ASTRONOMICAL NOTES FOR AUGUST, 1881. 241 



Venus will be as visible as the morning star during the entire month ; on the 

 2d it will enter the northern part of Orion, passing from thence 'into Gemini on 

 the 6th, where it will remain until the 29th, then enter Cancer. It will be very 

 brilliant and may be seen in daylight; its position being about 3h west of the sun. 

 On the 20th it will be close to the moon. 



Mars will be in Taurus all the month. On the 17th it is 4° 42' north of 

 Aldebaran, the brightest star in the constellation. Its apparent motion is direct, 

 the mean daily increase in right ascension being 2 min. 40.8 sec, and in north 

 declination 7' 12". It is slowly approaching the earth and increasing in apparent 

 size. On the 15th it will rise at 11 h. 33 m. P. M. 



Jupiter, the giant planet of this system, will rise about 11 o'clock P. M., and 

 attended by its four satellites will present some interesting phenomena to those 

 possessed of a small telescope, or a good opera glass. The satellites of this planet 

 are the most difficult members of the solar system, for the mathematician to'calcu- 

 late, /. e. to find how much the attraction of one will affect the position of the 

 others. The effect may be understood from the following laws : 



I St. That the mean motion of the first satellite added to twice the mean motion of 

 the third, is exactly equal to three times the mean motion of the second. 



2nd. That if to the mean longitude of the first satellite we add twice the mean 

 longitude of the third, and subtract three times the mean longitude of the second, the dif- 

 ference is always 180°. 



The following is a list of their eclipses and prominent phenomena visible at 

 Kansas City during the month : On the 4th at 00 h. 05 m. 04 s. A. M., lo, the 

 one nearest to Jupiter, will disappear in echpse. The same occurs again on the 

 nth at I h. 58 m. 48 s. A. M. 



Europa, the next in order of distance from Jupiter, will reappear after an 

 eclipse on the 15th at 00 h. 57 m. 44 s. A. M., and remain visible fifteen minutes 

 and disappear in occultation behind the disk of the planet. On the 2 2d at 3 h. 

 33 m. 55 s. A. M., it likewise reappears, remains visible fourteen minutes and 

 disappears. On the 29th at 3 h. 37 m. 51 s. A. M., it disappears in eclipse and 

 does not reappear before daylight. 



Ganymede, the third in distance from the planet, on the 14th at i h. 44 m. 

 A. M., will appear after occultation and on the 21st at 00 h. 11 m. 29 s. A. M., 

 it will reappear after an eclipse; it also disappears in eclipse on the 28th at 2 h. 

 37 m. 08 s. A. M. 



The orbit of Callisto, the fourth satellite, is so much inclined to the ecliptic 

 that it does not get eclipsed or occultated this month. 



Saturn, on the ist will rise at 11 h. 17 m. P. M., and on the 31st at 9 h. 

 21 m. P. M. On the 24th its position among the stars will remain fixed for a 

 short time, owing to the earth moving in a straight line toward it. The appar- 

 ent elements of its rings are as follows: Diameter of outer major axis 42.67", 

 minor axis 14.72", inclination of the northern semi-minor axis to the circle of de- 

 clination from north to east 34.3', the elevation of the earth above the plane of 

 the southern surface of the ring 20° 10.6', elevation of the sun 18° 29.9', earth's 



V— 16 



