MKMi>li;s OK TIIK NATIONAL A(AIM;.MY OF SCIKNCKS. 23 



I'licouiitors with Jiipitcr. Alter sii(lii-liaiij;ostlios(<c<>iiu'ts must lie rcjiiinlcd as t<»k'r:il)lyiii'nn!iin'iit 

 ini'iubin's of the solar sysU-iii. 



17. Comets tliat have inotioiis not greatly inclined to .Inpitor's niotidu, arc, as Figs. 2 ami 1 

 sliow, more likely in subse(inent passages near to .Iui)iter to have their periodic times shortemil 

 than leniithened. Dn tlie eonlraiy those passing in neaily opposite direction to Jupiter's motion 

 will as I'igs. .'5, 5, and 7 show, he nnnrh more likely to iiase theii- periods lengthened than short<'ne<l. 



All these oanses combine and work together t4i the one end that those comets which arc 

 changed by the perturbing iietion of Jupiter, or other planets, fr(un parabolic orbits of every 

 lM)ssible iueiiuatiou to the oclii)tie into sliort period ellipses and become ]termanent members of 

 the solar system, will as a rule (but with exceptions) move in orbits of moderate inclination to the 

 ecliptic, and with direct motions. 



We know as a fact that uu)st sln)rt period comets do move in orbits having small inclinations 

 and direct motions, while long period and iiarabolic comets move atalljiossible inclinations to the 

 eclii)tic. If the short i)eriod conu'ts have been changed by Jupiter and other jilanets from parabolic 

 orbits, the preceding investigation shows why their orbits have now small iiu'linations to tiie 

 ecliptic, and the comets themselves have direct motions. 



