ASTRONOMY: H. N. RUSSELL 
77 
known. Two sets of values are given for Mercury, corresponding to 
the two empirical formulae for the variation of its brightness with phase 
given by Miiller, and four for the earth, representing the results derived 
from Very's observations on the assumption that the variation of the 
brightness of the earth with phase follows four different laws, derived 
from theory or from observation of other bodies. 
10. These values of the albedo of the various bodies are in entire 
agreement with the current views of their constitution. For Venus and 
the outer planets, which are generally supposed to be covered with clouds, 
the albedo is very near the value found by Abbot for terrestrial clouds 
(0.65). For Mars, Mercury and the moon the albedo is comparable 
with that of ordinary rocks, as it is also for three of the four asteroids. 
Even the high value for Vesta can be matched by some whitish terrestrial 
rocks; but the still higher values for the inner satellites of Jupiter are 
rather remarkable. 
11. The value here found for the earth's albedo is intermediate be- 
tween those of the cloudy and cloudless planets, and agrees very closely 
with Abbot's estimate^ of 0.37, based on the known cloudiness of the 
earth's atmosphere. It is only half as great as that which Very has 
derived from the same observations, but the discrepancy is easily 
explicable. The discussions of the observations by Very and by the 
writer agree in showing that the albedo of the earth (more precisely, 
the value of the constant called p above) is a little more than five times 
as great as that of the moon (if Zollner's value for the brightness of the 
latter is adopted). But the value of the moon's albedo used by Very 
(0.174) is what Zollner^ calls the ^'true albedo" — which is the value 
obtained after a large and very uncertain correction for the assumed 
influence of the irregularities of the surface, according to a theory which 
has later been found to contain a serious error.^^' Zollner's observations 
themselves lead to the value 0.080 for p, and when this correction is 
made, the discrepancy disappears. 
The full paper, with much more extensive references, will be published 
in the Astro physical Journal. 
1 Proc. Amer. Acad. Arts Set., 8, 232 (1861). 
. 2 Results of Astronomical Observations made at the Cape of Good Hope (London, 1847), pp. 
353-374. 
^Potsdam Pub. Astrophysik., Bd. 8, Tl. IV (1893). 
* Harvard Coll. Obs. Cir., No. 169 (1911). 
5 Astr. Nachr., 198, 251 (1914). 
« Ann. Obs. Harvard Coll., 59, 261-264. 
7 Astr. Nachr., 196, 269-290 (1912). 
* Smithsonian Inst., Ann. Astrophys. Obs., 2, 161-163. 
^ Photometrische Untersuchungen (Leipzig, 1865), p. 162. 
" See Miiller, Photometric der Gestirne (Leipzig, 1897), p. 77. 
