,30 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



-=-(2 1)], and gives the ninth verification to his harmonic 

 prediction. Gaillot 0.1803; Chase 0.1826." 



Till-: PLANETS AND SATELLITES. 



Jfercury. The principal observations of Mercury arc 

 spoken of under the heading Transits of Mercury. 



Venus. M. Boutigny has called the attention of the 

 French Academy to the fact that Varro (31 B.C.) spoke of 

 changes in the diameter, color, figure, and path of Venus. 

 The passage referred to is quoted in a work of St. Augustine. 

 Venus has been observed during the last year with the 26- 

 inch Washington equatorial. No markings on the disk were 

 seen, but the illumination of the dark hemisphere was fre- 

 quently noted by several observers. 



Mars. From the recent discussion by Professor Hall of his 

 observations of the satellites of Mars, we extract the follow- 

 ing : " The planes of the orbits of both satellites are very near- 

 ly coincident with the equator of Mars. The elements of 

 these orbits are determined with tolerable accuracy, except- 

 ing the periodic times, for an accurate determination of which 

 we must wait until the satellites have been observed in an- 

 other opposition. The times that have now been found will 

 serve to carry forward an ephemeris to 1879. In the orbit 

 of Deimos, the value of the eccentricity being small, the posi- 

 tion of the line of apsides is of course uncertain. This eccen- 

 tricity is so small that circular elements of this satellite may 

 be considered as sufficient for the observations. In the case 

 of Phohos, the eccentricity of its orbit has, I think, a real ex- 

 istence. It will be noticed that in the comparison of the 

 observations of PJiobos with the assumed circular elements, 

 every comparison of distance confirms the existence of an 

 eccentricity. It is true that the observations of this satellite 

 were always difficult on account of its closeness to the planet, 

 and also because of the brightness of the planet; and it may 

 be suspected that some systematic error has influenced the 

 result. Such an error would indeed have more influence on 

 the eccentricity of the orbit of the inner satellite than on that 

 of the outer one. But the resulting eccentricity is too large, 

 I think, to be explained in this manner, and I conclude that 

 the orbit of Phobos is really eccentric." 



The mass of Mars can be determined from the motion of 



