Astronomical Curiosities Part 8

A.D. 1402. A comet appeared in February of this year, which was visible in daylight for eight days. "On Palm Sunday, March 19, its size was prodigious." Another comet, visible in the daytime, was seen from June to September of the same year.

When the orbit of the comet known as 1889 V was computed, it was found that it had pa.s.sed through Jupiter's system in 1886 (July 18-21). The calculations show that it must have pa.s.sed within a distance of 112,300 miles of the planet itself--or less than half the moon's distance from the earth--and "its centre may possibly have grazed the surface of Jupiter."[217]

Sir John Herschel thought that the great comet of 1861 was by far the brightest comet he had ever seen, those of 1811 and 1858 (Donati's) not excepted.[218] Prof. Kreutz found its period of revolution round the sun to be about 409 years, with the plane of the orbit nearly at right angles to the plane of the ecliptic.

On November 9, 1795, Sir William Herschel saw the comet of that year pa.s.s centrally over a small double star of the 11th and 12th magnitudes, and the fainter of the two components remained distinctly visible during the comet's transit over the star. This comet was an appearance of the comet now known as Encke's.[219] Struve saw a star of the 10th magnitude through nearly the brightest part of Encke's comet on November 7, 1828, but the star's light was not dimmed by the comet.

Sir John Herschel saw a cl.u.s.ter of stars of the 16th or 17th magnitude through Biela's comet, although the interposed cometary matter must have been at least 50,000 miles in thickness.[220]

Bessel found that on September 29, 1835, a star of the 10th magnitude shone with undimmed l.u.s.tre through the tail of Halley's comet within 8 seconds of arc of the central point of the head. At Dorpat (Russia) Struve saw the same star "in conjunction only 2"2 from the brightest point of the comet. The star remained continuously visible, and its light was not perceptibly diminished whilst the nucleus of the comet seemed to be almost extinguished before the radiance of the small star of the 9th or 10th magnitude."[221]

Webb says--

"Donati saw a 7 mg. star enlarged so as to show a sensible disc, when the nucleus of comet III., 1860, pa.s.sed very near it. Stars are said to have started, or become tremulous, during occultations by comets.

Birmingham observed the comet of Encke illuminated by a star over which it pa.s.sed, August 23, 1868; and Klein, in 1861, remarked an exceptional twinkling in 5 mg. stars involved in the tail."[222]

The comet of 1729 had the greatest perihelion distance of any known comet;[223] that is, when nearest to the sun, it did not approach the central luminary within four times the earth's distance from the sun!

Barnard's comet, 1889 I., although it never became visible to the naked eye, was visible with a telescope from September 2, 1888, to August 18, 1890, or 715 days--the longest period of visibility of any comet on record. When last seen it was 6 times the earth's distance from the sun, or about 580 millions of miles,[224] or beyond the orbit of Jupiter!

Messier, who was called "the comet ferret," discovered "all his comets with a small 2-foot telescope of 2 inches aperture, magnifying 5 times, and with a field of 4."[225]

It is a very curious fact that Sir William Herschel, "during all his star-gaugings and sweeps for nebulae, never discovered a comet;"[226] that is an object which was afterwards _proved_ to be a comet. Possibly, however, some of his nebulae which are now missing, may have been really comets.

Sir William Herschel found the diameter of the head of the great comet of 1811 to be 127,000 miles. The surrounding envelope he estimated to be at least 643,000 miles, or about three-fourths of the sun's diameter.

On a drawing of the tails of the great comet of 1744 given in a little book printed in Berlin in that year, no less than 12 tails are shown!

These vary in length and brightness. A copy of this drawing is given in _Copernicus_.[227] The observations were made by "einen geschichten Frauenzimmer," who Dr. Dreyer identifies with Christian Kirch, or one of her two sisters, daughters of the famous Gottfried and Maria Margaretta Kirch (_Idem_, p. 107). Dr. Dreyer thinks that the drawing "seems to have been carefully made, and not to be a mere rough sketch as I had at first supposed" (_Idem_, p. 185).

The tails of some comets were of immense length. That of the comet of 1769 had an absolute length of 38 millions of miles. That of 1680, 96 million of miles, or more than the sun's distance from the earth. According to Sir William Herschel, the tail of the great comet of 1811 was over 100 millions of miles in length. That of the great comet of 1843--one of the finest in history--is supposed to have reached a length of 150 millions of miles![228]

In width the tails of comets were in some cases enormous. According to Sir William Herschel, the tail of the comet of 1811 had a diameter of 15 millions of miles! Its volume was, therefore, far greater than that of the sun![228]

According to Hevelius the comet of 1652 was of such a magnitude that it "resembled the moon when half full; only it shone with a pale and dismal light."[229]

Halley's comet at its next appearance will be examined with the spectroscope for the first time in its history. At its last return in 1835, the spectroscope had not been invented.

