\ 
DECLINATION. 
zontal object at the extremity of the wire, move the obje& 
along the field of view-by means of the tangent- {crew to the 
azimuth circle, and obfer nve if it remain aia bifeGed 
till it arrives, at the other extremity ; if it does not, turn round 
the wires in their cell till this verification i is obtained 
Verification of the Ve erniers. 
Call the vernier which is connected with the clamp- -{crew 
No. 1, the others No. 2, No. 3, No. 4, in oo accord- 
ing to the divifions of the circle. Oo. I. 210, — 
off all the others, and fet down their pa ee 
fign + or —, as they exceed or fali fhort of their pei 
divifioas, add thele een and div fide the fum 
called the index error, and est be 
+ 
This quotient may b 
applied to the ai d angle with a cesta fign. e. 
No. 
. ‘ + oe 
3. : Ps +10 
AB 
4) +02 
" Index error to be 
+ 
fubtra&ed from the obferved angle : ha oe at the 
d 
end of an ene the verniers. ftand the 
No. ft. 183° 14’ 107 
2. ; 4 
ae , 14 
Ae * 20 
4) 5% 
183 14 12.77 
Dedu& Index error — 3 
True Angle : 183 14 9.47 
The obferver fhould take no ween that the circle, the level, 
and the front telefcope, all turn round one common axis, in- 
ome in obferving, it muft 
dependent of each other. N 
remembered, that the circle muft always be fixed to, and a 
one piece with one of the other two. In the front obfer- 
vation which begins the feries, it mu confidered 
forming one piece with front telefcope, and care muft 
e taken on no account to touch the fcrew that alters their 
relative pofition to each other nee contrary, in the re- 
verfe obfervation, the circle mutt be a 28 forming 
one piece with the level, and equal care taken not to fepa- 
_ The reat "danger : 
releafing the piece w 
But a little confideration and pimcuce will render this 
span eafy and familiar, 
A well regulated clock or watch is neceffary for thefe 
obfervations ; and they will be rendered much eafier, if an ag 
fiftant attends to the level, while the obferver bifecis the 
ments, that 
quite infenfible. The obferver will {00 
error of obfervation he has to contend ae arifing from the 
fufficient time allowed for examining the true pofition of the 
level and the accurate eins of the ftar. 
7 
The corrections to be applied fo the obfervations made 
with the repeating” circle “are, for the urpofe of reducing 
the meridian altitude, from that obferved a fhort time before 
or after the paflage of the far over the meiidian. The 
our angle, or diftance of the flar from the meridian, mutt, 
therefore, be correctly known ; and in proportion as the rate 
of the clock is well afcertained, may the obfervations be 
ag with confidence on each fide of the meridian. 
ole-{tar, from the flownefs aft its motion, benz the 
rom the oa beyon 
obfervations fhould never his table having been 
calculated for the ies of Paes e years fince, the 
numbers muft now -for the latitude re Cee ch be dimi- 
nifhed ,j,th, that is, the whale correétion multiplied by 
953 ‘aad for the inferior paflage of the flar the wholc 
correction muft be multiplied by 0.88. 
ables TL. and ILI. are general tables for any ftar, and 
for any latitude ; they were calculated by Delambre ‘from 
the following formula 
Let Pe The hour angle, 
L = Latitude, 
= ee of the ‘a 
rreétions required 
If the far pals lates be the zenith wx = 
2 fin.? 2 P, cof. D, colt n.t2P, cof, = 
fin. (Ls — D) fin, 1” = — L— D iin. 
cof. L — D fin. 1". 
~s 
- me the remainder of the calcula- 
fond is thus reduced to finding the value of the other fators, 
cof. D, cof. L cof. D, cof. L 
(Spo) Hand (FEE) cof D- L 
=i 
Example of an Obfervation of the Pole Star, by the repeating 
Circle. Bee 4th, 1807. ‘ 
vdvece . e 
Belo Qs 
Se oss 
RAé&SIO & 
, nw ” 
Te gol 8.5 
10 20] 6.9 
7 45) 3.8 
6 30) 2.7 | 147® 5! 50” 
3 0.6 
I 40] 0.2 
I 30] 0,2 
4 20) 1.2 | 294 11 00 
7 3-2 
8 40] 4.8 70 43 «58 
12 9-3 
16 30,175 | 81 16 54> Vernier, 
ere gy ee 5° = 
Sum 58.9 38 = 3 
60 = 4th 
