901 to 9301 period of 29.000 years.930 to 157122 periods of 29.136 "1571 to 18339 periods of 29.111 "1833 to 18621 period of 29.000 "
Meteors of October 16-20.
Meteoric showers were observed from the 16th to the 20th of October in the years 288, 1436, 1439, 1743, and 1798. These dates render it somewhat probable that the period is about 27½ years. Thus:
A.D.288 to 143942periods of27.405years each.1439 to 174311"27.636" "1743 to 17982"27.500" "
If these periods are correct, it is a remarkable coincidence that the aphelion distances of the meteoric rings of April 20, October 18, November 14, and December 12, as well as those of the comets 1866 I., and 1867 I., are all nearly equal to the mean distance of Uranus.
The Meteors of April 30, May 1.
Professor Schiaparelli, in his list of meteoric showers whose radiant points are derived from observations made in Italy during the years 1868, 1869, and 1870, describes one as occurring on April 30 and May 1; the radiant being in the Northern Crown. The same shower has also been recognized by R. P. Greg, F.R.S., of Manchester, England. This meteor-stream, it is now proposed to show, is probably derived from one much more conspicuous in ancient times.
In Quetelet's "Physique du Globe" we find meteoric displays of the following dates. In each case the corresponding day for 1870 is also given,[28]in order to exhibit the close agreement of the epochs:
1.A.D.401,April9th;corresponding toApril 29th,for 1870.2.538,"6th;"April 25th,"3.839,"17th;"May 1st,"4.927,"17th;"April 30th,"5.934,"18th;"May 1st,"6.1009,"16th;"April 28th,"
The epochs of 927 and 934 suggest as probable the short period of 7 years. It is found accordingly that the entire interval of 608 years—from 401 to 1009—is equal to 89 mean periods of 6.8315 years each. With this approximate value the six dates are all represented as follows:
FromA.D.401 toA.D.538,20periods of6.85years.538 to839,44"6.84"839 to927,13"6.77"927 to934,1"7.00"934 to1009,11"6.82"
This period nearly corresponds to those of several comets whose aphelion distances are somewhat greater than the mean distance of Jupiter. So long as the cluster occupied but a small arc of the orbit the displays would evidently be separated by considerable intervals. The comparative paucity of meteors in modern times may be explained by the fact that the ring has been subject to frequent perturbations by Jupiter.
Groups in which the Meteoroids are sparsely scattered.
By the labors of Heis, Greg, Herschel, Schiaparelli, and others, the radiants of more than fifty sparsely strewn meteor-systems have been determined. Of these the following, which are well defined, seem worthy of special study:
DATE.POSITION OF RADIANT.R. A.N. Decl.January 1-4234°51°January 18232°36°April 25142°53°
The orbits and periods, except in the few cases previously considered, are entirely unknown. Some of the observed clusters are probably thedébrisof ancient comets whose aphelia were in the vicinity of Jupiter's orbit.
The fact that comets and meteors, or at least a large proportion of such bodies, have entered the solar system from stellar space, is now admitted by all astronomers. The question, however, in regard to the origin and nature of these cosmical clouds still remains undecided. The theory that they consist of matter expelled with great velocity from the fixed stars appears to harmonize the greatest number of facts, and is accordingly entitled to respectful consideration. The evidence by which it is sustained may be briefly stated as follows:
1. The observations of Zollner, Respighi, and others, have indicated the operation of stupendous eruptive forces beneath the solar surface. The rose-colored prominences, which Janssen and Lockyer have shown to be masses of incandescent hydrogen, are regarded by Professor Respighi as phenomena of eruption. "They are the seat of movements of which no terrestrial phenomenon can afford any idea; masses of matter, the volume of which is many hundred times greater than that of the earth, completely changing their position and form in the space of a few minutes." The nature of this eruptive force is not understood. We may assume, however, that it was in active operationlong before the sun had contracted to its present dimensions.
