4 
ASTRONOMY: SEARES, VAN MAANEN AND ELLERMAN 
katabolism of different species of animals is substantially proportional to 
their body surface. It may be surmised that the exceptional result with the 
hog is due to the imperfect data available for computing the body surface 
of this species. 
1 Armsby, Washington, D. C, U. S. Dept. Agric, Bur. Anim. Indust., Bui. 142, 1912. 
2 Armsby and Fries, Ibid., Bui. 128, 1911. 
3 Armsby and Fries, /. Agric. Res., Washington, 3, 1915, (435); 10, 1917, (599); 11, 1917. 
4 Moulton, /. Biol. Chem., New York, 24, 1916, (299). 
5 Benedict, Emmes, Roth and Smith, Ibid., 18, 1914, (139). 
6 Means, Ibid., 21, 1915, (263). 
7 DuBois and DuBois, Arch. Inter. Med., 15, 1915, (868). 
8 Meissl, Strohmer and Lorenz, Zs. Biol., Miinchen 22, 1886, (63). 
9 Tangl, Biochem. Zs., 44, 1912, (252). 
10 Fingerling, Kohler and Reinhardt, Landw. Versuchstat, Berlin, 84, 1914, (149). 
11 Zuntz and Hageman, Landw. Jahrb., Berlin, 27, 1898, Ergzbd. Ill, (284). 
12 Voit, E., Zs. Biol., Miinchen, 41, 1901, (113). 
THE LOCATION OF THE SUN'S MAGNETIC AXIS 
By F. H. Seares, A. van Maanen, and F. Ellerman 
Mount Wilson Solar Observatory, Carnegie Institution or Washington 
Communicated by G. E. Hale, November 26, 1917 
The discovery by Mr. Hale in 1913 of a general magnetic field 1 surrounding 
the sun raised at once questions of great interest. First among these was the 
character of the field and the variation of its intensity over the solar surface. 
A preliminary investigation showed that approximately the sun may be re- 
garded as a uniformly magnetized sphere, its axis coinciding with the axis of 
rotation. The minuteness of the observed quantities and the difficulties ex- 
perienced in their measurement necessitated the provisional acceptance of 
this simple hypothesis; nevertheless, well-known peculiarities of the earth's 
magnetic field suggested that the solar field might deviate from that of a 
spherical magnet, and that its axis might be inclined to the rotation axis by an 
amount susceptible of measurement by special series of observations. This 
communication is concerned with the latter of these questions, namely, the 
position of the magnetic axis. 
Observations of the sun's field are made by placing the slit of the spectro- 
graph in coincidence with the central solar meridian. A compound quarter- 
wave plate and a Nicol prism just outside the slit serve as an analyzer, the ob- 
served effect being a minute displacement of an appropriately chosen spectral 
line. The amount of the displacement varies with the inclination of the lines 
of force to the line of sight, in other words, with the position of the sun's 
magnetic axis, the heliographic latitude of the point observed, and the dis- 
