Professor Newton concludes that the third of the above-mentioned periods, viz., 354·62 days, combines the greatest amount of probability of being the true one. We grant the force of the reasons assigned for its adoption. At least one consideration, however, in favor of the long period of 33·25 years is by no means destitute of weight: of nearly 100 known bodies which revolve about the sun in orbits of small eccentricity, not one has a retrograde motion. Now if this striking fact has resulted from a general cause, how shall we account for the backward motion of a meteoric ring, in an orbit almost circular, and but little inclined to the plane of the ecliptic? In such a case, is not the preponderance of probability in favor of the longer period?
A revolution in 33·25 years corresponds to an ellipse whose major axis is 20·6. Consequently the aphelion distance would be somewhat greater than the mean distance of Uranus. It may also be worthy of note, that five periods of the ring would be very nearly equal to two of Uranus.
The Monthly Notices of the Royal Astronomical Society for December, 1866, and January, 1867, contain numerous articles on the star shower of November 13th–14th, 1866. Sir John Herschel carefully observed the phenomena, and his conclusions in regard to the orbit are confirmatory of those of Professor Newton. "We are constrained to conclude," he remarks, "that the true line of direction, in space of each meteor's flight, lay in a plane at right angles to the earth's radius vector at the moment; and that therefore, except in the improbable assumption that the meteor was at that moment in perihelio or in aphelio, its orbit would not deviate greatly from the circular form." The question is one to be decided by observation, and the only meteor whose track and time of flight seem to have been well observed, is that described by Professor Newton in Silliman's Journal for January, 1867, p. 86. The velocity in this case, if the estimated time of flight was nearly correct, was inconsistent with the theory of a circular orbit.
It is also worthy of notice that Dr. Oppolzer's elements of the first comet of 1866 resemble, in a remarkable manner, those of the meteoric ring, supposing the latter to have a period of about 33¼ years. Schiaparelli's elements of the November ring, and Oppolzer's elements of the comet of 1866, are as follows:
| November Meteors. | Comet of 1866. | |
|---|---|---|
| Longitude of perihelion | 56° 25′ | 60° 28′ |
| Longitude of ascending node. | 231 28 | 231 26 |
| Inclination | 17 44 | 17 18 |
| Perihelion distance | 0·9873 | 0·9765 |
| Eccentricity | 0·9046 | 0·9054 |
| Semi-axis major | 10·3400 | 10·3240 |
| Period, in years | 33·2500 | 33·1760 |
| Motion | Retrograde. | Retrograde. |
It seems very improbable that these coincidences should be accidental. Leverrier and other astronomers have found elements of the meteoric orbit agreeing closely with those given by Schiaparelli. Should the identity of the orbits be fully confirmed, it will follow that the comet of 1866 is a very large meteor of the November stream.
The researches of Professor C. Bruhns, of Leipzig, in regard to this group of meteors afford a probable explanation of the division of Biela's comet—a phenomenon which has greatly perplexed astronomers for the last twenty years. Adopting the period of 33¼ years, Professor Bruhns finds that the comet passed extremely near, and probably through the meteoric ring near the last of December, 1845. It is easy to perceive that such a collision might produce the separation soon afterward observed.
As the comet of Biela makes three revolutions in twenty years, it was again at this intersection, or approximate intersection of orbits about the end of 1865. But although the comet's position, with respect to the earth, was the same as in 1845–6, and although astronomers watched eagerly for its appearance, their search was unsuccessful. In short, the comet is lost. The denser portion of the meteoric stream was then approaching its perihelion. A portion of the arc had even passed that point, as a meteoric shower was observed at Greenwich on the 13th of November, 1865.[7] The motion of the meteoric stream is retrograde; that of the comet, direct. Did the latter plunge into the former, and was its non appearance the result of such collision and entanglement?
Fig. 3.
