A. MATHEMATICS AND ASTRONOMY. 19 



the moon. Zollner also makes a very ingenious attempt 

 to determine the albedo of the earth, and the law of the 

 variable intensity of the light that will be exhibited by it, 

 in its various phases, as seen from a distant planet. Con- 

 cerning his attempt to determine this albedo through ob- 

 servations of the dark limb of the moon, he states that, al- 

 though the results can scarcely be accepted as having much 

 accuracy, they nevertheless show the practicability of the 

 method. 19 (7, 1874, 150. 



THE ATMOSPHERE OF VENUS. 



Lohse has investigated what would be the effect and ap- 

 pearance of a spherical gaseous mass passing over the solar 

 disk as seen from the earth, and has sought to apply his re- 

 sult to the possible effect of the atmosphere of Venus on 

 the phenomena of the Venus transit. In conclusion, he 

 states, with reference to the so-called black-drop phenom- 

 enon, that if the atmosphere of Venus has a density so 

 great that it unites the solar rays in one point lying be- 

 tween Venus and the earth, it must then have the same 

 effect as an opaque body that is to say, the solar limb 

 will by this atmosphere be broken or indented before the 

 body of Venus itself touches it ; and, conversely, the solar 

 limb will not regain its integrity, at the close of the inner 

 contact, until the atmospheric layer is entirely within the 

 solar disk. It is possible that, at the inner contact, this 

 effect of the atmosphere of Venus contributed considerably 

 to the appearance of the so-called black drop. 19(7,1874, 

 170. 



THE VISIBILITY OP THE PLANET VENUS. 



Professor Safarik, of Prague, endeavors to explain the 

 intense brightness of Venus, and particularly the dazzling 

 splendor of her bright limb, without assuming specular re- 

 flection on the surface of the planet. He remarks that the 

 intensity of the phosphorescence of the sea in our tropical 

 waters is not fully appreciated by the near observer, who 

 therefore has only a faint idea of the intensity which this 

 phenomenon can acquire under highly favorable circum- 

 stances, and the author thinks it not unreasonable to sup- 

 pose that such a phosphorescence can be seen even at the 



