( II ) 
n. A Difcourfe concerning a Method of Difco^er- 
ing the true Moment of the Suns Ingrefs into 
the Tropical Signs. By E. Halley. 
I^T may perhaps pafs for a Paradox, if not feem ex- 
travagant, if I fliould aflert that it is an eafier mat- 
ter to be alTured of. tlie moments of the Tropicks, or 
of the times of ihtSm's entrance into Cancer andC<a- 
pricorn, than it is toobferve the true times of the Equi- 
ooftial^ or Ingrefs into Aries and Liira, 1 know the 
Opinion both of Ancient and Modern Aftronomers to 
the contrary ; Ptolemy fays exprefly, Ta^ riv f^-niv 
ThfYKFii^'hjfjiisLyt^'t^c, S.vcuj ; And Rkciolus begins his Chap- 
ter of the Soifdtial Oblervations with thefe words. Me- 
rit; oSmlYwxs, in notis ad olfervationes Hafliacas, />/'£?;/«m^. 
'vity Herculei effe lahoris vitare in Solftitiis ohfirvandis 
errorem quadrantis diei^ and this becaufe of the exceed- 
ing flpwnefs of the change of the Sun's Declination on 
the day of the Tropick, being not a quarter of a Minute 
in X4 Hours. This indeed would make it very difB-. 
cult,' nor would any Inftruments fufiice to do it, were 
:the mo'^^ent of the Tropick to be determined from one 
fingle Obfervation. But by three fiibftquent Obferva- 
tions m: :^*e near the Tropick,ac proper intervals of time, 
?I hereby defign to (liew a Method to find the moment 
of the Tropicks capable of all the exaftnefs the mofl 
Accurate can defire,- and that without any confideration 
of the Parallax of the Sun, of the Refradions of the 
Air, of the greateft Obliquity of the Ecliptick, or La- 
titude of the Place : All which are required to afcertain 
'the times of the Equinoftials from Obfervation, and 
•which being faultily aflumed, have occafioned an Error 
•of near three Hours in the times of the Equinodials<le- 
duced from the Tables of the Noble Tycho Brake and 
Kepler^ 
