic materials found at Mohenjo-daro may be given here (Table 1).

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TABLE I

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| Specimen | Silica | Alumina | Ferric oxide | Ferrous oxide | Manganesc oxide | Lime | Magnesia | Alkalies | Copper oxide | Water | Analyst |
| Greenish pottery | 52.39 | 17.03 | — | 2 29 | — | 15.78 | 4 45 | 1 71 | — | 1 05 | Sana Ullah |
| Faience bangle | 88.12 | 3 02 | 1.82 | — | — | 1 26 | — | & Na₂O, 4.5 / & K₂O, 0.65 | 0 46 | — | " |
| Faience vase (bluish green) | 89 76 | 3.86 | — | — | — | 0.88 | trace | 4 07 | 0 50 | — | " |
| Faience (chocolate) | 91 07 | 2.44 | — | — | trace | 1 28 | trace | 2 08 | 1 98 (Cu₂O) | — | " |
| Steatite faience disc | 57.99 | 4.85 | — | — | — | 4 31 | 27.20 | 3.54 | 1.09 | 2.01 | Hamid |
| Steatite faience statuette | 57 23 | 3.69 | — | — | — | 6.39 | 28 99 | 1.88 | 0 46 | 1 36 | " |
| Slip from steatite seal | 61.2 | 2.40 | — | — | — | — | 34 60 | — | — | 1 8 | Sana Ullah |
| Steatite flat beads | 63 65 | — | — | — | — | — | 33 80 | — | — | 1.09 | " |

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The pottery articles of the Indus Valley are found to be all well-baked. The resulting fabric was hard enough to withstand considerable knocking about. The uniformity of the colour indicates that the potter had sufficient control over the heat of his furnace. Even in the case of larger storage jars often as much as 1·02 inches thick, this uniformity of colour was maintained right through. Very few over-heated vessels were noticed by Mackay among the findings, the number of under-fired ones was also rather small. Some few over-fired specimens have a greenish tinge due to the presence of ferrous compounds, in whose formation time plays an important part.

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Mackay reports of two curious pottery kilns found at Mohenjo-daro. Their diameter at the top measured some 3 ft. 3 in The flat base of one of the kilns was, however, 2 ft 10 in in diameter· the diameter of the base of the other was 3 ft. 2 in. But the depth of both the kilns was 4 ft 3 in. They were paved with brick and round the inside of each was a 4 inch ledge The top of the kilns was only slightly above the level of the door-sill on the side. The vitrification of the mud walls of these pits shows that they were used to fire articles at a high temperature. The fuel used was either wood or charcoal, the white ashes of which are still to be seen. The ledges mentioned above were probably intended for the support of a crucible or, if it be supposed that the kilns were used for glazing, a grating might have rested on the circular ledge. According to Mackay these kilns were probably used for objects more fusible than copper, because of their lack of draught or vent in the lower portions But there is no definite evidence about it (Fig. 9).

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At Harappa three types of furnaces have been found · (*a*) round, (*b*) cylindrical pits dug into the ground with or without brick lining, (*c*) pear-shaped pits also dug into the ground with or without brick lining. The brick-lined ones are plastered with mud mixed with sand. It appears that the firing was not uniform; varying degrees of heat were used with evidence of intense heat in some of the furnaces, provided by vitrification of the walls. Repeated mud-sand plastering gives an indication of repeated use.

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Fig. 9 Pottery kiln from Mohenjo-daro (Mackay).

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Glazed pottery found at Mohenjo-daro represents, according to Mackay, the earliest specimens in the world. In Egypt the practice of glazing started at a later date; in Mesopotamia the art appeared round about 1000 B. C. Faience was, however, extensively produced in the Indus Valley. It occurs frequently both in the higher as in the lower levels of the excavation.

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Being of opinion that the glazing of pottery is probably Indian in origin, Mackay writes:

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"It is certainly interesting to find that glazed pottery was used in India before it appears to have been known in Mesopotamia. And it should be noted that the quality of the Indian sherds that I have just described is equal in finish to any glazed ware of ancient Mesopotamia. The four pieces found at Mohenjo-daro are beyond all doubt the handiwork of a potter who was well acquainted with the process and able to carry it to a high degree of perfection".

