[ 307 H 
XXII. Results of the application of Captain Kater’s floating 
collimator to the astronomical circle at the observatory of Trinity 
College , Dublin, and remarks relative to those results . By the 
Rev. J. Brinkley, D.D. F. R. S P. R. I. A. Communicated 
by the Board of Longitude February 2, 1826. 
Read April 27, 1826. 
HP 
1 he results of the observations which I am about to state 
will, I think, be considered as affording a strong testimony of 
the importance of the floating collimator. As applied to my 
circle, it furnishes the means of ascertaining the index cor- 
rection with as great precision as by reversion, and in several 
points of view is undoubtedly superior to that method. 
The reversing principle of the Dublin circle serves very 
conveniently for a measure of the accuracy of the floating 
collimator, and appears to show satisfactorily, that in the 
application of this instrument to any circle, no error belong- 
ing to the instrument will be introduced into the results ; or 
in other words, that the results obtained by the assistance of 
the collimator, will not be sensibly affected by errors intro- 
duced by the collimator itself. 
In the series of observations which I send, will be found — 
I. The mean zenith distances of a number of stars, which 
were deduced solely by the application of the index correc- 
tion, as determined by the collimator. In this way the circle 
was used as a mural circle ; and as the observations were 
made both with the face of the circle east, and with the face 
