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attentively. Meteoric showers composed principally of very small shootingstars are confined to the parts of the heavens immediately surrounding the radiant-point; while those consisting of large meteors spread far from the centre of divergence, the meteors (apparently from their brightness) being as plainly visible when they are seen by transverse as when they are seen foreshortened by very oblique vision. Meteor-showers of the former kind are called “contracted"; and of the latter kind “extended” (strett
larga). The foregoing are the principal terms employed by Professor Schiaparelli in describing the meteor-showers of which the positions of the radiant-points have now been published. The explanation of the phenomena of " diffuse” and “ multiple radiant-points is ingeniously supplied by Professor Schiaparelli in the following manner. A very small nebular mass of meteoroids or of cometoids baving been deflected from its original parabolic (or very excentric) into an orbit of moderate period round the sun by the attraction of some powerful planet in its path, the foremost and swiftest particles of the stream produced by this disturbance gradually gaining, and the slowest losing ground on the central particles of the mass, an elongated form of the mass is gradually assumed directed along the line of the meteoric orbit. The difference of velocity, or of periodic time, between the foremost and hindmost particles of the row is sufficient to ensure the gradual lengthening of the line, until the foremost particle joins with the last in forming a continuous ring or wreath of meteoric substance closing the orbit of the original meteoric cloud. Should the two ends, before meeting each other (as must usually be the case), have undergone different perturbations from the action of the planets, instead of exactly overtaking the retreating end, the foremost end of the wreath will overlap it, and the meteor-stream will begin to assume the form of a spiral curve of a single coil. When the foremost end has gained two revolutions upon the retreating one, a spiral of two coils will be produced; and continuing this process during many revolutions gained by one end of the coil upon the other, the wreath of meteoroids, without losing its continuity, will at last form an endless hoop, or belt, of many strands overlying and interlacing with each other in as many convolutions as the fastest particles have gained revolutions in their course upon the slower ones. The direction and velocity of the particles in one of the strands will also differ as widely as their positions from those of particles in a neighbouring strand, and the whole wreath, without ever losing its perfect continuity from end to end, will cross and recross itself in constantly going and returning waves. In these stages of transformation a meteoric stream would successively exhibit the characters of double and multiple radiant-points. Supposing the same process to con. tinue, and new perturbations of the stream to be constantly deflecting particles from the front or rear into different courses, these particles overtaking each other at the point where the earth passes through the stream would produce the mixed assemblage of radiant-points and of directions of the meteors of the August shower, which give it the character of multiple or of diffuse radiation. In the following list of radiant-points those marked with an asterisk (*) were described in the last Report (1870, p. 98); those at the end of the list are not included by Prof. Schiaparelli in his present list, which only represents the most important radiant-points observed, at present, in the first half of the year. In the cases where their identity with radiant-points in Heis's list, or in that of the British Association t, is suggested by Professor Schiaparelli, the position and duration of those radiant-points are added for comparison in the same columns of the Table.
| Report for 1868, p. 401 et seq.
List of the Principal Meteoric showers occurring in the first half of the year whose rad
points are derived from observations of shooting-stars in Italy, published in the Epheme of the Milan Observatory, for the years 1868, 1869, and 1870. By G. V. Schiaparel
II a. Jan. 6
[MG; Jan. 1-25... III b.
Contracted and ex- Observed in 1868 and 1869 Schiapar 175 +48 184 +28
Jan. 11, 1869
Jan, 12, 1869} 172 +311
Maximum Jan. 24............ R. P. Gre 187 +40 197 +59 Contracted and ex- Jan. 12, 1869 (traces on Jan. 11, Schiapara
1869), possibly a continuation of 232 +36 Most certain and A splendidly well-defined meteorexact.
shower. Jan. 18 (traces on Jan.