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The microscopic examination of faience objects at Mohenjo-daro reveals a compact granular structure, composed of angular quartz grains They are bound together with a transparent cement. A chemical analysis of these objects also shows that silica is the chief constituent (Table I), forming about ninety per cent of the total amount. It may, therefore, be inferred that the composition of the original paste was finely crushed quartz or pure white sand, a glassy flux and, if necessary, a colouring matter. The moulded object had to be dried and fired in order to bring about the fusion of the flux Curiously enough, analysis shows absence of clay which might have given coherence and plasticity to the paste for working and moulding. It is suggested by some authorities that probably silicate of soda, which forms a highly viscous solution with water, was used as a constituent of the paste. This served to impart the desired property to the wet paste. The practice of preparing an alkaline silicate by the fusion of soda with sand was well known to the ancient peoples who practised the art of glazing. The hollow objects were possibly moulded on cores of sand, which was held in some fabric and raked out after firing. Impressions of the fabric as well as remains of the sandy core, have been detected in several specimens

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The white body is free from any metallic colouring matter and forms the basis for the coloured varieties. Analysis shows that those having blue and green shades contain copper oxide, which was added to the paste probably in the form of a natural ore. This also served to produce a chocolate coloured ware when heated in a reducing atmosphere of the kiln, due to the formation of cuprous oxide. The light red variety containing ferric oxide was probably produced by the addition of red ochre to the raw paste Most of the glazed pottery specimens have faded by weathering to a light blue or green colour. The granular white body material has been found, however, to often contain black specks. These may be the carbonized remains of an adhesive that was found necessary to hold the ingredients of the paste together before it was dipped in, or painted with the glaze.

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Apart from quartz as body material, both powdered and carved steatite were also used. Analysis of two such specimens has been recorded in Table I. Powdered steatite, however, does not seem to have been used in ancient Egypt for this purpose. It has been suggested that instead of adding any silicate to hold together the powdered steatite before firing, the object might have been extracted from its mould while still damp and, after being coated with the glaze, was heated in an increasing temperature until the fusing of the glaze bound the whole mass together.

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The practice of cutting objects from solid stone and then glazing them was frequent in Mohenjo-daro. It was common also in Egypt.

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Most of the glaze on the steatite objects found at Mohenjo-daro has disappeared by weathering and very few of them have been found unbroken and whole. They are generally of small size. Some of these were probably used for keeping cosmetics. On examining these articles it is found that the glaze has generally penetrated well into the body both on the inside and outside of the object. In a few cases it was also found that a certain amount of frit was mixed with the paste itself and was also applied to the ware both inside and outside. This undoubtedly strengthens the articles. We thus find that the Indus Valley potters generally used quartz and ground carved steatite as the body material for their glazed pottery.

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Seals

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Though these do not come correctly under the category of pottery, it might be convenient to discuss them here in connection with glazed wares.

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The seals found at Harappa and Mohenjo-daro are coated with a smooth glassy-looking substance, resembling a glaze. No colour was detected on any of these seals. The surface coating on one of these seals was analysed with the following results by Sana Ullah:

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| Silica | | . | 61.20 | per cent. |
| Oxides of aluminium and iron | . | . | 2.4 | " |
| Lime | ... | .. | — | — |
| Magnesia | ... | ... | 34.6 | " |

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The surface substance is steatite or talc The body and the coating of the seals are of the same material. But the coating might have been an applied one, as it scales off just like a slip.

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Perhaps before engraving a seal it was coated in order to conceal blemishes and then fired in a kiln like pottery-wares. The seals found cannot, therefore, be regarded as examples of glazed pottery.

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A vitreous paste seems to have been used for the glaze. Slabs of this material have been found at Harappa and Mohenjo-daro. It resembles glass in some respects, and shows a smooth fracture ; but it is opaque An analysis of this vitreous paste by Sana Ullah shows its composition as follows

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| Silica | 88.12 per cent. |
| Aluminium oxide | 3 12 " |
| Ferric oxide | 1.82 " |
| Lime | 1.26 " |
| Alkalies | 5.04 " |
| Cupric oxide | 0 46 " |

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The mixture was probably fired at about 1200°C

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Another slab of carnelian blue colour on analysis by Hamid (archæological chemist) gave the following results.

