C »49 ) 
and by the Complement of the Pole’s Elevation, the 
Author lliews, that the Variation of the Angle at the 
Pole, and confequently the Error in Time, will be as 
the Error in the Altitude diredly, as the Sine Conv 
plement of the Pole’s Elevation inverfely, and as the 
Sine of the Star’s Azimuth from the Meridian in- 
yerfely. Confequently, if the Error in the Altitude 
be given, under a given Elevation of the Pole, the Er- 
ror in Time will be reciprocally as the Sine of the- 
Azimuth contained by the Meridian and the Vertical 
which the Star is in. This Error therefore will be the 
fame, whatever be the Altitude of the Star in the fame 
Vertical; and will be lead when the Vertical is at 
right Angles to the Meridian. But will be abfblutely 
the lead in the fame Circumdance, if the Obferver be 
under the ^Equator. In which Cafe, if the Error in 
the Altitude be one Minute, the Error in the Time will 
be four Seconds, If the Oblcrver recedes from the 
.Equator towards either Pole, the Error will be in- 
creafed in the Proportion of the Radius to the Sine 
Complement of the Latitude : So that in the Latitude 
of 45“ Degrees it will be 5* * Seconds, and in the Latitudes 
of 50 and d will be6i and Seconds relpedfively. 
If the Star be in any other vertical Oblique to the Me- 
ridian, the Error will dill be increafed in the Proporti- 
on of the Radius to the Sine of that oblique Angle. 
Ladly, if the Error in the Altitude be either bigger or 
iefs than one Minute, the Error in Time will be big- 
ger or lels in the lame Proportion. Much after the 
fame manner may the Limits of Errors be computed in 
otha Cafes,which arife from the Inaccuracy of Obferva- 
tions, and from hence the mod convenient Opportu- 
nities for oblerving are alfo determined. 
The Second Treatile is concerning \X\^T^ijferential 
Method, The Author having wrote it, before he had 
B b feen 
