• N DIVIDING INSTRUMENTS. l^ 



Example 3. 



Point 83°*6, or last point, of the third quadrant 

 Real errour of the poin t 84°'4 of t he third 



quadrant — . 21** 



Real errour of the point 2°'8 of the fourth 



quadrant — 2*9 



Half sum — U'9 



Apparent errour of the dot under trial — 4*0 



Real errour • . . . — 15*9 



Example 4. 



Point 88**6, or last, of the fourth quadrant. 

 Real errour of the point 84°*4 of the fourth 



quadrant — 21*6 



Real errour of the point 2'"'8 of the first quad- 

 rant — 10»2 



Half sum — 15-0 



Apparent errour of the dot under trial -{- 9*5 



Real errour — , 6*4 



It is convenient, in the formation of the table of real er- 

 rours, that they should be inserted in the order of the num- 

 bering of the degrees on their respective quadrants; al- 

 though their computation necessarily took place in the or- 

 der in which the examination was carried on, or according to 

 the arrangement in the table of apparent errours. The firgt 

 dot of the first quadrant having been assumed to be in its 

 true place, the first of the third quadrant will err by just 

 half the difference found by the examination ; therefore these 

 errours are alike in both tables. The real errour of the first 

 dot of the second quadrant comes out in the first example ; 

 that of the fourth was found in like manner, and completes 

 the first line. Tt is convenient to put the errour of the di- 

 vision 90° of each quadrant at the bottom of each column, 

 although it is the Siame as the point 0* on the following 

 quadrant. The line 45° is next filled up ; the second exam- 

 ple shows this; but there is no occasion to dwell longer up- 

 on this explanation ; for every one, who is at all fit for such 



Vol. XXV— .J an. 1810. C pursuits. 