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Many other slabs of similar composition have been found. These were probably ground to powder like the modern enamels, and used for glazing purpose with the addition of a little soda to serve as a flux. In the case of steatite bodies, there must have been serious difficulties to make the resulting powder adhere properly to the surface of the body. It has been suggested that to overcome this, the powder might have been mixed with certain oils, which would volatilize at high temperatures leaving no trace behind: or, the slabs might have been heated to a semi-fluid state and then applied to the body of the material to be glazed, followed by a prolonged heating of the object in order to make the glaze flow freely over it. The layer of the glaze has, in fact, been found generally to be smooth and thin No evidence of over-firing has, however, been detected, which would produce a matt or pitted surface.

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In the case of a few other bodies, an impression of a canvas-like material has been found on the surface below the glaze. It is suggested that this served as a backing to hold together the ingredients of the paste constituting the body of the ware, preparatory to glazing. The canvas-like material was subsequently burnt away in the kiln. The glaze has, however, been found to penetrate well into the paste forming a hard but somewhat brittle material. It is also likely, as assumed by Sana Ullah, that the glazing was carried out in a second firing as at present. The prevailing colours of the faience glaze of the Indus Valley wares are bluish green or greenish blue, although indigo blue, apple green, maroon, black and colourless examples have been found. The blue shades owe their colour to copper oxide, while green contains iron oxide in addition. The black or dark maroon glaze contains an excess of manganese oxide.

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As a result of a careful examination of a number of specimens of glazed pottery Mackay has been able to throw a considerable amount of light regarding the methods employed in their preparation. Two pieces of sherds resemble very much copies of mosaic glass. But no true glass has yet been found either at Mohenjo-daro or at Harappa. Both of these are made of a light grey clay of medium thickness which is well baked and is tough. A certain amou white sand or quartz is present in the body as well and a certain amount of charcoal. A purplish black slip constitutes the dark wavy markings. The method of painting patterns seems to have been first coating the pottery pieces with this dark slip and then washing them so as to leave a wavy pattern. There is a parallel of this curious technique in a painted pottery sherd found at Kish by Watelin.

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We may now summarize about the pottery wares of the Indus Valley Civilization. Brown glazed pottery articles formed the most common variety. Some polychrome pottery objects, decorated with floral and geometric patterns in black and white, on a red ground, have been found. The base of some vases has a row of lotus petals as an adornment. Potteries in some cases were slip glazed, but mostly painted. Painted potteries were generally made by painting or decorating on a slip applied to the body. Slips used were also coloured buff, cream, pink and red. These were made mostly of ferruginous clays, or by mixing red ochre with clay. The articles were finally burnt. Manganiferous hæmatite was used for black colour, and gypsum for producing white pottery.

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Lime and Mortars

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The mortars used by the Indus Valley people consisted mainly of mud. But in the later periods gypsum cement of a light grey colour was employed for painting the walls of certain buildings at Mohenjo-daro. The gypsum used contains a considerable proportion of sand and clay, and a trace of calcium carbonate. A high percentage of lime has been found in an exceptionally well-constructed drain of the intermediate period at Mohenjo-daro. Analyses of certain samples of mortars collected from different spots and sites are given in Table II. It will be observed that these mortars were made generally of gypsum, lime and sand.

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TABLE II

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(Mortars)

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| Localities | Gypsum | Carbonate of lime | Sand | Alkaline salts | Moisture | Analyst |
| Wall | 74 12 | 2.50 | 20 41 | 1.18 | 1 79 | Sana Ullah |
| Do | 63 25 | 0 66 | 31.61 | 3 47 | 1 01 | " |
| Tank | 43.75 | 13 78 | 38 04 | 2 47 | 1.96 | " |
| Drain | 56.73 | 27 87 | 16 64 | — | 1 76 | " |
| Vat | nil | 69 58 | 21.71 | 5.44 | 3 27 | Hamid |
| Drain and cess pit | nil | 31.96 8.82 (magnesium carbonate) | 46.74 | 0.74 | 3 74 | Sana Ullah |
| Pointing of circular / platform. | 59.90 | 0.94 | | | | " |
| Concrete floor | trace | 37 63 2 18 (magnesium carbonate) | | | | " |
| Brick floor | nil | 26 50 34.80 (magnesium carbonate) | | | | " |

