a floating collimator. 
Long float browned. 
167 
24th Set. 
Divisions 
of 
Microm. 
Difference. 
Error in Sec’, 
affecting the 
Horiz. point. 
Jan. 3 
Out and replaced, S first - - 
Ditto - - ditto - - 
Ditto - - ditto — - 
Ditto - ditto - - 
51.1 
49’4 
48.7 
50.2 
— *.7 
— o >7 
+ 
it 
— 0,51 
— 0,21 
+ 0,45 
25 th Set. 
Jan. 3 
Out and replaced, S first - - 
Ditto - ditto - - 
Ditto - ditto - - 
Ditto - ditto - - 
Ditto - ditto — — 
Ditto - ditto - - 
57.5 
56,7 
60,3 
57^4 
59^0 
58,1 
— 0,8 
+ 3>6 
— 2,9 
4 " 
— 0,9 
// 
— 0,24 
+ 
— 0,87 
+ 0,48 
— 0,27 
26th Set. 
Out and replaced, S first - - 
Ditto - - ditto - - 
Ditto - - ditto - - 
Ditto - - ditto — - 
Ditto V- - ditto - - 
Ditto - - ditto - - 
1 
63>3 
63,6 
61.1 
59>6 
60,9 
6 1.2 
+ 0,3 
— 2,5 
— 
-f *>3 
— 0^3 
+ 0,09 
— 0.75 
— 0,4.5 
+ 0^39 
— 0,09 
Of the one hundred and fifty one results in the column 
indicating the errors affecting the determination of the hori- 
zontal point, only twenty-eight are found exceeding one 
second ; viz. one of 2'',58, another of 2", 01, ten between two 
seconds and one second and a half, and sixteen between a 
second and a half and one second ; the remaining one hundred 
and twenty-three errors being all less than one second. 
But as it is not to be supposed that an observer would be 
satisfied with a single determination, when he has the power 
in a very few minutes of attaining far greater accuracy, I shall 
