Popular Science Monthly/Volume 54/February 1899/The Great Bombardment
|THE GREAT BOMBARDMENT.|
A THIN stratum of air, an invisible armor of great tenuity, lies between man and the menace of possible annihilation.
The regions of space beyond our planet are filled with flying fragments. Some meet the earth in its onward rush; others, having attained inconceivable velocity, overtake and crash into the whirling sphere with loud detonation and ominous glare, finding destruction in its molecular armor, or perhaps ricocheting from it again into the unknown. Some come singly, vagrant fragments from the infinity of space; others fall in showers like golden rain; all constituting a bombardment appalling in its magnitude. It has been estimated that every twenty-four hours the earth or its atmosphere is struck by four hundred million missiles of iron or stone, ranging from an ounce up to tons in weight. Every month there rushes upon the flying globe at least twelve billion iron and stone fragments, which, with lurid accompaniment, crash into the circumambient atmosphere. Owing to the resistance offered by the air, few of these solid shots strike the earth. They move out of space with a possible velocity of thirty or forty miles per second, and, like moths, plunge into the revolving globe, lured to their destruction by its fatal attraction. The moment they enter our atmosphere they ignite; the air is piled up and compressed ahead of them with inconceivable force, the resultant friction producing an immediate rise in temperature, and the shooting star, the meteor of popular parlance, is the result.
A simple experiment, made by Joule and Thomson, well illustrates the possibility of this rise in temperature by atmospheric friction. If a wire is whirled through the air at a rate of one hundred and seventy-five feet per second, a rise of one degree, centigrade, will be noticed. If the revolutions are increased to three hundred and seventy-two feet per second, the elevation will be 5.3° C. If the temperature increases as the square of the velocity, a rate of speed
of twenty miles per second would develop a temperature not far from 360,000° C, which is probably far less than that at the surface of the ordinary meteor as it is seen blazing through our atmosphere. If the meteor is small it is often consumed by the intense heat generated; but larger fragments, owing to their velocity and
the fact that they are poor conductors of heat and burn slowly, reach the surface and bury themselves in the sea or earth. But few escape the inevitable consequences of the contact, and of the untold millions which have struck the earth within the memory of man but five hundred and thirty have been seen to fall. The phenomena associated with the plunging meteor is most interesting. A blaze of light, as the terrific beat ignites the iron, announces its entrance into our atmosphere. It may be red, yellow, white, green, or blue, all these hues having been observed. Then follows the explosion, caused by the contact with the air piled up ahead, and in certain instances a loud detonation or a series of noises is heard, which may be repeated indefinitely until the meteoric mass is completely destroyed, and drops, a shower of disintegrated particles, which fall rattling to the ground.
The blaze of light does not continue to the earth, nor does the meteor, should it survive, strike the ground with the velocity with which it entered the atmosphere, as the latter often arrests its motion so completely that it drops upon the earth by its own weight, well illustrated by the meteorites of the Hesslefall, which dropped upon ice but a few inches thick, rebounding as they fell. Thus the atmosphere protects the inhabitants of the globe from a terrific bombardment by destroying many of the largest meteorites, reducing the size of others before they reach the surface and arresting the velocity so that few bury themselves deeply in the soil.
The writer observed a remarkable meteor in 1894. It entered our atmosphere, apparently, over the Mojave Desert, in California, and exploded over the San Gabriel Valley, though without any appreciable sound, and after the first flash disappeared, leaving in the air a large balloon-shaped object of yellow light which lasted some moments, presenting a remarkable spectacle. In this instance the meteor had probably exploded or been consumed, leaving only the light to tell the story, the atmospheric armor of the earth having successfully warded off the blow.
Viewing the facts as they exist, the earth, a seeming fugitive mass flying through space, vainly endeavoring to break the bonds which bind it to the sun, hunted, bombarded with strange missiles hurled from unseen hands or forces from the infinity of space, it is little wonder that the ancients and some savage races of later times invested the phenomena with strange meanings. It requires but little imagination to see in the flying earth a living monster followed by shadowy furies which hurl themselves upon it, now vainly attempting to reach the air-protected body or again striking it with terrific force, lodging deep in its sides amid loud reverberation and dazzling blaze of light.