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Metal and its Working

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The urban civilization of the Indus Valley belongs formally to the Bronze Age, since copper and bronze were the only metals that were used for making tools and weapons. The findings at the Indus Valley sites prove that the metal workers of the two capital cities of Mohenjo-daro and Harappa were very skilful and had a plentiful supply of copper, silver and gold. Uses of lead and tin were not uncommon though the latter metal occurred always alloyed with copper in the form of bronze.

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Copper and bronze were most frequently used for domestic utensils, axe-heads or celts, for daggers, knives, lance-heads, arrow-heads and sickles (Fig. 10). They were also used for statuettes, bangles finger-rings, ear-rings, and amulets, as well as for wires and rods Bronze was preferred to copper for making weapons and implements with extra sharp cutting edges (Figs 11-*a*, *b* : 12-*a*, *b*). It contained, as the analysis shows, a high percentage of tin (approximately 10 per cent) added either accidentally or deliberately Tin and copper ores, which are often found together, give rise directly to bronze on smelting. An alloy of copper and arsenic ( 3-4.5 % ) was also used in place of bronze. The presence of arsenic might have been accidental, but it increased the hardness of the metal It might have been derived from the use of arsenical copper ores. Indus Valley copper has been found to contain normally a little nickel (usually below 0 5 per cent and seldom exceeding 1 per cent).

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Some representative analyses of copper and bronze articles found at Mohenjo-daro and Harappa are given below (Table III).

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A large hoard of copper and bronze implements contained in a copper pot securely covered by an inverted dish has been found at Harappa These on analysis were found to contain varying quantities of arsenic, nickel and lead.

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Fig. 10 Copper articles from Harappa (Vats, *Excavations at Harappa*, 1940).

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Fig. 11a. Copper and bronze articles from Harappa (Vats, *Excavations at Harappa*, 1940).

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Fig. 11b. Copper and bronze articles from Harappa (Vats, *Excavations at Harappa*, 1940).

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Fig. 12a. Copper and bronze objects from Mohenjodaro (Mackay, *Further Excavations at Mohenjodaro*, 1938).

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Fig. 12b Copper and bronze objects from Mohenjodaro (Mackay, *Further Excavations at Mohenjodaro*, 1938).

Table Iii

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| Specimen | Copper | Tin | Antimony | Arsenic | Iron | Nickel | Lead | Sulphur | Oxygen | Remarks | Analyst |
| Copper lump I | 96.67 | — | 0 88 | 0 15 | 0 03 | 1 27 | 0 02 | 0 18 | — | Unaltered | Sana Ullah |
| Copper lump II | 92 49 | 0.37 | trace | 1 30 | 1.51 | 1 06 | trace | 2 26 | 1 01 | Partly oxidized | " |
| Fragment of some implement | 95 80 | — | 0.72 | 0.74 | 0 12 | 0.25 | 1 58 | 0 61 | 0 18 | Unaltered | " |
| Copper chisel | 92 41 | — | 0 10 | 3 42 | 0.59 | 0 15 | 3 28 | 0 05 | — | " | " |
| Bronze button | 88 05 | 8 22 | 2 60 | trace | 0 29 | trace | — | 0 84 | — | " | " |
| Bronze slab | 82 71 | 13.21 | 0 33 | 1 17 | 0 42 | 0 56 | 0.11 | — | 1 49 | Partly oxidized | " |
| Copper object | 94 64 | 0 31 | 0 06 | 0.40 | 0 28 | 0 33 | 0 71 | 0 69 | 2 58 | " | Hamid |
| " | 97 23 | — | — | 0 24 | 0 29 | 0 89 | 0 81 | 0 10 | 0.44 | Slightly oxidized | " |
| Bronze object | 90 18 | 7 66 | 0 43 | — | 0 50 | 0 20 | 0 95 | 0 07 | — | Unaltered | " |
| " | 88.49 | 9 88 | 0 14 | — | 0 10 | 0.30 | 0 22 | 0 06 | 0 81, | Slightly oxidized | " |
| Spear head | 97 66 | — | — | 0 06 | 1 11 | 0 14 | 0 70 | — | — | Unaltered | Sana Ullah |
| Celt | 98 37 | 0 09 | — | 1 40 | 0 02 | 0.10 | 0 11 | — | — | " | " |
| Needle | 92 55 | 1 29 | — | 2 90 | 0 20 | 0 21 | 3 72 | — | — | " | " |
| Dagger | 91 00 | 6 76 | 0 44 | 0 04 | 0 74 | 0 14 | 0.58 | — | — | Completely oxidized | " |
| Chisel | 87 42 | 10 45 | — | 1 10 | 0 34 | 0.17 | 0 52 | — | — | Unaltered | " |

