ASTRONOMY: F. G. PEASE 
21 
in human blood. 6 It seems therefore conceivable that the high content of 
the non-protein nitrogen in the fish blood, accompanied by a slow circulation, 
might favor the deposition of waste products, and at the same time their 
slow removal would further tend to increase the accumulation. 
1 Donaldson, H. H., /. Comp. New., Wistar Inst., Philadelphia, 19, 1909, (155-167). 
2 Kellicott, W. E., Amer. J. Anal., Wistar Inst., Philadelphia, 8, 1908, (319-353). 
3 Donaldson, H. H., On the percentage of water in the brain of the summer flounder 
(Paralichthys dentatus) according to the body weight. MS. 1905. 
4 Scott, G. G., Proc. Soc. Exp. Biol. Med., New York, 9, 1912. 
5 Donaldson, H. H., /. Comp. Near., Wistar Inst., Philadelphia, 26, 1916, (443-451). 
G Hatai, S., Ibid., 28, 1917, (361-378). 
THE ROTATION AND RADIAL VELOCITY OF THE CENTRAL 
PART OF THE ANDROMEDA NEBULA 
By F. G. Pease 
Mount Wilson Solar Observatory, Carnegie Institution of Washington 
Communicated by G. E. Hale, December 27, 1917 
Indications of rotation in spiral nebulae are quickly obtained by means of 
spectrographs of very short focus and small dispersion, especially when a 
wide slit and devices for narrowing the spectrum are used. For definitive 
values of the rotation, however, it is necessary that the scale be relatively 
large, the slit narrow, and the exposures very long. 
To investigate the rotation of the great nebula in Andromeda, which had 
been reported by V. M. Slipher at the nineteenth meeting of the American 
Astronomical Society, an exposure of seventy-nine hours was made during 
August, September, and October, 1917, with the focal-plane spectrograph of 
the 60-inch reflector. This instrument which is used at the primary focus of 
the large mirror has a collimator of 135 mm. focus, a 60° prism of ultra-violet 
glass, and for the camera a 154 mm. Cooke lens. The dispersion is such that 
5.3 mm. corresponds to the interval from X 4930 to X 4950. The ratio of focal 
lengths of camera and collimator is 1.14, and the spectrograph therefore mag- 
nifies the image on the slit by this amount. 
TABLE 1 
DISTANCE FROM NUCLEUS 
NUMBER 
OF 
SECTIONS 
ADAMS 
MISS 
BURWELL 
MEAN 
seconds 
km. 
km. 
km. 
f 162 
1 
(-355) 
(-469) 
(-412) 
121 
2 
369 
400 
385 
South Prec. < 
66 
2 
342 
342 
342 
25 
1 
310 
312 
311 
0 
1 
307 
317 
312 
' 41 
2 
288 
308 
298 
North Foil. . 
96 
2 
278 
288 
283 
137 
1 
(292) 
(257) 
(274) 
