20 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



distance of Venus. If so, it explains the fact that the edge 

 of the dark limb of Venus is seen brighter than its central 

 part ; for it is demonstrable by calculation and confirmed 

 by observations that a rough surface reflecting diffused light 

 appears the brighter the more obliquely it is regarded. 

 Report Brit. Assoc, 1873, 408. 



THE TIDAL RETARDATION OF THE EARTH'S ROTATION. 



In some remarks on the various causes that operate to 

 retard or accelerate the earth's daily rotation, Mr. Mallet 

 remarks that if we take into account all the operations at 

 work upon the earth's surface, such as the flowing of rivers 

 down hill into the ocean, the carriage of great masses of 

 earth, as mud, from the upper sections of the earth to the 

 bottom of the ocean, the fall of raindrops, the flow of rivers 

 from low to high latitudes, and all other similar seemingly 

 insignificant causes, we shall find no reason to suppose that 

 the retardation of our globe by tidal friction, whatever may 

 be its actual amount, can go on unchecked until the earth 

 is brought to a stand. 7 A, XLVIL, 40. 



THE MASS OF JUPITER. 



Powatky has attempted a new determination of the mass 

 of the planet Jupiter, by examining its perturbing influence 

 on the movements of the asteroid Virginia (No. 50). The 

 result to which he is led indicates that the mass of Jupiter 

 should be increased by about one two-hundred and seventy- 

 second part of the present adopted value ; but although this 

 correction enables him more nearly to satisfy the observa- 

 tions that have been made upon Virginia, he is yet inclined 

 to attribute to it only a slight value, and hopes to attain 

 better results by a repetition of his work in future years. 

 Astron. Nach., LXXXIV., 71. 



THE SATELLITES OF URANUS. 



An interesting study has lately been made by Professor 

 Holden,of the Washington Observatory, on the observations 

 of Sir William Ilerschel upon the satellites of Uranus. It 

 is well known that the latter astronomer announced sixty 

 years ago that Uranus was accompanied by six satellites; 

 but of the existence of four of these there has always been 



