sol Mijcdlanea Curioft. 



j4 c Difeourfe concerning a Method 

 of c Difcovering the true Moment 

 of the Suns Ingrefs into the Tro* 

 f ical Sines. 



By E. Halley. 



TT may perhaps pafs for a Paradox, if not 

 feem extravagant, if I fliould affert that 

 it is an eafier matter to be aflur'd of the 

 Moments of the Tropicks, or of the Times 

 of the Surfs Entrance into Cancer and Capri- 

 com, than it is to obferve the true Times 

 of the Equino&ials or Ingrefs into Aries and 

 Libra. I know the Opinion both of Ancient 

 and Modern Aftronomers to the contrary ; 

 Ptolemy lays expreily, Tds rcov tzjitZv Twfam 

 £v<r£ici,KttT<ss Zvau'y And Ricciolm begins his 

 Chapter of the Solftitial Obfervations with 

 thefe words, Merit o Snellius, in notis ad ob- 

 fervationes Haifiacas, fronunciavit, Herculei ejfe 

 laboris vitare in SolftitiiS obfervandis errorem 

 quadrantis diei^ and this becaufe of the ex- 

 ceeding flownefs of the change of the Sun's 

 Declination on the day of the Tropick, be- 

 ing not a quarter of a Minute in twenty 

 four Hours. This indeed would make it ve- 

 ry difficult, nor would any Inftruments fuffice 

 to do it, were the Moment of the Tropick 

 to be determin'd from one Jingle Obferva- 

 tion. But by three fubfequent Obfervations 



made 



