[ 33 8 ] 
(t little equations, the fum of which may produce 
“ above three feconds of time; 2dly, becaule it has 
“ been the practice to convert the equation of the 
“ fun’s centre, and the difference between his right 
<c afcenfion and longitude into time of the Primum 
« Mobile, inftead of converting them into mean 
“ folar time, which, fays he, may produce an error 
“ of two feconds and a half ; 3 dly, becaufe the 
<c equation of the fun’s centre was not known ex- 
“ adly before, every minute of which anfwers to 
“ four feconds in the equation of time. 
I readily agree with M. Delalande, that the equa- 
tion of time could not be had foexadly formerly, as 
it may now, when we have a much more exad 
theory of the lun, and are lately made acquainted 
with new equations of his motion. I cannot, how- 
ever, affent to his pofition, that the equation of the 
equinodial points is to be taken into this account, 
together with the other equations, fince this is not an 
inequality in the fun’s motion, but arifes from a mo- 
tion of the equator itfelf ; yet of fuch a kind as can- 
not accelerate or retard the coming of the fun, or 
any ftar lying within the tropics, to the meridian, by 
above a quarter of a fecond of time. . This will, 
perhaps, appear in a good meafure plain, if it be 
coniidered, that the diurnal motion of the earth 
round its axis is neither accelerated nor retarded by 
the adion of the fun and moon in producing the pre- 
ceffion of the equinoxes, and variations of the incli- 
nation of the earth’s axis to the ecliptic. The effed 
of thefe adions is, that the terreftrial pole, each day, 
defcribes a fmall arc of a circle about the centre of 
the earth, in the plane of a celeftial meridian palling 
through 
2 