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Technique employed in the Indus Valley metallurgy included both casting and forging In the former process the metal had to be previously melted before being poured into a mould. Pure copper, when cast in a closed mould, becomes spongy due to the bubbles of free oxygen. But the addition of a very small percentage of tin or of arsenic acts as a deoxidizing agent. As most of the copper articles found at the Harappa and Mohenjo-daro sites contain these foreign metals in small amounts, their composition was quite suitable for production by casting But curiously enough the closed mould casting was never used for the production of tools in the Harappan Civilization. Most of the bronze objects were products of casting; some, however, had to be shaped and finished by hammering. This indicates that the Indus Valley metal-smiths were quite familiar with the properties of bronze-that enable it to be forged at a temperature just below redness The analysis of bronze objects reveals an advanced state of knowledge of bronze-making on the part of their makers. Copper and bronze vessels have been found together which supports the assumption that they were in simultaneous use. This was presumably due to the scarcity of tin. Copper alloyed with arsenic was also used at Mohenjo-daro and Harappa, as copper-arsenic alloy is comparable with low grade bronze in hardness. As already stated, this alloy might have resulted accidentally from the use of arsenical copper ores for the extraction of the metal. There are evidences that copper articles, such as axes, were made both by casting and hammering; the edges were usually hammered out after plain blades had been cast.

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Copper was possibly smelted from ores near the mines, the metal being afterwards refined in clay crucibles. A fragment of such a crucible with the slag sticking to the edges has been found at the excavation at Mohenjo-daro. From an examination of the analytical results, given above, of specimens of various articles found at the Indus Valley sites, it may be concluded that the people at that time were acquainted with four distinct varieties of copper and its alloys: viz. (a) crude copper, (*b*) refined copper, (*c*) copper-tin alloy or bronze and (*d*) copper-arsenic and copper-arsenic-lead alloys.

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(*a*) Crude copper, the first product of the smelting furnace, was too rich in sulphur to be worked up by hammering and was suitable only for casting heavy and plain objects.

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(*b*) Refined copper, on account of its purity and ductility, rendered it quite suitable for making vessels of elaborate shapes, as also for obtaining sound casting in closed moulds. The presence of small amounts of arsenic and antimony imparted appreciable hardness to the metal.

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(*c*) The percentage of tin in the bronze articles found at the Indus Valley sites lies between 4.51 to 13.21. Those with 11-13 per cent of tin are more common, although lower grades also occur to some extent. The presence of the high grade alloys well-suited for sharp-edged tools, with a fairly regular proportion of tin, leaves hardly any doubt that the addition of the white metal was intentional and not the result of mere accident. Tin was possibly imported from outside, likely from Persia. It is obvious that this stage in metallurgy had been reached after prolonged experimentation and experience with copper and its alloys with arsenic and tin. An appreciable amount of antimony and arsenic has been found in many bronze articles, which thereby gain an increased hardness.