19), 1869. 198 +28
Jan. 19 (traces on the 18th), 1869. 220 +40
Many small meteors Jan. 19 (no
trace on the 18th), 1869.
apparently independent of II a,
Jan. 21 (no trace on 19th and 20th),
1869. Independent of the ra
diants IV d, VI a.
diffuse, perhaps nected with VI a, VI 6: see
the following Table (p. 48).
identical with the last ?)
perhaps multiple. shower on Jan, 28.
Extended ; confus- Jan. 28, 1868. ? If connected with
with the next.]
R. P. Greg fuse. 225 +34 Extended, uncer- Jan. 30, 1868. ?Connected with tain to 10°.
VIC, VI e; but no intermediate
meteors with IV a.
group with IV a, IV C, VI c and
VId: see following Table (p. 48). 134 +40 Few meteors Jan. 31, 1868. Traces on preced
ing evenings. Maximum Jan, 25-31
R. P. Gre
Contracted and ex- Feb. 3, 1869; a few traces on pre- Schiapareli
A few meteors only from the se-
with the next.
R. P. Gres] limited.
VII. Apr. 2–3 ...
1 II a.
Apr. 9 ...
WI c*. 'Apr. 11
Apr. 1-15 S. Apr. 20 V
Apr. 20 IX*. Apr. 14
gated radiant-re- o= +46° to a= 162° = +60°;
evidently identical with the next.
Mar. 31, 1868 Endures three days. Schiaparelli.
as a twin-radiant
with the next. 258 +36
Apr. 2, 1868) Distinct from but
may belong to the
Apr. 3, 1868 same family as Greg's 255 +36
Apr. 9, 1869 JQH, with centre near
# Herculis. 246 +46
Apr. 9, 1869. Twin - radiant with
the last. 163 +47
Apr. 10, 1869. Traces on Apr. 9.
?If connected with XXI b; no in
cent nights : belongs to the same
family as the two next. 185 +22
Heis. 199 + 14
Apparently belonging to the same Heis.]
family as XX c and XXI b. 167 +47
Apr. 14, 1868 and 1869. Connect- Schiaparelli.
ed by no meteors with XX c,
connection with any other me
teoric shower. 237 +35
Apr. 30, 1867 ) Apparently con
and 1868... nected or identical 237 +35
May 1, 1868 with the two next. 235 + 50
R. P. Greg.) 232 +27
vious evening some meteors from
direction of Vega (Zezioli).
or of the same system with the
R. P. Greg.)
į June 20.
Radiant-points contained in the former and omitted in the present list (see Report for 1870, p. 98.)
No. 6. Feb. 6.
12. Apr. 13 16. May 22 18. June 30
183 +56 231 +27 232 +25 240 +19
As many of the foregoing radiant-points, although separated from each other in position, or y nights in which no intermediate meteors were observed, nevertheless possess in common ome features of very close resemblance, they are regarded by Professor Schiaparelli as forming, in some cases, distinct meteor-systems or families of radiantpoints, of which the principal, occurring in the first half of the year, may be grouped as follows:
Families or groups of Radiant-points.
Should the effect of planetary perturbations, which retarded the return of Halley's comet in the year 1859 nearly one month from the time of its perihelion passage, as calculated by D'Alembert and Clairault, also explain the wide difference between the separate coils of spiral meteoric streams apparently encountered by the earth in the meteor-systems of which the above groups or families of radiant-points appear to present unmistakable examples, a new field of investigation in meteoric astronomy, and of future observation and research, is beginning to unfold itself in these new and interesting discoveries.
2. On Comets and Meteors, by Professor Kirkwood, Indiana University, U.S. (read before the American Philosophical Society, November 19, 1869). In an able treatise on “Meteoric Astronomy,” already noticed in these Reports (for 1868, p. 418), a short Appendix (B) at the end of the volume on “ Comets and Meteors” expresses the views on their connexion which Professor Kirkwood communicated, so long ago as July 1861, to the · Danville Quarterly Review' for December in that year. “ Different views are entertained by astronomers in regard to the origin of comets, some believing them to enter the solar system ab extra, others supposing them to have originated within its limits. The former is the hypothesis of Laplace, and is regarded with favour by many eminent astronomers.
