176 REMARKS on the 



^2. 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 mufl examine the tables of the cbaiaa, or 

 equations of the centre for the fun and moon, and of the manJa, 

 or equations of the centre for the planets. With refpecSt 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 

 diflances 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 exatftnefs 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 amotmt to a mi- 

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

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

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

 1°, 5', t6", did the numbers in the table follow exadly the 



ratio 



/fl /uite offenfee 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 fij,nification of the terms in thefe rules, fo far as we 

 know it, is more rational. In one of them we may remark confiderable refinement j 

 ayanangjatn, which is the name for the reduftion made on the fun's longitude, on account 

 of the precelTion of the equinoxes, is compounded from ayanam, a courfc, and angfam, 

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

 guiflied by a vifible objeft, of which tlie courfe or motion is computed in this aftronomy. 