For the great comet of 1811, Arago computed a period of 3065 years; and Encke found a period of 8800 years for the great comet of 1680.[230]

The variation in the orbital velocity of some comets is enormous. The velocity of the comet of 1680 when pa.s.sing round the sun (perihelion) was about 212 miles a second! Whereas at its greatest distance from the sun (aphelion) the velocity is reduced to about 10 feet a second!

CHAPTER XII

Meteors

Mr. Denning thinks that the meteor shower of the month of May, known as the Aquarids, is probably connected with Halley's comet. The meteors should be looked for after 1 a.m. during the first week in May, and may possibly show an enhanced display in May, 1910, when Halley's comet will be near the sun and earth.[231]

On November 29, 1905, Sir David Gill observed a fireball with an apparent diameter equal to that of the moon, which remained visible for 5 minutes and disappeared in a hazy sky. Observed from another place, Mr. Fuller found that the meteor was visible 2 hours later! Sir David Gill stated that he does not know of any similar phenomenon.[232]

Mr. Denning finds that swiftly moving meteors become visible at a greater height above the earth's surface than the slower ones. Thus, for the Leonids and Perseids, which are both swift, it has been found that the Leonids appear at an average height of 84 miles, and disappear at a height of 56 miles; and the Perseids at 80 and 54 miles respectively. "On the other hand, the mean height of the very slow meteors average about 65 miles at the beginning and 38 miles at the end of their appearance."[233]

During the night of July 21-22, 1896, Mr. William Brooks, the well-known astronomer, and director of the Smith Observatory at Geneva (New York), saw a round dark body pa.s.s slowly across the moon's bright disc, the moon being nearly full at the time. The apparent diameter of the object was about one minute of arc, and the duration of the transit 3 or 4 seconds, the direction of motion being from east to west. On August 22 of the same year, Mr. Gathman (an American observer) saw a meteor crossing the _sun's_ disc, the transit lasting about 8 seconds.[234]

A meteor which appeared in Italy on July 7, 1892, was shown by Prof. von Niessl to have had an _ascending_ path towards the latter end of its course! The length of its path was computed to be 683 miles. When first seen, its height above the earth was about 42 miles, and when it disappeared its height had increased to about 98 miles, showing that its motion was directed upwards![235]

In the case of the fall of meteoric stones, which occasionally occur, it has sometimes been noticed that the sound caused by the explosion of the meteorite, or its pa.s.sage through the air, is heard before the meteorite is seen to fall. This has been explained by the fact that owing to the resistance of the air to a body moving at first with a high velocity its speed is so reduced that it strikes the earth with a velocity less than that of sound. Hence the sound reaches the earth before the body strikes the ground.[236]

The largest meteoric stone preserved in a museum is that known as the Anighita, which weighs 36 tons, and was found at Cape York in Greenland. It was brought to the American Museum of Natural History by Commander R. E. Peary, the Arctic explorer.

The second largest known is that of Bacubirito in Mexico, the weight of which is estimated at 27 tons.

The third largest is that known as the Williamette, which was found in 1902 near the town of that name in Western Oregon (U.S.A.). It is composed of metallic nickel-iron, and weighs about 13 tons. It is now in the American Museum of Natural History.

A large meteorite was actually seen, from the deck of the steamer _African Prince_, to fall into the Atlantic Ocean, on October 7, 1906! The captain of the vessel, Captain Anderson, describes it as having a train of light resembling "an immense broad electric-coloured band, gradually turning to orange, and then to the colour of molten metal. When the meteor came into the denser atmosphere close to the earth, it appeared, as nearly as is possible to describe it, like a molten ma.s.s of metal being poured out. It entered the water with a hissing noise close to the ship."[237] This was a very curious and perhaps unique phenomenon, and it would seem that the vessel had a narrow escape from destruction.