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(*d*) Copper-arsenic alloy was employed as a substitute for low grade bronze. Presence of lead in copper and bronze tended to increase their fusibility, rendering the latter more suited for casting. But it was more probably an accidental impurity than an intentional addition. Copper ore is unknown in Sind. The nearest deposits are to be found in the countries bordering on the west of the Indus Valley. In Baluchistan rich copper ores occur at Shah Ballaul and at Robat. Here large heaps of copper slags have been found indicating ancient smelting at these sites. Perhaps the ores were mined and smelted here and then transported to the cities of Harappa and Mohenjo-daro. The evidence of the extraction of copper is still to be seen at the various village sites belonging to the Mohenjo-daro Period of history that have been uncovered in Baluchistan Deposits of copper ore also occur at Râs Kuk and the Kojak Amran range in Baluchistan In Afghanistan there are rich veins of copper in Shah Maksud range In Persia there are copper deposits at Anarek and in Kaleh Zeri (Kerman) At both these places there are evidences of extensive ancient workings The nearest copper mines in India proper are those in Rajputana These are situated near Ajmere in Sirohi, in the Mewar and Jaipur states especially those at Khetri and Singhana bear the evidence of having been worked from very early times In the copper lumps found at Mohenjo-daro the small quantities of sulphur indicate the use of the sulphide ore, which abounds in these mines, for the extraction of copper. The presence of lead in some of the copper objects is also noteworthy Copper ores associated with lead occur in Rajputana and in the Hazaribagh district, as also in Afghanistan and Baluchistan. Samples of copper ores from Khetri, Alwar, Singhbhum and Afghanistan contain both nickel and arsenic, while those from Bilaspur and Nellore are entirely free from nickel It can, therefore, be concluded that the Indus Valley copper most likely came from the Indian ores in the Rajputana district and Baluchistan, though Afghanistan and Persian sources are not absolutely ruled out

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It is believed that the furnaces employed for the smelting of copper ores were simply a concave depression in the ground Kilns have not yet been identified with certainty There is evidence that charcoal was used as a fuel The pits were lined with clay. A layer of charcoal was probably first placed on the floor of the pit and ignited Over this the ore and charcoal in alternate layers might have been arranged and the firing maintained by the aid of a blast

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The use of gold was confined to jewellery in the Indus Valley, while silver was used for jewellery and also for ornamental vessels Gold was obtained from South Indian gold fields in Mysore and Madras Silver might have been obtained with gold from the same source or from argentiferous lead of Burma. Articles made of gold-silver alloy, electrum, have also been found at Mohenjo-daro. A sample of silver found at Mohenjo-daro has been found on analysis by Hamid (archæological chemist) to contain

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| Silver | . | 94·52 per cent. |
| Lead | . | 0·42 „ |
| Copper | . | 3.68 „ |
| Insolubles . (silver chloride etc.) | .. | 0.88 „ |

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This seems to indicate that the silver was obtained by smelting argentiferous lead ore associated with cuprite of which the cerussite, found at Baluchistan, might be a probable source. The process of extracting silver from lead was undoubtedly known to the people of the Indus Valley. Silver might have been obtained also from Afghanistan and Persia. From Persia, too, gold may have been obtained and more certainly tin and lead.

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Minerals

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A large number of minerals, ores and rocks were known to, and in use among, the Indus Valley people. These include lapislazuli, turquoise, rock crystal, limestone, soapstone, alabaster, hæmatite, amethyst, slate, agate, jasper, chalcedony onyx, bitumen, steatite, sodalite, jade, lollingite, arsenical pyrites, etc. Most of these were found in the form of beads, pendants, etc. for ornamental purposes, and some like steatite were often coated with a glaze. Lollingite and leucopyrites were also utilized for the preparation of arsenious oxide and arsenic. Cerrusite and cinnabar have also been found at Mohenjodaro. They were probably used for cosmetics and medicinal purposes. White lead was possibly utilized for plasters, eyesalves and hair-washes. Galena was employed for the preparation of eye-salves and paints.

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Bitumen, alabaster and steatite were probably obtained from Baluchistan. Turquoise and lapislazuli are certainly of Persian or Afghan origin. Hæmatite was imported from the islands of the Persian gulf. Agates, carnelians, onyx and chalcedony, as also rock crystal, were obtained from Kathiawar region. Rajputana is most likely to have provided steatite, slate, jasper, chalcedony, etc.

Dyeing

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Finally, it might be mentioned that evidence has been obtained that the Indus Valley people were acquainted with the art of dyeing cotton with the red colouring matter of the madder root.

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CHAPTER III

History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c12: Chapter Ii. Indus Valley Civilization

Contents

Chapter Ii. Indus Valley Civilization

Table Iii

Dyeing

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