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a floating collimator. 
The end of the box next the object glass of the telescope 
was raised so that the mercury ran from beneath the float 
to the other end of the box ; it was then restored to its for- 
mer position ; this for the sake of brevity I shall designate 
by O raised. 
The eye end of the. box was elevated and restored to its 
place in like manner ; this I have called E raised. 
One side of the box elevated and replaced, ♦S' raised. 
The other side of the box treated in like manner, S s raised. 
The object end of the box raised, and the box carried in 
that position to the other side of the observatory, brought 
back and replaced, O raised and carried. 
The eye end raised, and tlie box carried and replaced, 
E raised and carried. 
S raised and carried, and S.s raised and carried, signify simi- 
lar operations, previously elevating one side or other of the 
box. 
Out and replaced O first, signifies that the float was lifted 
quite out of the mercury and the box replaced, the end 
of the float next the object glass being brought first into 
contact with the mercury. 
Out and replaced, E first, the same, with the eye end. of the 
float first brought in contact with the mercury. 
Out and replaced S first, the same with one side brought 
first into contact. 
Out and replaced' S s first , the same with the other side 
brought first into contact. 
As soon as the cross wires appeared to be perfectly at 
rest, the angle was carefully bisected by the micrometer 
