AND A SELECTION FEOM THE OBSEEVATIONS MADE WITH THEM. 
743 
Designation 
by Lord Rosse. 
Designation 
by 0. Struve. 
Ang. Pos. 
S-R. 
Distance. 
S-R. 
N n 
N n 
1^ 34 
o / 
-1 43 
4 22-2 
// 
+ 3-4 
N 1 
NA 
62 4 
-0 17 
2 6-6 
— 11*5 
N 2 
N 3 
N 4 
N6 
54 0 
104 20 
111 57 
— 3 3 
5 0-0 
2 45-6 
4 3-6 
00 
N 5 
Ne 
165 35 
—3 48 
1 43*2 
+ 1-2 
N 6 
N m 
191 42 
-1 18 
3 54-0 
+ 16-0 
N 7 
NA 
211 2 
-0 11 
2 36-6 
+ 17-6 
7, 8 
hg 
270 42 
—3 37 
0 34-8 
+ 9-9 
N 9 
Na 
231 32 
-2 6 
1 23-4 
-H 5*2 
9, 10 
N 11 
Nrf 
197 57 
279 21 
-1 54 
0 27-0 
1 49-8 
+ 12-1 
11, 12 
N 13 
14, 15 
N 15 
N/ 
225 27 
281 37 
297 15 
310 34 
-1 32 
0 12-6 
3 51-0 
2 55-8 
+ 14*1 
From this comparison it is evident that all angles measured by Lord Rosse are too 
great. The mean value of the correction, 1° 57', corresponds to a linear distance of 
— 4"’7. TTie distances appear to be generally too small. The mean value of the 
differences is +6"- 8 . Perhaps Lord Rosse’s star 2 is identical with my 1; but in that 
case, Lord Rosse’s distance N 2 must be an error of writing. At the distance of 
6' from N I could not see the least trace of a star in the indicated direction. In my 
copy of Lord Rosse’s diagram the star 2 is placed at a distance of about 8', correspond- 
ing with my observations; 10 appears to me only as a knot of the nebula, and has 
therefore not been measured by me. About the stars 3, 12, 13, and 14 there is no 
notice given in my journal. Perhaps they might be seen and measured with our 
refractor. The next spring I intend to repeat and to complete the series of observa- 
tions, and to decide on the visibility of the not yet noticed stars. 
(Signed) Otto Struve. 
(Dated) Pulkova, June 2, 1851.] 
In forming some estimate of the degree of reliance to be placed on the micrometrical 
measurements in this paper, we have taken advantage of the information so obligingly 
communicated by M. O. Struve. 
As to the measures of distance, they accord with Struve’s as closely perhaps as could 
be expected. We measure with bars instead of lines, and without illumination, that 
we may the better see the faint details of the outlying portions of the nebulae ; besides, 
we do not employ clockwork to move the telescope. Our measures of stars cannot 
therefore in accuracy compete with Struve’s, but they are quite sufficient for giving 
precision to the drawings. As to the angles of position, the same remarks apply, with 
this addition, that we refer our measurements to the horizon, and reduce them to the 
equator. Our zero is therefore obtained from the spirit-level, which saves time, to us a 
great object. We proceed in this way: the level is made horizontal and read off: each 
MDCCCLXI. 5 H 
