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that the axis of rotation is intermediate between the two positions in which the slit was placed across the nebula. For the portions of the line originating in the rings and central part of the nebula, no simple rotational hypothesis alone seems competent to explain the complex form of line obtained.
The nebula is a very irregular and patchy oval (about 54"X20"). Two bright masses appear near the center, about 7 seconds apart. The last spectrogram was taken with the slit along the line joining these two nuclear masses, which is approximately the shorter axis of figure of the large oval. The N, line is broad and hazy, and appears somewhat curved, with the concavity toward the violet. In the direction of the longer axis the nebula is too faint to permit of obtaining a high-dispersion spectrogram with practicable exposure time.
N.G.C. 2452. a = 7h 43^4; 8 = —27° 6'; A = 125° 2'; p = -47° 27' The determination of the radial velocity of this object seems to present some difficulties. The nebula is faint, and we cannot be sure that the slit is uniformly or symmetrically illuminated. There are some suggestions, from Dr. Curtis's illustration, that the nebula is in rapid rotation: the elongated elliptical outline of the very faint disc and the faintness of the disc near the extremities of its major axis, as in the case of N.G.C. 7026, R.A. = 2P 3m. The observed radial velocities would in that case be sensitive to the region falling in the slit. The discrepancies in the observed velocities quoted below may have their explanation in those facts. The lines are crooked and irregular.
On the, spectrogram of fi'-f>fmb^r Ifi. lf>17. the crooked N', line indicates a relative velocity of the north half of nebula with respect fo The south half of —28 lrm.
Our observations will he harmonized fairly w^ll if we assume that the equator of the ellipsoidal nebula is in position angle about, 60'', and that the southwest edge of the nebula is relatively approaching by virtue of rapid rotation of the object.