398 REPORT—1868. 
of the earth was not so easily computed, owing to the intersection of the two 
orbits. An approximate solution applicable to this case showed, however, 
an annual increase of the longitude of the node of about 10” due to this 
cause. The whole computed procession of the node was therefore about 21” 
a year, or 12’ in the cycle of 33°25 years. 
‘The periodic time 376-6 days gives a result not widely different from the 
above, while in the two smaller orbits there would be a much smaller motion. 
Hence these four orbits, out of the five possible ones, are incompatible with 
the observed motion of the node. 
‘«‘ Computing, then, the effect of the perturbing action of the planets upon the 
group, supposing it to have a periodic time of 33:25 years, Prof. Adams found 
that Jupiter increases the longitude of the node 20' in one revolution, that 
Saturn increases it 7', and Uranus increases it 1’; the other planets produce 
hardly any sensible effect; so that the entire calculated increase of the lon- 
gitude of the node in the period of 33°25 years is about 28’. The observed 
increase during the same time is 29’. This remarkable accordance between 
the results of theory and observation appears to leave no doubt as to the cor- 
rectness of the period of 33°25 years.” 
Supposing a meteor-current to be the regular concomitant of a comet, 
whose presence on the same orbit with the comet can only be perceived at a 
point of encounter with the earth, a list of those comets whose orbits most 
nearly approach the orbit of the earth, was prepared by Dr. Weiss, of Vienna, 
(Astron. Nachrichten, No. 1632). The distance of such a comet from the 
sun in the ecliptic (r), at the place of its ascending (§) or descending 
node (8), is nearly equal to the earth’s distance (supposed unity) from the 
sun at the instant of its nodal passage through the plane of the comet’s orbit. 
The following list contains the data thus obtained by Dr. Weiss. 
Date of Nodal Comet. Node. r. Remarks. 
Shower. passage. 
Jan. 1-4JJan. 3.) II. 1792 8 0-983 
1- 4. 4.) IV. 1860 8 | 0:985 
18-20. 18. 1672 8 1:046 
18-20. 20.) I. 1840 R 0-948 
28. 26. 1092 8 0-977 
Feb. 13-14./Feb. 13.) IV. 1854 3 0-973 
13-14. 14.| IV. 1858 3 0-973 
Mar. 5-10.)Mar. 8.| III. 1854 8 1-025 
5-10. 8. 1490 9} 0:960 
5-10. 13. 1683 8 1:047 
16-20. 16. 1763 3 1:020 
16-20. 16.| IV. 1862 83 0-982 
Apr. 16-25.|Apr. 16.) I. 1830 8 0-923 
16-25. 1% 837] 8 1:026 | Very uncertain orbit. 
16-25. 20.;' I. 1861 8 1:003 | P = 415 years. 
16-25. 22.| II. 1748 3 0-886 
16-25. 24,| ITT. 1790 8 1-052 
May 18-26.) — —_— _ — 
July 27-30.|July 27.| Il. 1737 8 9:995 
Aug. 7-13.|Aug. 9.| IT. 1852 8 1:025 
7-13. 9.| IIT. 1862 8 1:019 | P= 113 years. 
16-20. 19.| II. 1862 8 1-039 
