a floating collimator. 
165 
Short heavy Float. 
i8th Set. 
Divisions 
of 
Mierom. 
Difference 
Error in Sec®, 
affecting the 
Horiz. point. 
Dec. 30 
A.M. 
Out and replaced, S first 
Diito - ditto 
Ditto - ditto 
Ditto - ditto 
Ditto - ditto 
Ditto - ditto 
32.1 
34’9 
34>7 
33»2 
34.2 
31,8 
4- 
— 0,2 
— 1.5 
+ 1,0 
2,4 
-f 0,84 
— 0,06 
— 0,45 
+ 0,30 
— 0,72 
Experiments to show the effect of turning the box round. 
19 th Set. 
Previous to moving 
Turned round 
Back again - 
Turned round - - - 
Back again - - - 
Turned round 
31,0 
33,2 
33,9 
32.6 
30.7 
3‘,3 
+ 2,2 
+ 0,7 
— 1^3 
— 1,9 
+ 0,6 
4" 0,00 
4- 0,21 
— 0,39 
— 0,57 
4- 0,18 
Mercury carefully strained. 
20th Set, 
Out and replaced, S first 
Ditto — ~ ditto ~ - 
Ditto - — ditto - - 
Ditto - ditto 
Ditto - ditto - - 
Ditto ' - ditto - 
21,1 
27.0 
22.1 
25,7 
24»4 
33,6 
+ 5.9 
— 4>9 
4- 3,6 
— 1,3 
— 0,8 
4 - 1,77 
— »,47 
4- 1,08 
— 0,39 
— 0,24 
Great care taken that the side of the float should be in 
contact \vith the mercury its whole length, previously to 
putting down the surface. 