Meteorites have been known from the very earliest times, and have often been regarded as miraculous creatures to be worshiped and handed down from family to family. The famous meteorite which fell in Phrygia, centuries ago, was worshiped as Cybele, "the mother of the gods," and about the year 204 b. c. was carried to Rome with much display and ceremony, when people of all classes fell down before it, deeming it a messenger from the gods. Diana of Ephesus and the famous Cyprian Venus were, in all probability, meteoric stones which were seen to fall, and were worshiped for the same reason as above. Livy describes a shower of meteorites which fell about the Alban Mount 652 b. c. The senate was demoralized, and certain prophets announced it a warning from heaven, so impressing the lawmakers that they declared a nine-days' festival with which to propitiate the gods. The visitor to Mecca will find enshrined in a place of honor a meteorite which can be traced back beyond 600 a. d., and which is worshiped by pilgrims. The Tartars pointed out a meteorite to Pallas, in 1772, which had fallen at Krasnojarsk, and which they considered a holy messenger from heaven. A large body of meteoric iron found in Wichita County, Texas, was regarded by the Indians as a fetich. They told strangers that it came from the sky as a messenger from the Great Spirit. This meteorite was stationed at a point where two Indian trails met, and was observed and worshiped as a shrine.
The Chinese have records of meteors which fell 644 b. c. The oldest authentic fall in which the stone is preserved is that of Ensisheim, Elsass, Germany, in 1492. The stone, which weighed two hundred and sixty pounds, fell with a loud roar, much to the dismay of the peasantry, penetrating the ground to a depth of five feet. It was secured by King Maximilian, who, after presenting the Duke Sigismund with a section, hung the remainder in the parish church as a holy relic, where, it is said, it may still be seen.
Meteorites vary in size from minute objects not larger than a pea to masses of iron of enormous size. The Chupaderos meteorite, which fell in Chihuahua, Mexico, weighs twenty-five tons. Another, which fell in Kansas, broke into myriads of pieces, the sections found weighing thirteen hundred pounds. A meteorite in the Vienna Museum, which fell in Hungary, weighs six hundred and forty-seven pounds, while the Cranbourne meteorite in the British Museum weighs four tons. The Red River meteorite in the Yale Museum weighs sixteen hundred and thirty pounds. The largest meteorite known was discovered within the Arctic Circle by Lieutenant Peary. The Eskimos had known of it for generations as a source of supply for iron. It was found by Lieutenant Peary in May, 1894, but, owing to its enormous weight, could not be removed until the summer of 1897, when, after much labor, it was excavated and hoisted into the hold of the steam whaling bark Hope and carried to New York, where it has found a resting place in the cabinet of the American Museum of Natural History. It is believed to weigh one hundred tons.
Up to 1772 the stories of bodies falling from space were not entertained seriously by scientific men. So eminent a scientist as Lavoisier, after thoroughly investigating a case, decided that it was merely a stone which had been struck by lightning. Falls finally occurred which demonstrated beyond dispute that the missiles came from space, and science recognized the fact that the earth was literally being bombarded, and that human safety was due to the atmospheric armor, scarcely one hundred miles thick, that enveloped the earth. Instances of the destruction of human life from this cause are very rare. Some years ago a meteorite crushed into the home of an Italian peasant, killing the occupant; and cattle have been known to be destroyed by them; but such instances are exceptional. In 1660 a meteorite fell at Milan, on the authority of the Italian physicist Paolo Maria Tezzayo, killing a Franciscan monk. Humboldt is authority for the statement that a monk was struck dead by a meteorite at Crema, September 4, 1511; and in 1674, on the same authority, a meteorite struck a ship at sea and killed two Swedish sailors.
In December, 1795, at Wold Cottage, in Yorkshire, England, a stone weighing fifty pounds dashed through the air with a loud roar, alarming people in the vicinity, and burying itself in the ground not thirty feet from a laborer. This mass, though undoubtedly traveling, when it struck our atmosphere, at a rate of at least thirty miles a second, was checked so completely that it sank but twelve inches into the soft chalk. Great as is the heat generated during the passage of a meteorite through the air, it does not always permeate the entire body. This was well illustrated in the case of the meteorite which fell at Dhurmsala, Kangra, Punjaub, India, in 1860, fragments of which can be seen in the Field Museum in Chicago. Of it Dr. Oliver C. Farington says: "The fragments were so cold as to benumb the fingers of those who collected them. This is perhaps the only instance known in which the cold of space has become perceptible to human senses."
