176 REMARKS on the 



52. Since an inequality was firft obferved in the motions of 

 the fun or moon, the difcovery of the law which it follows, 

 and the method of determining the quantity of it, in the 

 different points of their orbits, has been a problem of the 

 greateft importance ', and it is curious to inquire, in what man- 

 ner the aftronomers of India have proceeded to refolve it. For 

 this purpofe, we muft examine the tables of the chaiaa^ or 

 equations of the centre for the fun and moon, and of the manda t 

 or equations of the centre for the planets. With refpect to the 

 firft, as contained in the tables of Siam, M. Cassini obferved, 

 that the equations followed the ratio of the fines of the mean 

 diftances from the apogee ; but as they were calculated only for 

 a few points of the orbit, it could not be known with what 

 degree of exaclnefs this law was obferved. Here, however, the 

 tables of Chrifnabouram remove the uncertainty, as they give 

 the equation of the centre for every degree of the mean mo- 

 tion, and make it nearly as the fine of the diftance from the 

 apogee. 



They do fo ; however, only nearly ; and it will be found on 

 trial, that there is, in the numbers of the table, a fmall, but re- 

 gular variation from this law, which is greateft when the ar- 

 gument is 30% though even there it does not amount to a mi- 

 nute. The fun's equation, for inftance, which, when greateft, 

 or when the argument is 90 , is, by thefe tables, 2°, 10', 32", 

 fhould be, when the argument is 30 , juft the half of this, or 

 i°, 5', t6", did the numbers in the table follow exaclly the 



ratio 



la lune ojfenfee du dragon. Whether it be that we have borrowed thefe abfurdities from 

 India, along with aftrology, or if the popular theory of eclipfes has, at firft, been every 

 where the fame, the moon's node is alfo known with us by the name of the cauda dra- 

 conis. In general, however, the fignification of the terms in thefe rules, fo far as we 

 know it, is more rational. In one of them we may remark considerable refinement; 

 ayanangfam, which is the name for the reduction made on the fun's longitude, on account 

 of the preceflion of the equinoxes, is compounded from ayanarn, z courfe, and angfam, 

 an atom. Mem. Acad. II. P. 251. The equinox is almoft the only point not diftin- 

 guifhed by a vifible objecl:, of which the courfe or motion is computed in this aftronomy. 