2. With an initial velocity of projection equal to 380 miles per second, the matter thrown off from the sun would be carried beyond the limits of the solar system, never to return. With velocities somewhat less, it would be transported to distances corresponding to those of the aphelia of the periodic comets.
3. On the 7th of September, 1871, Professor Young, of Dartmouth College,[29]witnessed an extraordinary explosion on the sun's surface. The observer, with his telescope, followed the expelled matter to an elevation of over 200,000 miles. The mean velocity between the altitudes of 100,000 and 200,000 miles was 166 miles per second. This rate of motionin vacuowould indicate an initial velocity of about 260 miles per second. But the sun is surrounded by an extensive atmosphere, whose resistance must have greatly retarded the velocity of the outrush before reaching the height of 100,000 miles. The original velocity of these hydrogen clouds was therefore sufficient, in all probability, to have carried them, if unresisted, beyond the solar domain. Solid or dense matter propelled with equal force would doubtless have been driven off never to return.[30]
4. This eruptive force, whatever be its nature, is probably common to the sun and the so-called fixedstars. If so, the dispersed fragments of ejected matter ought to be found in the spaces intervening between sidereal systems. Accordingly, the phenomena of comets and meteors have demonstrated the existence of such matter, widely diffused, in the portions of space through which the solar system is moving.
5. According to Mr. Sorby the microscopic structure of the aerolites he has examined points evidently to the fact that they have been at one time in a state of fusion from intense heat,—a fact in striking harmony with this theory of their origin.
6. The velocity with which some meteoric bodies have entered the atmosphere has been greater than that which would have been acquired by simply falling toward the sun from any distance, however great. On the theory of their sidereal origin, this excess of velocity has been dependent on the primitive force of expulsion. The shower of aerolites which fell at Pultusk, Poland, on the 30th of January, 1868,[31]is not only a remarkable illustration of the fact here stated, but also of another which may be accounted for by the same theory, viz.: that meteoric bodies sometimes enter the solar system in groups or clusters.
7. A striking argument in favor of this theory may be derived from the researches of the late Professor Graham, considered in connection with those of Dr. Huggins and other eminent spectroscopists. Professor Graham found large quantities of hydrogen confined in the pores or cavities of certain meteoricmasses. Now, the spectroscope has shown that the sun's rose-colored prominences consist of immense volumes of incandescent hydrogen; that the same element exists in great abundance in many of the fixed stars, and even in certain nebulæ; and that the star in the Northern Crown, whose sudden outburst in 1866 so astonished the scientific world, afforded decided indications of its presence.
[1]Meteoric Astronomy.
[1]Meteoric Astronomy.
[2]Hind.
[2]Hind.
[3]The Chinese, however, as appears from Biot's researches, had observed the same fact 700 years earlier. See Humboldt's Cosmos, vol. iv. (Bohn's ed.), p. 544.
[3]The Chinese, however, as appears from Biot's researches, had observed the same fact 700 years earlier. See Humboldt's Cosmos, vol. iv. (Bohn's ed.), p. 544.
[4]See the Catalogues of Chambers and Williams.
[4]See the Catalogues of Chambers and Williams.
[5]The average number.
[5]The average number.
[6]Monthly Notices of the R. A. S., vol. xxv., p. 243.
[6]Monthly Notices of the R. A. S., vol. xxv., p. 243.
[7]Dr. Lardner.
[7]Dr. Lardner.
[8]The tail of the first comet of 1865 (observed in the Southern Hemisphere) attained the unprecedented length of 150°.—M. N. R. A. S., vol. xxv., p. 220.
[8]The tail of the first comet of 1865 (observed in the Southern Hemisphere) attained the unprecedented length of 150°.—M. N. R. A. S., vol. xxv., p. 220.
[9]This chapter is the substance of a paper read before the American Philosophical Society, November 19, 1869.
[9]This chapter is the substance of a paper read before the American Philosophical Society, November 19, 1869.
[10]Halley's cometin apheliois 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?
