Preceffion of the Equinoxes. 515 
tor in the circle of the Sun’s declination while the center 
of the earth is carried through the lpace z of its orbit is 
equal to - 3 P mnx and may he fuppofed to be equal to 
2 ST 1 X I — Up 
3 l!H± the alteration produced by the correction in art. 
2 ST' 7 
4. on account of the fpheroidical figure of the earth 
being too inconfiderable to affeCt the conclufion. 
6 6. IV e are to obferve, that the fpace defcribed 
by that point of the equator, which is the interfeclion of 
the circle of the Sun’s declination, is generated by the 
perpetual attraction of the Sun. This attraction may be 
reckoned conftant during the very fmall time of the 
earth’s defcribing z in its annual motion; and, therefore, 
the faid point of the equator, at the end of that time, will 
have acquired a velocity which would carry it through 
iiEIPL i n the fame time. 
ST 2 
§ 7. Let t reprefent the time of the earth’s revolution 
in its orbit, t the time of its rotation round its axis, 
and fuppofe w to be a fmall arc fimilar to z in a circle 
whofe radius is unity. In figure 5. let aqJjc the equa- 
tor, and take kb equal to and bt perpendicular to kb 
equal to o,pmnw z , and kb, bt, will reprefent the direc- 
tions and quantities of the two different motions of the 
point a, and confequently a t will be the direction of the 
3 new 
