The city of Jaipur is the capital of Rajasthan, one of the North-Western States of the Indian Union. A large part of Rajasthan is covered by the Thar Desert and is the home of the Rajputs, a hardy and colourful people who have pro­duced many great warriors and kings. The Rajputs can also be proud of producing some great builders and building craftsmen whose skills have been utilised in buildings all over Northern India.

Jaipur has the distinction of being one of the planned his­torical cities of lndia. It was founded in 1727 by Mahara­jah Sawai Jai Singh II (1687-1743) to replace Amber as the capital of the then Rajput state of Jaipur. The original sett­lement at Amber was a fortress in the hills of the Aravali range. The new city was laid out at the base of this hill, in a triangular embayment of the plain, believed to be pan of the old lake-bed of a now shrunken lake. The planned city covers an area of about 8 km2 while today the urban area of Jaipur has expanded to over 65 km2. The core of the city was surrounded by a wall about six metres thick, having seven fortified gateways (pols), and an eighth was later added on the south side. Bastions and towers at regu­lar intervals completed the fortification which is still a stri­king feature of the city and helps to maintain its original identity.

The careful and systematic manner in which the city of Jaipur was planned and laid out is only one indication of the intelligence of Maharajah Sawai Jai Singh II. He distinguis­hed himself as a soldier, a builder, and a man of science. He was well versed in Sanskrit and Persian and was deeply interested in mathematics and astronomy. After devoting the early years of his reign to military campaigns, he soon settled down to his favourite pursuits of astronomy and his­tory. He sent an ambassador to Central Asia to bring infor­mation about the researches of Mirza Ulug Beg, the royal astronomer of Samarkand, who had constructed an obser­vatory at Samarkand around 1425. He also studied the ear­lier observatory built by the Persian astronomer, Nasir-ud­ din Al Tusi, as well as the instruments used by the Turkish astronomers and the tables of De la Hire sent to him by the king of Portugal. At the request of the Mughal Empe­ror, Muhammad Shah, he drew up a set of astronomical tables which he named Zij-i-Muharnmad Shahi. In the pre­face to this document, he explains how he came to build his unique astronomical observatories (later called Jantar Mantars) at the several locations of Delhi, Jaipur, Ujjain, Mathura and Benares.

In this extract, Jai Singh speaks of himself in the third per­son: “This admiring spectator of the theatre of infinite wisdom... was from the first dawning of reason in his mind and during his progress towards maturity, entirely devo­ted to the study of mathematical science... and by the aid of the Supreme Artificer he obtained a thorough know­ ledge of its principles and rules. He found that the calcu­lation of the places of the stars, as obtained from the tables in common use (Sanskrit, Arabic and European), in many cases give them widely different positions from those deter­ mined by observation, especially in the appearance of the new moons. Seeing that very important affairs, both regar­ding religion and the administration of the Empire, depend upon these... he represented the matter to the Emperor Muhammed Shah, who was pleased to reply: ‘Since you, who are learned in the mysteries of science, have a perfect knowledge of this matter, having assembled the astrono­mers and geometricians of the faith of Islam and the Brah­mans and Pandits and the astronomers of Europe, and having prepared all the apparatus of an observatory - do you so labour for the ascertaining of the point in question, that the disagreement between the calculated times of those phenomena and the times which they are observed to hap­ pen, may be rectified’.

“So he constructed at Delhi several instruments for astro­nomical observation... But finding that brass instruments did not come up to ideas which he had formed of accu­racy, because of the smallness of their size, the want of divi­sion into minutes, the shaking and wearing of their axes, the shifting of the planes of the instruments etc., he cons­tructed in Delhi instruments of his own invention, of stone and lime of perfect stability... such as Jai Prakash, Ram Yan­tra and Samrat Yantra... And, in order to verify the truth of these observations, he constructed instruments of the same kind in Sawai Jaipur, Mathura, Benares and Ujjain... so that every person who is devoted to these studies, when­ ever he wished to ascertain the place of a star, might observe the phenomena.”

