334 Dr. Brinkley’s observations jor investigating 
figure or otherwise, occasion the discordances of the zenith 
distances. If this were so, it must exist for all stars ; and 
Table 2 shows satisfactorily it does not exist; for those ob- 
served when the difference of temperatures is greater than 
when a. Lyras, a. Aquilas, &c. were observed. 
The same is deduced from the observations of the Pole 
Star. If the instrument give different results for the same 
angle, it must appear in the co-latitude determined by the 
Pole Star at different seasons. The co-latitude found by co- 
temporaneous observations above and below the pole, is not 
affected by any uncertainty in the quantity of aberration, or 
in the parallax of the Pole Star ; it therefore affords a good 
criterion of the permanency of the scale of measurement of 
the instrument, if I may so express myself. The quantities 
are as follow : 
No. of 
Observations. 
Z. D. Pole Star. 
Co-latitude. 
Autumn | 
72 
76 S.P. 
0 1 11 
3457 21,24 
38 l6' 11,84 
0 / // 
| 36 36 46,53 
Winter j 
72 
64 S.P. 
345721,51 
38 1611,89 
| 36 3 6 4> 6 >7° 
Spring | 
64 
71 S.P. 
3457 21,26 
38 16 11,71 
} 36 36 46,49 
Summer j 
72 
60 S.P. 
345721,87 
38 16 12,13 
} 3 6 3 6 47>°° 
2. There may be an effect produced from the relative 
