[73] Chapter VI, [p. 99].

[74] Chapter IX, [p. 137].

[75] Shapley, H. B. 805, 1924.

[76] Chapter XIII, p. [p. 188].

[77] Chapter V, [p. 56].

[78] Ap. J., 59, 197, 1924.

[79] Eddington, Zeit. f. Phys., 7, 371, 1921.

[80] Russell and Stewart (loc. cit.) show that there are about 0.4 grams of matter above the photosphere per square centimeter of surface.

[81] Phil. Mag., 26, 9, 1913.

[82] Phil. Mag., 37, 456, 1919.