KNoWhKIKiK. Maikii LM, 1882.] 



THE PATH OK MARS 



LOOPED PATH OF A PLANICT. 

 Bv TiiK EniToit. 



MANY even of thoso who liavo read 

 tho usual descrijitioiis of planetary 

 motions, in our text-liooks of astronomy, 

 are perplexed by the way in wliieh the 

 planets pursue 



Tlieii- waiuloriiig course, now lii,-!i, now low, 

 tlioQ hid, 

 I'leigrossivo, retroffrnde, uiul standing; still. 



Miirs, Jupiter, and Saturn, during the 

 la.st few months have givpn Ktrikin<» illus- 

 trations in the skies (as indieated in our 

 maps) of their strange, and at first view, 

 fantastic and irregular motion.s. ^lai-s, in 

 particular, traverses a singularly devious 

 course upon the hackground of tho starlit 

 heavens. It has seemed to mc that it 

 would be interesting to exhibit the real 

 course of this ]ilanet, the one of all the 

 sun's family wliose j)ath, with reference 

 to the earth, has the most complicated 

 form. Of course, in reality this planet 

 travels around the sun in an ellipse 

 which is almost circular in form, though 

 considerably eccentric in position. The 

 earth also pursues an elliptic path, smaller 

 in size, still more nearly circular in form, 

 and much less eccentric. But viewed 

 from the earth, the planet Mars, in con- 

 sequence of the combination of these two 

 circling (but not strictly circular mo- 

 tions), travels on such a looped path as 

 is shown in the accompanying map. Here 

 the planet's position, as \'iewcd from the 

 earth (his geocentric position, as it is 

 called), at the successive oppositions (or 

 times of nearest aj)proach to the earth), 

 is shown V)y the small dot at the end of 

 the dated radial line. Then, at succes- 

 sive intervals of ten days, measured for- 

 ward and Viackward from the time of 

 opposition, Mars has the positions in- 

 dicated by the successive dots. (Of 

 course, there is a place in the outermost 



