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claims to remembrance are that " he was the founder of a new capital named after 

 him, Jainagar or Jaipur, which in his time became a centre of learning ; he 

 erected caravanserais in many of the provinces ; and he built astronomical 

 observatories at five of the principal cities of Hindustan. He conceived and 

 carried out a scheme of scientific research that is still a notable example." Jai 

 Singh early showed a predilection for astronomical work, and studied earnestly 

 the work of his predecessors and contemporaries, Hindu, Muslim, and European. 

 He prepared a set of astronomical tables based on those of Ulugh Beg, of which 

 Mr. Kaye gives an interesting description as well as copious extracts to show the 

 manner in which the tables were drawn up. The preface to these tables, which 

 Mr. Kaye gives in full, is of great interest, because the reasons which led Jai 

 Singh to construct his peculiar masonry instruments are clearly stated. 



Jai Singh concluded that the errors in observation which were the cause of the 

 discrepancies between different catalogues were due partly to the smallness of 

 the metal instruments, such as the astrolabe, which were then in vogue and which 

 resulted in division errors and errors of reading, and partly to the shaking and 

 wearing of pivots, displacement of the centres of the circles, etc. It is now 

 recognised that instrumental errors are inevitable, and the modern astronomer 

 does not attempt to eliminate them absolutely, but reduces them to a small 

 magnitude, and then determines them separately with as much accuracy as 

 possible. Jai Singh came to the erroneous conclusion, however, that these 

 defects could be overcome by constructing "instruments of his own invention, 

 such as Jai Prakas and Ram Yantra and Samrat Yantra, the semi-diameter 

 of which is of eighteen cubits, and one minute on it is a barley-corn and a half — 

 of stone and lime of perfect stability, with attention to the rules of geometry 

 and adjustment to the meridian and to the latitude of the place, and with care 

 in the measuring and fixing of them, so that the inaccuracies from the shaking 

 of the circles and the wearing of the axes and displacement of their centres, 

 and the inequality of the minutes might be corrected." 



The fundamental assumptions are inherently incorrect : they presuppose in 

 theory that the only bar to accuracy of observation was the limit imposed by 

 circumstances on the size of the instrument, and require in practice an absolutely 

 accurate knowledge of the latitude and meridian, and no errors in construction. 

 The errors in the observations made with them were not less than those in older 

 observations. The basic ideas of the instruments were not peculiar to Jai Singh, 

 although much ingenuity was shown by him in working them out. Mr. Kaye 

 traces in an interesting manner their probable evolution. For the purpose of 

 expounding the elementary fundamental ideas of astronomy they would serve 

 admirably. Space does not permit of a description of the instruments ; for these 

 the reader should consult Mr. Kaye's book. 



A detailed account is given of Hindu metal instruments, many of which are of 

 exquisite workmanship. It was upon these that Jai Singh attempted to improve. 

 A general account of the various instruments constructed by him is then given, 

 and this is followed by detailed descriptions of the several observatories, with 

 remarks as to the repairs, etc., necessary for their proper reconstruction and 

 preservation. A general historical perspective follows, with an attempt to 

 evaluate Jai Singh's work. Numerous useful tables are given at the end of the 

 volume. 



Mr. Kaye has written a book of great interest from the archaeological, historical, 

 and astronomical view-points. It is much to be hoped that the recommendations 

 which he puts forward for putting the observatories into a proper condition, and 



