May I, 19 19] 



NATURE 



167 



reproduced by Mr. Kaye in the valuable book 

 now under notice. In this introduction Hipparchus 

 is referred to as an ignorant clown, and 

 Ptolemy as a bat who can never arrive at the sun 

 of truth ; the demonstrations of Euclid are said 

 to be an imperfect sketch, and '* the European 

 tables " to be often in error. Jai Singh therefore 

 decided to erect new instruments of colossal size, 

 similar to those made by Ulugh Beg at Samar- 

 kand in the fifteenth century. Among the latter 

 we know from other sources that there was 

 a quadrant of i8o-ft. radius, while a 60-ft. 

 sextant is said to have been erected at Baghdad 

 in A.D. 992. Before the application of diag^onai 

 scales or verniers to graduated arcs there was 

 only one way of making single minutes and frac- 

 tions of them distinguishable — by enlarging the in- 



but gigantic sun-dials. Thus the Samr&i Yantra, 

 or "supreme instrument," consists of a gnomon 

 in the form of a rectangular triangle with the 

 hypotenuse parallel to the earth's axis, and an 

 equatorial arc on either side. The two largest 

 examples are at Delhi (height 68 ft., radius of 

 arcs 49^ ft.) and at Jaipur (90 ft. and 50 ft.) 

 (Fig. i). The Jai Prakas is a hemispherical bowl, 

 on the concave surface of which are marked the 

 equator, meridian, and other circles, on which the 

 shadows of wires might fall. The Ram Yantra 

 (Fig. 2) is a cylindrical wall with a vertical pillar 

 in the middle. Neither these nor any of the other 

 instruments show any originality of design. The 

 best known of these five collections of masonry 

 instruments is probably the Delhi Observatory, 

 called the Jantar Mantar, built about 1724, 



-The Ram Yantra, Delhi, North Building. From " The Astronomical Observatories of Jai Singh. 



struments as much as possible. Jai Singh first 

 constructed a number of astrolabes of iron or 

 brass, from 6 in. to 7 ft. in diameter, many 

 of which are still preserved at Jaipur. In four 

 plates Mr. Kaye gives sixteen photographic illus- 

 trations of these astrolabes, but most of them are 

 too indistinct to show details. 



Jai Singh's chief work, however, was the build- 

 ing of masonry instruments, ranging from a few 

 feet to 90 ft. in height, at Delhi, Jaipur, Ujjain, 

 Benares, and Mathura. They have often been 

 described in a more or less sketchy manner in 

 books on India ; but Mr. Kaye gives an ex- 

 haustive account of them, beautifully illustrated 

 by a number of plates. ^ They ane really nothing 



* There are a number of tiny models of them in the South Kensington 

 Museum. 



NO. 2583, VOL. 103] 



3^ miles south of the Ridge, so that it will be a 

 notable feature in the new capital. It contains six 

 instruments. The graduations on the gnomon of 

 the Samrdt Yantra are scratched into the lime- 

 plaster surface, but those of the quadrants are 

 well marked with a soft, black stone neatly inlaid 

 into the face of the arcs. This seems, however, 

 to be the result only of a restoration carried out 

 in 1910-12. At Jaipur the instruments are well 

 preserved, being within the precincts of the palace. 

 At Benares the instruments were erected in 1737 

 on the roof of a building; they are therefore of 

 moderate size. A much-needed restoration took 

 place in 191 2. At Ujjain the four instruments are 

 in a state of ruin, and those at Mathura have 

 quite disappeared. 



There is no record of any attempts having been 