[10]Halley's cometin apheliois 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?
[11]Danville Quarterly Review, December, 1861.
[11]Danville Quarterly Review, December, 1861.
[12]Others, it was supposed, might have originated within the system,—a view which the writer has not wholly abandoned.
[12]Others, it was supposed, might have originated within the system,—a view which the writer has not wholly abandoned.
[13]"Quæst. Nat.," lib. vii., cap. xvi.
[13]"Quæst. Nat.," lib. vii., cap. xvi.
[14]Chambers' "Descr. Astr.," p. 374.
[14]Chambers' "Descr. Astr.," p. 374.
[15]Ibid., p. 383.
[15]Ibid., p. 383.
[16]Ibid., p. 388.
[16]Ibid., p. 388.
[17]Hevelius, "Cometographia," p. 341. See also Grant's "Hist. of Phys. Astr.," p. 302.
[17]Hevelius, "Cometographia," p. 341. See also Grant's "Hist. of Phys. Astr.," p. 302.
[18]"Cometographia," p. 417.
[18]"Cometographia," p. 417.
[19]Williams' "Chinese Observations of Comets," p. 73.
[19]Williams' "Chinese Observations of Comets," p. 73.
[20]One of the parts was seen at Madras, India, on the mornings of December 2 and 3, 1872.
[20]One of the parts was seen at Madras, India, on the mornings of December 2 and 3, 1872.
[21]New Concord is close to the Guernsey county line. Nearly all the stones fell in Guernsey.
[21]New Concord is close to the Guernsey county line. Nearly all the stones fell in Guernsey.
[22]The first indication of the approaching shower was the appearance of meteors in unusual numbers at Malta, on the 13th of November, 1864. In 1865, as observed at Greenwich and other stations, they were still more numerous.
[22]The first indication of the approaching shower was the appearance of meteors in unusual numbers at Malta, on the 13th of November, 1864. In 1865, as observed at Greenwich and other stations, they were still more numerous.
[23]See page 30.
[23]See page 30.
[24]Recent in comparison with the origin of the August meteors, which constitute a continuous ring.
[24]Recent in comparison with the origin of the August meteors, which constitute a continuous ring.
[25]Mr. Swift, of Marathon, N. Y., had two or three days priority in the discovery of this comet, but unfortunately delayed his announcement of the fact.
[25]Mr. Swift, of Marathon, N. Y., had two or three days priority in the discovery of this comet, but unfortunately delayed his announcement of the fact.
[26]Astr. Nach., Nos. 1710, 1711. For a fuller statement of Schiaparelli's theory, see Silliman's Journal for May, 1867.
[26]Astr. Nach., Nos. 1710, 1711. For a fuller statement of Schiaparelli's theory, see Silliman's Journal for May, 1867.
[27]The radiant of the Biela meteors is nearGamma Andromedæ.
[27]The radiant of the Biela meteors is nearGamma Andromedæ.
[28]Making proper allowance for the precession of the equinoxes.
[28]Making proper allowance for the precession of the equinoxes.
[29]Boston Journal of Chemistry, November, 1871.
[29]Boston Journal of Chemistry, November, 1871.
[30]See Mr. Proctor's interesting discussion of this subject in the Monthly Notices of the R.A.S., vol. xxxii.
[30]See Mr. Proctor's interesting discussion of this subject in the Monthly Notices of the R.A.S., vol. xxxii.
[31]See Chapter VII.
[31]See Chapter VII.
BY THE AUTHOR OF THIS VOLUME.
METEORIC ASTRONOMY:
A TREATISE ON
SHOOTING STARS, FIRE BALLS,AND AEROLITES.
ByDANIEL KIRKWOOD, LL.D.
12mo. Extra Cloth. $1.50.
⁂ For sale by Booksellers generally, or will be sent by mail, postpaid, on receipt of the price by
J. B. LIPPINCOTT & CO., Publishers,715 and 717 Market St., Philadelphia.