“PHYSICAL ann LITERARY. 179 
- more ufeful, that the ufual methods of ta- 
_ king the latitude of places by the fun’s me- 
| ridian altitudes, fuppofes the tables of his de- 
clination to be perfectly juft; whereas there 
is ground to doubt of their precifenefs. 
MaTuHeMATICAL in{truments in general, 
and fuch particularly as ferve for aftronomi- 
cal purpofes, have been, of late, brought to 
an exac¢tnefs never known'in former times. 
Hence fome minute motions, or inequalities 
of motions, in the heavens, may be difcovered, 
that have hitherto efcaped the moft diligent 
obfervers. They had difcovered indeed fome 
motions that are very minute or flow, fuch 
asthe preceffion of the equinoxes; but this 
was owing to the continual increafe of the 
effects of thofe very minute motions, which, 
tho’ infen§ble in one revolution, become ve- 
ry manifeft in many revolutions. Motions 
of this kind are eafily found, and are accu- 
rately determined, by comparing diftant ob- 
| fervations. _ But there are other minute mo- 
tions which are hard to be difcovered: thefe 
which do not grow up to be fenfible in a 
art deftroying their effect in another part 
of arevolution. Of this kind is the mo- 
Lae 2 tion 
4 d - \ 
Tie nN > 
umber of revolutions; their effect in one’ 
