Ona New Method of recording differences of Declination. §& 
deviation from the uniformity of the placing of the dots. I sus+ 
pected this to be owing to the action of the wires attached to the 
arm and conducting the current from the battery through the 
electro-magnet. Ample length was given to the wire, but there 
yet remained in it a sufficient stiffness to affect the place of the 
arm in its extreme positions, by a minute amount. ‘This was 
fully demonstrated by experiment on the following night. A star 
was brought to bisection on a wire, and while thus located, the 
conducting wires were geutly touched by the hand of the. ob- 
rand the instrument was seen to yield to every touch. A 
source of error was thus detected of a minute character indeed, 
but of vast importance where tenths of seconds of are were the 
quantities under examination. The admirable agreement now 
found to exist uniformly between the work of different nights 
encouraged me to go back and remeasure with greater care the old 
work still remaining engraved on the plate. By using a mean of 
two or three measures the observations were brought to the most 
surprising coincidence. I did not attempt a remeasure of all the 
observations, but contented myself with a rigid examination of a 
single pair of N. A. stars, among whose observed differences of 
declination average discrepancies existed. I copy the final re- 
sults, remarking simply that the observations were made between 
the 26th May and the 30th June inclusive 
The following are the decimals of a revolution of the microme- 
ter screw in the ten observations. 
Second of arc. 
a agen to é Bootis -6836 Diff. from mean (0017. = *; - 
‘6609+ “ 9210 
oP) BOD 4.0) ct 7 RES sas 
Fes | , “s *6883° cc ee 0064 0 -256 
6c 6 6906 7 “sc ‘0085 0 340 
3 = 6757 “ in; See 0 -208 
“ “« 6699 «  -0120 0 -480 
“ 6c ec rt -0067 0 -268 
(73 ce *6905 “c 6c “0086 0 +344 
“ Se, PETS oe “  -0054 0 220 
Mean -6819 0 -340 
Prob. error, 0/250 
« Cor. to ¢ Bootis, Greenwich Obs., 1840, 
‘6 “ £6 
0-05 
' 1 61 
“ mc ; + b 64... 
$s ng “ 1 -02 
$ ag ie ey 
“ ‘ “ > 67 > 
fs ee “ec “ 1 -39 
: “  “ “ 0-81 ~ 
ie 4 sa i 20 4 - 
oe ri “ 2 520 Peer 
re - Teas 
si a “401 Prob. error, 13. 