In Central Arizona (U.S.A.) there is a hill called c.o.o.n b.u.t.te, or c.o.o.n Mountain. This so-called "mountain" rises to a height of only 130 to 160 feet above the surrounding plain, and has on its top a crater of 530 to 560 feet deep; the bottom of the crater--which is dry--being thus 400 feet below the level of the surrounding country. This so-called "crater" is almost circular and nearly three-quarters of a mile in diameter. It has been suggested that this "crater" was formed by the fall of an enormous iron meteorite, or small asteroid. The "crater" has been carefully examined by a geologist and a physicist. From the evidence and facts found, the geologist (Mr. Barringer) states that "they do not leave, in my mind, a scintilla of doubt that this mountain and its crater were produced by the impact of a huge meteorite or small asteroid." The physicist (Mr.

Tilghmann) says that he "is justified, under due reserve as to subsequently developed facts, in announcing that the formation at this locality is due to the impact of a meteor of enormous and unprecedented size." There are numerous ma.s.ses of meteoric iron in the vicinity of the "crater." The so-called Canyon Diabolo meteorite was found in a canyon of that name about 2 miles from the c.o.o.n Mountain. The investigators estimate that the great meteoric fall took place "not more than 5000 years ago, perhaps much less." Cedar trees about 700 years old are now growing on the rim of the mountain. From the results of artillery experiments, Mr.

Gilbert finds that "a spherical projectile striking solid limestone with a velocity of 1800 feet a second will penetrate to a depth of something less than two diameters," and from this Mr. L. Fletcher concludes "that a meteorite of large size would not be prevented by the earth's atmosphere from having a penetration effect sufficient for the production of such a crater."[238]

The meteoric origin of this remarkable "crater" is strongly favoured by Mr. G. P. Merrill, Head Curator of Geology, U.S. National Museum.

The Canyon Diabolo meteorite above referred to was found to contain diamonds! some black, others transparent. So some have said that "the diamond is a gift from Heaven," conveyed to earth in meteoric showers.[239] But diamond-bearing meteorites would seem to be rather a freak of nature. It does not follow that _all_ diamonds had their origin in meteoric stones. The mineral known as periodot is frequently found in meteoric stones, but it is also a const.i.tuent of terrestrial rocks.

In the year 1882 it was stated by Dr. Halm and Dr. Weinhand that they had found fossil sponges, corals, and crinoids in meteoric stones! Dr.

Weinhand thought he had actually determined three genera![240] But this startling result was flatly contradicted by Carl Vogt, who stated that the supposed fossils are merely crystalline conformations.[241]

Some meteorites contain a large quant.i.ty of occluded gases, hydrogen, helium, and carbon oxides. It is stated that Dr. Odling once "lighted up the theatre of the Royal Inst.i.tution with gas brought down from interstellar s.p.a.ce by meteorites"![242]

On February 10, 1896, a large meteorite burst over Madrid with a loud report. The concussion was so great that many windows in the city were broken, and some part.i.tions in houses were shaken down![243]

A very brilliant meteor or fireball was seen in daylight on June 9, 1900, at 2{h} 55{m} p.m. from various places in Surrey, Suss.e.x, and near London.

Calculations showed that "the meteor began 59 miles in height over a point 10 miles east of Valognes, near Cherbourg, France. Meteor ended 23 miles in height, over Calais, France. Length of path 175 miles. Radiant point, 280, 12."[244]

It was decided some years ago "in the American Supreme Court that a meteorite, though a stone fallen from heaven, belongs to the owner of the freehold interest in the land on which it falls, and not to the tenant."[245]

With reference to the fall of meteoric matter on the earth, Mr. Proctor says, "It is calculated by Dr. Kleiber of St. Petersburgh that 4250 lbs.

of meteoric dust fall on the earth every hour--that is, 59 tons a day, and more than 11,435 tons a year. I believe this to be considerably short of the truth. It sounds like a large annual growth, and the downfall of such an enormous ma.s.s of meteoric matter seems suggestive of some degree of danger. But in reality, Dr. Kleiber's estimate gives only about 25 millions of pounds annually, which is less than 2 ounces annually to each square mile of the earth's surface,"[246] a quant.i.ty which is, of course, quite insignificant.

According to Humboldt, Chladni states that a Franciscan monk was killed by the fall of an aerolite at Milan in the year 1660.[247] Humboldt also mentions the death by meteoric stones of a monk at Crema on September 4, 1511, and two Swedish sailors on board ship in 1674.[248]

It is a curious fact that, according to Olbers, "no fossil meteoric stones" have ever been discovered.[249] Considering the number which are supposed to have fallen to the earth in the course of ages, this fact seems a remarkable one.