Thus a unique architectural concept was implemented by Jai Singh in the construction of these observatories, where he laid out what were not just instruments but also, on account of their size, buildings in their own right with inte­rior chambers, steps, doors and occasionally even windows. The Jaipur Jantar Mantar is the largest and most splendid of these observatories. It is laid out in a court of the Maha­rajah’s palace and contains a large number of instruments for making different kinds of observation of the movement of heavenly bodies. Three of these instruments (yantras) are claimed to be originally devised by Jai Singh himself. These are the Samrat Yantra, the Jai Prakash Yantra and the Ram Yantra.

The largest and most striking of the instruments is the Sam­rat Yantra which is 29m. high. 47m. long and just as wide. It consists of a huge masonry gnomon or right-angled trian­gle standing vertical with its longer side on the ground and the hypotenuse pointing towards the pole. On either side of the gnomon is a masonry quadrant, each of about 15m. radius, with its centre lying on the edge of the gnomon. The edges of the gnomon and the quadrants are lined with white marble on which are incised graduations. The gno­mon also supports a straight flight of steps by which obser­vers can ascend to any pan of the instrument to take the readings.

The Jai Prakash Yantra consists of two hemispherical cavi­ties of equal diameter, suspended within a masonry struc­ture that is partially buried in the ground. The hemisphe­res represent half of the celestial sphere and their surfaces, lined with white marble, are marked with altitude and azi­muth circles, meridians, declination parallels, etc. The sur­faces of the hemispheres are cut by regular channels which form passages for the observer to walk within the instru­ment to take readings. The uncut portion of one hemis­phere corresponds to the cut portion in the other hemisphere, so that by moving from one to the other a complete map of the sky can be read on the two surfaces.

A similar idea is used in the Ram Yantra to facilitate the taking of readings. This yantra is also in two parts, each being a cylindrical construction of the same diameter, open at the top and having a pillar at its centre. The floor and the inside of the circular wall of each are graduated for alti­tude and azimuth observations. To allow for the movement of the observer within the instrument, the floors and the walls have twelve equal cuts - radially in the floor and ver­tically in the wall - corresponding to each other so that, by moving from one cylinder to the other, the graduations can be read for the whole surface horizontal as well as vertical.

A special feature of the Jaipur Jamar Mantar is the collec­tion of twelve instruments which form the Rashivalayas Yantra. Each instrument of this yantra corresponds to a sign of the zodiac (rashi). The instruments have been so cons­tructed and laid out that a particular rashi is available for use at the instant that the zodiacal sign reaches the meri­dian. Each instrument is composed of a gnomon and qua­drants as in the case of the Samrat Yamra. However, the rashis are only about five metres high, with a radius of the quadrants less than two metres. The instruments are used

in the same way as the Samrat Yantra. Just as the quadrants of the Samrat represent the equator, so the quadrants of the Rashivalaya represent the ecliptic, and as the gnomon of the Samrat points towards the pole, so the gnomon of the Rashivalaya points at the moment of the observation towards the pole of the ecliptic. The twelve instruments enable observations to be made approximately every two hours.

The entire collection of these masonry instruments at the Jamar Mantar presents a most remarkable sight. For some people, they even possess a magical quality. It is clear that Maharaja Jai Singh was not only a geometer of exceptio­nal skill, he also showed great sensitivity to the principles of spatial planning. The instruments are laid out with an apparent informality which only serves to enhance the monumental quality of the individual structures with their geometrically determined lines and bold plastic massing. The wall surfaces are free from the intricate ornamentation characteristic of the late Mughal style prevalent in this period. This helps to set off the powerful rhythm of the voids and the drama of the flights of steps, all creating fascinating patterns of light and shadow. Although it is clear that the structures are functional in nature and serve a tech­nological purpose, the overall composition of forms is espe­cially memorable since it becomes a configuration of abs­ tract spaces and interpenetrating solids so close to the Pla­tonic ideal that it could easily be mistaken for the work of some 20th century cubist master.