Now, according to Laplace's hypothesis, patches of nebulous matter have been left nearly in equilibrium in the interstellar spaces. As the sun in his progress approaches such clusters, they must, by virtue of his attraction, move towards the centre of our system, the nearer portions with greater velocity than the more remote. The nebulous fragments thus drawn into our system would constitute comets; those of the same cluster would enter the solar domain at periods not very distant from each other. ... If we adopt Laplace's hypothesis of the origin of comets, we may suppose an almost continuous fall of primitive nebular matter toward the centre of our system—the drops of which, penetrating the earth's atmosphere, produce sporadic meteors, the larger aggregations forming comets. The disturbing influence of the planets may have transformed the original orbits of many of the former as well as of the latter into ellipses. It is an interesting fact that the motions of some luminous meteors (or cometoids, as, perhaps, they might be called) have been decidedly indicative of an origin beyond the limits of the planetary system. But how are the phenomena of periodic meteors to be accounted for in accordance with this theory?
* The division of Biela's comet into two distinct parts suggests several interesting questions in cometary physics. The nature of the separating force remains to be discovered; but it is impossible to doubt that it arose from the divellent action of the sun, whatever may have been the mode of operation. A signal manifestation of the influence of the sun is sometimes afforded by the breaking up of a comet into two or more separate parts, on the occasion of its approach to the perihelion'*. No less than six such instances are found distinctly recorded in the Annals of Astronomy, viz.:-1. Ancient bipartition of a comet.-Seneca. 2. Separation of a comet into a number of fragments, 11 B.C.—Dion Cassius. 3. Three comets seen simultaneously pursuing the same orbit, A.D. 896.—Chinese Records. 4. Probable separation of a comet into parts, A.D. 1618.—Hevelius. 5. Indications of separation, 1661.-Hevelius. 6. Bipartition of Biela's Comet, 1845–46.
“ In view of these facts it seems highly probable, if not absolutely certain, that the process of division has taken place in several instances besides that of Biela's Comet. May not the force, whatever it is, that has produced one separation again divide the parts ? And may not this action continue until the fragments become invisible ? According to the theory now generally received, the periodic phenomena of shooting-stars are produced by the intersection of the orbits of such nebulous bodies with the earth's annual path. Now there is reason to believe that these meteoric rings are very elliptical, and in this respect wholly dissimilar to the rings of primitive vapour which, according to the nebular hypothesis, were successively abandoned at the solar equator; in other words, that the matter of which they are composed moves in cometary rather than in planetary orbits. May not our periodic meteors be the débris of ancient but now disintegrated comets, whose matter has become distributed round their orbits ?”
These views, announced in the year 1861, were afterwards completely established by the calculations of Professor Newton and Professor Schiaparelli regarding the real orbital velocities of shooting-stars, proving them to move, generally, in parabolic, or cometic, rather than in planetary orbits; and by the astonishing discovery in the year 1866, by Professor Schiaparelli, of the almost absolute identity of the orbit of Tuttle's Comet (III. 1862) with that of the August, and of the orbit of Temple's Comet (I. 1866) with that of the November meteor-stream, supposing (as the researches of Professor Newton and Professor Adams amply prove) that the latter, and presumably also the former of those meteor-clouds revolve in elliptic orbits of such considerable length, as not to differ much from the comets in their times of revolution. In his communication to the American Philosophical Society, Professor Kirkwood retraces the recent researches of Hoek, Leverrier, and Schiaparelli respecting the probable circumstances of the introduction of comets and periodical shooting-stars ab extra into the limits of the planetary system. The disturbing force by which their cosmical orbits were converted into elliptic ones of short periods (it is found in harmony with the preceding theory) was probably the overpowering attraction of one of the larger planets near to which the cosmical bodies first entered the limits of the solar system.
* Grant's · History of Physical Astronomy,' p. 302. 1871.