A^D A SELECTION EEOM THE OBSEEVATIONS MADE WITH THEM. 
741 
\_Observafions of Stars in the Spiral Nebula. H. 1622. 
The spiral form of this nebula is very distinctly seen in the Pulkova refractor. Un- 
fortunately in the month of March, the best season for the observation of this object, 
the sky was constantly cloudy ; so that I could only get three nights’ observations in the 
months of April and May, when the twilight did not cease for the whole night. It 
must be attributed to this unfavourable circumstance that the following list of determi- 
nations is not so complete as it probably would have been without the twilight. The 
observations have been made alternately with powers of 138 and 207. 
Observations. 
1 Date. 
Object. 
Magnitude. 
Ang. Pos. 
No. of 
measures. 
Distance. 
No. of 
measures. 
1851, April 7* 
N/i 
14 55 
5 
267-1 
4 
N a 
a =(11) 
229 24 
3 
88-0 
3 
N6 
b =(11.12) 
109 12 
3 
242-6 
3 
a b 
93 42 
3 
298-6 
3 
April 28. 
a b 
94 23 
3 
300-8 
4 
Na 
228 36 
4 
N6 
108 54 
4 
n a 
203 42 
3 
n b 
153 30 
3 
a d 
d =(12.13) 
323 51 
3 
Nc/ 
277 27 
3 
a e 
e =(13) 
112 13 
3 
Ne 
161 56 
3 
N/ 
/ =(12.13) 
309 18 
3 
237 31 
3 
335 23 
3 
ug 
9 =(12.13) 
215 17 
3 
115-5 
4 
a h 
h =(12.13) 
193 29 
3 
gh 
87 5 
3 
May 3. 
N/e 
k =(13.14) 
51 47 
3 
n k 
173 29 
4 
bk 
317 23 
3 
bl 
1 =(11.12) 
27 20 
4 
n 1 
83 17 
4 
355-2 
4 
a e 
112 56 
4 
Ne 
I6l 39 
3 
a m 
m =(12.13) 
172 43 
5 
N m 
190 44 
4 
b m 
238 50 
4 
Na 
229 12 
4 
87-0 
3 
N n 
14 47 
4 
264-2 
3 
The results of these measures were deduced in this way, that I first fixed the rela- 
tions between the four principal objects, namely, the centres of the two nebulae N and 
n, and the two brightest stars a, b. In the triangle N « 5, all distances and directions 
have been measured It is therefore over-determined, and the definite relations had 
to be deduced by the calculus of compensation. This calculus gives — 
Ang. Pos. 
Distance. 
Na 
229 26 
// 
88-57 
N6 
108 54 
243-63 
a h 
94 6 
298-55 
