494 
Dr. Brinkley’s remarks on 
Explanations of, and Remarks relative to, the preceding Tables . 
Table I. contains the difference of polar distances of y Dra- 
conis and a Lyras, reduced to January 1, 1815, from obser- 
vations with the Greenwich mural circle, of both stars on each 
of 337 days from 1812 to 1816 inclusive. In the years 1812 
and 1813 six microscopes were used, afterwards only two. 
The greatest arc is that of September 16, 1816, and the 
least, that of July 21, 1812. 
The former - — 12 0 53' 52", 67. 
The latter - - - ™ 12 53 45 ,95- 
The mean of 337 Observations — 12 53 49 ,30. 
Table II. contains the differences from the Greenwich 
observations of the polar distances of a Lyras and Polaris, 
reduced to January 1, 1815, for three winters, together with 
the difference by the standard catalogue. 
These arcs are discordant among themselves, and the last 
of them singularly differs from the standard catalogue. 
The latter part of this Table exhibits the arcs when both 
stars were observed on the same day, in the winter 1815-1816. 
It is conceived there is no reason to expect that the arc, ex- 
ceeding 150°, between the direct and reflected images of « 
Lyras, can be more exactly measured than the arc, about 50°, 
between Polaris and a Lyras. 
Table III. The great irregularities that take place in the 
readings of the microscopes of the Greenwich circle, when 
there appears to be no cause for such, are very remarkable. 
Part ( 1 ) of Table III. exhibits the difference between the 
microscope A and each of the other microscopes, on every 
other day, when a Lyras was observed from July, 1813, to 
February, 1814. 
