H9 
of the Equatorial Instrument. 
sun not suffered to shine on the instrument, only 
during the moment of observation, I think no error 
in the polar distance need be apprehended exceeding 7, 
And in the meridian passage, none exceeding - 3,5 
So that it appears, that the right ascension will be observed 
with twice the precision of the polar distance. 
And here we must not omit to take notice, that of all the 
above mentioned causes of error, one only, viz. the error of 
the divisions in taking the polar distances, appears to be fixed, 
so that, by repeating the observation, the truth may be ap- 
proached to any given degree of accuracy. I have thought 
proper to make these remarks on the errors of the instru- 
ment, that if health and leisure should enable me hereafter to 
offer to the Royal Society the result of any astronomical ob- 
servations with it, it may be known to what claim to precision 
they are entitled. 
In describing the instrument, the following references in 
Tab. IX. were omitted in the text. 
ff> gg> bb 9 ii, are the eight conical radii to the declination 
circle, described page 78. 
11, 12, are two supporters to the clamp and endless screw, 
page 80. 
36, is a pair of steps, for the convenience of the observer. 
