TRIGONOMETRY of the BRAHMINS. 103 



rudiments are not older in Greece than 130 years before oxir sera. 

 The bare exiftence of trigonometrical tables, though they belong 

 undoubtedly to a very elementary branch of fcience, yet argues a. 

 ftate of greater advancement in the mathematics than may at firfl- 

 be imagined, and neceffarily fuppofes the application of geome- 

 trical reafoning to fome of the more difEcult problems of aftro- 

 nomy and geography. 



As long as the furveying of land, and the ordinary menfura- 

 tion of furfaces and folids, are the only practical arts to which 

 the geometer applies his fpeculations, he will naturally content 

 himfelf with conftrudling his figures and plans by means of a 

 fcale, and an inftrument for meafuring angles, as by doing fo 

 he may attain to all the accuracy he can defire. But when, iix 

 the figures that are to be thus delineated, the fides happen to be 

 extremely unequal, and fome of the angles very acute, or very 

 obtufe, graphical operations become inaccurate, and a very fmall 

 error in the meafuring of one thing produces an enormous error 

 in the eflimation of fome other. Lines, therefore, that extend over 

 a great tradl of the earth's furface, and much niore thofe that 

 extend to the heavens, cannot be compared with the fmaller lines^ 

 which we have an opportunity of meafuring, by the bare con- 



ftrudlion: 



(Tranf. R. S. Edin. vol. II. p. 164.) Mr Davis concludes from this, (Afiatic Re- 

 fearches, vol. II. p. 238), that if the obliquity dimini(h, at the rate of 50" in a hun- 

 dred years, the Surya Siddhanta is at prcfent about 3840 years old, which goes back, 

 nearly 2000 years before the Chriftian sera. But the diminution of the obliquity of 

 the ecliptic, is fuppofed confiderably too rapid in this calculation. According to- 

 Mayer it is 46'' in a centnry ; and according to De la Grange, (Mem. Berlin 

 1782), at a medium no more than 30". Tliis laft is moft to be depended on, as it 

 proceeds on an accurate inquiry into the law of the fecular variation of the obliquity, 

 that variation being by no means uniform. Let us however take the mean, viz. 38", 

 and the obliquity at the beginning of the prefent century having been 23°. 28'. 41'V 

 we fliall have 5000 years for the age of the Surya Siddhanta, reckoned from thaf 

 date, or about 3300 years before Christ, which is near the sera of the Caly Yaw,. 



