Mr. Pond on the Declinations 
4' 2 4 
from those observations, are of such infinite importance to the 
science, that every circumstance relating to it cannot fail of 
being interesting. Now when it is considered that this instru- 
ment has been in constant use for upwards of half a century, 
and that the center error, from constant friction, would during 
this time have a regular tendency to increase, it will not 
appear at all surprising, if the former accuracy of this instru- 
ment should be somewhat impaired. With a view, therefore, of 
ascertaining more correctly the present state of an instrument 
on which so much depends, I have exhibited in one view the 
polar distances as determined by circular instruments alone ; 
the respective co-latitudes being previously corrected by the 
method above mentioned, and I have compared the mean 
result with the Greenwich Catalogue, that the nature and 
amount of the deviations may be seen, and if it be judged 
necessary, corrected. I should add, that by some observa- 
tions of the sun at the winter solstice in 1800, the difference 
between the Greenwich quadrant and the circle was 10 or 12", 
the quadrant still giving the zenith distance too little. 
General Description of the Instrument. * 
The annexed Plate represents the circle in its vertical 
position. It was originally made to be used likewise as an 
equatorial instrument, a circumstance I need not have men- 
tioned, but as an apology for the slightness of its construction, 
which the artist who made it would not have recommended, 
had the instrument been intended for the vertical position 
only. 
The declination circle, 30 inches in diameter, is composed 
of two complete circles ; the conical radii of which are inserted 
