416 
ASTRONOMY: H. N. RUSSELL 
59 Shapley, H., Astrophys. Jour., 48, 1917-18, (89-124, 154-181). 
eoTrumpler, R., Pop. Astron., 26, 1918, (9). 
61 Leavitt, Miss H., Harvard Circular, 173, 1912. 
62 Shapley, H., Astrophys. Jour., 48, 1918, (155). 
63 Wilson, R. E., Pub. Ast. Soc. Pacific, 27, 1915, (86). 
64 Fowler, A., Monthly Not. Roy. Ast. Soc, 77, 1917, (516). 
65 Fabry, Astrophys. Jour., 40, 1914, (256). 
66 Wood, R. W., Physical Optics, 2d ed. (New York, 1911), p. 583, 
67 Fabry, Astrophys. Jour., 45, 1917, (269-277). 
*8 Slipher, V. M., Lowell Observatory Bulletin, 2, 1912, (24). 
69 Hertzsprung, E., Ast. Nach., 195, 1913, (449). 
70 Slipher, V. M., Lowell Obs. Bull., 3, 1918, (63). 
71 Bannard, E. E., Astrophys. Jour., 49, 1919, (1). 
. 72 Slipher, V. M., Lowell Obs. Bull., 2, (155). 
73 Campbell, W. W., Pub. Ast. Soc. Pacific, 29, 1916, (284). 
74 Campbell, W. W. and Moore, J. H., Ibid., 27, 1915, (240). 
75 Fabry, Astrophys. Jour., 40, 1914, (241). 
76 Slipher, V. M., Pop. Astron., 23, 1915, (23). 
77 Slipher, V. M., Lowell Obs. Bull., 2, 1914, (66). 
7^ Young and Harper, Jour. Roy. Ast. Soc Canada, 10, (134.) 
79 van Maanen, A., Astrophys. Jour., 44, 1916, (210-228). 
80 Kostinsky, S., Monthly Not. Roy. Ast. Soc, 77, 1917, (233). 
81 Seares, F. H., these Proceedings, 2, 1916, (553). 
82Eddington, A. S., Monthly Not. Roy. Ast. Soc, 77, 1916-17, (16 and 596); also ^4^- 
trophys. Jour., 48, 1918, (205). 
83 Jeans, J. H., Observatory, 40, 1917, (60). 
84 Schwarzschild, K., Astron. Nach., 190, 1912, (361), and 198, 1914, (217). 
85 Jeans, J. H., Monthly Not. Roy. Ast. Soc, 76, 1915-16, (70 and 552). 
86Eddington, A. S., Ibid., 74, 1913, (5), and 75, 1916, (366), and 76, 1916, (37). 
87 Eddington, A. S., Ibid., 76, 1916, (572-585). 
88 Eddington, A. S., Ibid., 79, 1918, (2). 
89 Nolke, F., Abh. Nat. Ver. Bremen, 20, Teil 2, 1911, (193-220). Jeans, J. H., Ohser- 
vatory, 42, 1919, (40). 
90 Shapley, H., Pub. Ast. Soc Pacific, October, 1918, (283-298). 
91 Eddington, A. S., Monthly Not. Roy. Ast. Soc, 79, 1918, (19). 
92 Abbot, G. G., these Proceedings, 4, 1918, (104-106). 
93 Nicholson, J. W., Monthly Not. Roy. Ast. Soc, 76, 1916, (415); 78, 1918, (349), and earlier 
papers. 
94 deSitter, W., Ibid., 78, 1917, (25). 
95 As this paper goes to press, van Maanen, {Pub. Ast. Soc Pacific, 31, 1919, (42) ) an- 
nounces the discovery of a star of type F, and absolute magnitude 14.3 on Kapteyn's scale. 
If the surface brightness of this object has the value which is ordinarily associated with its 
color and spectrum, its diameter must be comparable with that of the Earth. These faint 
stars are evidently going to present a problem of great interest and difficulty. 