Some of the individual falls during recent years have attracted widespread attention. One of the most remarkable is known as the Great Kansas Meteor. It was evidently of large size, flashing into sight eighty or ninety miles from the earth, on the 20th of June, 1876, over the State of Kansas. To the first observers it appeared to come from the vicinity of the moon, and resembled a small moon or a gigantic fire ball, blazing brightly, and creating terror and amazement among thousands of spectators who witnessed its flight. It passed to the east, disappearing near the horizon in a blaze of light. The entire passage occupied nearly fifty seconds, being visible to the inhabitants of Iowa, Nebraska, Missouri, Indiana, Wisconsin, Illinois, Michigan, Kentucky, Ohio, Pennsylvania, and West Virginia.
This visitor created the greatest alarm and apprehension along its path, the blaze of light being accompanied by repeated explosions and detonations which sounded like the rumble and roar of cannonading. To some it appeared like the rattling of heavy teams over a rough, rocky road; others believed subterranean explosions accompanied the fall. Horses ran away, stock hurried bellowing to cover, and men, women, and children crouched in fear or fled before the fiery visitor whose roar was distinctly heard several minutes after it had disappeared. As the meteor crossed the Mississippi River the noise of the explosions increased in severity, and were distinctly heard sixty or seventy miles from its path, or a distance of one hundred and forty miles apart. The great ball of flame remained intact as it crossed five or six States, but as it passed over central Illinois loud detonations were heard and the light spread out like an exploding rocket with flashing points. This was the death and destruction of the monster, and from here it dashed on, a stream or shower of countless meteors instead of a solid body, forming over Indiana and Ohio a cluster over forty miles long and five in breadth, showing that while
the meteor had broken up it was still moving with great velocity. How far it traveled is not known, as it was not seen to strike. Observers in Pennsylvania saw it rushing in the direction of New York, and people in that State, where the day was cloudy, heard strange rumblings and detonations. Houses rattled, and the inhabitants along the line the meteor was supposed to have passed accredited the phenomena to an earthquake. Somewhere, perhaps in the forest region of the Adirondacks, or in the Atlantic, lies the wreck of this meteor. But one fragment was 'found. A farmer in Indiana, while watching its passage heard the thud of a falling object, and going to the spot the following morning found a small meteorite weighing two thirds of a pound.
This marvelous body was first observed in all probability in the northwestern corner of the Indian Territory, possibly sixty or seventy miles above the earth, and from here it dashed along with repeated explosions, almost parallel to the earth's surface, disappearing over New York.
Another remarkable meteor fell into the Atlantic Ocean far out at sea, July 20, 1860. It resembled the one mentioned above in that it was accompanied by a marvelous pyrotechnic display. It first appeared in the vicinity of Michigan, blazing out with a fiery glow that filled the heavens with light. Cocks crowed, oxen lowed, and people
rushed from their homes along its course over the States of New York, Pennsylvania, and New Jersey. When last seen, over the Atlantic, it had separated into three parts, which followed each other as separate fire bodies, without the noise which was the accompanying feature of the Kansas meteor.
Doubtless the majority of meteors plunge into the ocean, and in modern times several large meteoric bodies have narrowly escaped passing vessels. On December 1, 1896, the officers of the ship Walkomming, bound from New York to Bremen, noticed a large and brilliant meteor flashing down upon them. Its direction was from southeast to northwest, and it plunged into the sea ahead of the vessel with a loud roar and hissing sound; a few minutes later an immense tidal wave, presumably caused by the fall, struck the ship, doing no little damage. Even more remarkable was the escape of the British ship Cawdor, which was given up by the underwriters, but which reached San Francisco November 20, 1897. During a heavy
storm, August 20th, a large meteor flashed from the sky and passed between the main and mizzen masts, crashing into the sea with a blinding flash and deafening detonation. For a moment it was thought the ship was on fire, and the air was filled with sulphurous fumes.
In 1888 a meteor dashed into the atmosphere of the earth and made a brilliant display over southern California. It appeared between twelve and one o'clock in the morning, and shot across the heavens, a fiery red mass—not like the ordinary meteor, but writhing and twisting in a manner peculiarly its own, resembling a huge serpent. When it had passed nearly across the sky it apparently stopped and doubled in the form of a horseshoe, according to the informant of the writer, as large as a half-mile race track. The horseshoe remained visible several minutes, gradually disappearing. The brilliancy of this meteor can be imagined when it is known that the entire San Gabriel Valley was illumined as though an electric light of great power had suddenly been flashed upon it.
