1. Encke's 4.09 2. 1819 IV 4.81 3. De Vico's 5.02 4. Pigott's (1783) 5.28 5. 1867 II 5.29 6. 1743 I 5.32 7. 1766 II 5.47 8. 1819 III 5.55 9. Brorsen's 5.64 10. D'Arrest's 5.75 11. Faye's 5.93 12. Bicla's 6.19 =II.= COMETS WHOSE APHELION DISTANCES ARE NEARLY EQUAL TO 9.54, THE RADIUS OF SATURN'S ORBIT. Comets. Aph. Dist. 1. Peters' (1846 VI.) 9.45 2. Tuttle's (1858 I.) 10.42 =III.= COMETS WHOSE APHELION DISTANCES ARE NEARLY EQUAL TO 19.18, THE RADIUS OF URANUS'S ORBIT. Comets. Aph. Dist. 1. 1867 I 19.28 2. November meteors 19.65 3. 1866 I 19.92 =IV.= COMETS WHOSE APHELION DISTANCES ARE NEARLY EQUAL TO 30.04, THE RADIUS OF NEPTUNE'S ORBIT. Comets. Aph. Dist. 1. Westphal's (1852 IV.) 31.97 2. Pons' (1812) 33.41 3. Olbers' (1815) 34.05 4. De Vico's (1846 IV.) 34.35 5. Brorsen's (1847 V.) 35.07 6. Halley's[10] 35.37 [10] Halley's comet _in aphelio_ is too remote from the plane of the ecliptic to be much disturbed by Neptune. Has the original position of the orbit been changed by Jupiter's influence? The coincidences here pointed out (some of which have been noticed by others) appear, then, to be necessary consequences of the motion of the solar system through spaces occupied by meteoric nebulæ. Hence the observed facts receive an obvious explanation. In regard to comets of long period we have only to remark that, for anything we know to the contrary, there may be causes of perturbation far exterior to the orbit of Neptune.