log 
Sir George Shuckburgh's Account 
may be done, if necessary. Lastly, from taking a mean of all 
the numbers in the 4th column, it seems the probable error, 
in reading off the divisions, is only o ",53 in the equatorial 
circle, and o",^y in the declination circle. This source of er- 
ror may therefore be put at o"\ ; so that if one quadrant 
only of the circle should be made use of, viz. only one mi- 
crometer, and that only once read off, it is probable that no 
error of more than will be committed. I mention this, 
because it will sometimes happen that only one such observa- 
tion can be made ; but where sufficient leisure will allow the 
reading off both the microscopes, this small error of will 
probably be halved ; and if the declination circle be turned 
half round, and the observation repeated, in the same man- 
ner, upon the two remaining quadrants of the circle, as is 
done (we shall presently see) when the line of collimation is 
examined, this error will probably be quartered, or reduced to 
less than o"±. 
After the very rigorous examination the divisions of these 
two circles have now undergone, and from the general know- 
ledge that I have had opportunities to obtain of the state of 
practical astronomy in different countries ; and when I con- 
sider that the celebrated artist, the late Mr. John Bird, 
seems to have admitted a probable discrepancy in the divi- 
sions of his 8 feet quadrants, amounting to * 3", I think I am 
entitled to believe that the accuracy of these divisions under 
consideration is hardly to be equalled, and still less to be ex- 
celled, by that of any astronomical instrument in Europe ; 
and, from the unexampled diligence and care, with which the 
skilful artist Mr. Matthew Berge, workman to Mr. Rams- 
* See Mr. Bird’s Method of constructing Mural Quadrants. London, 1768. 