Some time in past ages a meteorite weighing at least ten tons shot into our atmosphere and struck the earth near the famous Cañon Diablo in Arizona, the mysterious gulch crossed by the Atchison, Topeka and Santa Fé Railroad. The discovery was made several
years ago by a sheep herder, named Armijo. Finding a piece of iron with a peculiar lustrous surface which he believed to be silver, he carried it to one of the towns, where it finally fell into the hands of a geologist, who pronounced it a meteorite. The discovery was followed up, and on the crest and in the vicinity of a singular cone about four thousand feet in diameter pieces of a meteorite were found on the surface, which gave a combined weight of ten tons, in all probability but a fraction of the real monster. The iron masses were widely scattered over the slope and the adjacent mesa, and it was assumed that a gigantic meteorite or star had fallen and produced the cone, another striking the earth and forming what is now known as the Cañon Diablo. A large piece of meteoric iron was found twenty miles from the cone; another eight miles east of it; two thousand pieces weighing not over a few pounds or ounces were taken from the slopes; two exceeding a thousand pounds were found within a half mile, while forty or fifty weighing about one hundred pounds were discovered within a radius of half a mile. Here not only a meteor, but a large-sized meteoric shower, had succeeded in penetrating the armor of the earth, leaving many evidences of the extraordinary occurrence which may have been witnessed by the early man of what is now known as Arizona. From the peculiar and interesting evidence a geologist deduced the hypothesis that the crater known as Coon Butte could have been produced by a meteor with a diameter of fifteen hundred feet, and a careful examination with a view of discovering it was made with nicely adjusted magnetic
|One Hundred and Sixty-one Pound Meteorite. A part of the ten-ton meteorite which fell at Coon Butte, near Cañon Diablo.||One Hundred and Sixty-one and a Half Pound Meteorite found near Crater of Coon Butte.|
instruments; but in no instance did they indicate the presence of a vast body of metal buried in the earth, and it was assumed that the striking of the crater by the colossal meteorite was a chance blow.
The meteorites or foreign bodies which bombard the earth may be included in three classes—meteoric irons or aërosiderites, meteoric iron stones or aërosiderolites, and meteoric stones, aërolites—all containing elements, about twenty-five in number, which have been found upon the earth. The most conspicuous and important are silicon, iron, nickel, magnesium, sulphur, carbon, and phosphorus, while the others are aluminum, antimony, arsenic, calcium, chlorine, chromium, cobalt, copper, hydrogen, lithium, manganese, oxygen, potassium, Crosses show Large Pieces of the Meteorites found at Coon Butte. (Seven miles in diameter.) sodium, tin, and titanium. Hydrogen and the diamond have also been observed. A number of interesting chemical compounds are found in meteorites not known on the earth, and a study of their character shows that the conditions under which the meteors were formed were entirely different from those which saw the beginning of things terrestrial. In brief, where meteors were born there was an absence of air and water. On the other hand, there was at some stage in the history of meteorites an abundance of hydrogen. The meteoric irons are made up principally of iron with an alloy of nickel, and show a rich crystalline structure, the various angles producing a variety of forms known as Widmanstatten figures which a few years ago formed the basis of a singular sensation. The figures were supposed to be fossil shells and various animals of a diminutive size which once populated the wrecked world of which the meteor was assumed to be a part. These meteoric animals from space were named and classified by several observers, who were finally forced to acknowledge that their creations were the fanciful markings of crystallization.
Another class of meteorites (meteoric iron stones) may be described as spongy masses of nickeliferous iron in whose pores are found grains of chryosite and other silicates. A type of these bodies is the meteor of Pallas, which was discovered by him in 1772. The third class of meteoric stones are those in which the stony or silicous predominates. As a rule they contain scattered metallic grains, but certain ones, as the aërolite which fell at Gara, France, in 1806, contain metallic constituents.
The aërolites present an attractive appearance when made into sections, showing crystals and splinterlike fragments, and under the glass seem to be made up of many minute spheres ranging from those the size of a cherry down to others invisible to the naked eye. The minerals prominent in their composition are chrysolite, bronzite, augite, enstatite, feldspar, chronite, etc., showing a marked similarity to the eruptive rocks so well known on the earth. The collections of famous meteorites in the various museums of the world have constantly been examined and studied with a view to determine their origin, the question being a fascinating one to layman and scientist. Astronomers in the past have variously answered the question. The flying fragments were believed by some to be the wreckage of other worlds. Planets had perhaps collided and been rent asunder in former ages, and space filled with the flying fragments. Others thought that meteors were molten matter thrown from the earth or moon. All these theories have been relinquished in view of evidence of a more or less convincing character pointing to the conclusion that the bombardment of the earth is one of the results of the disintegration of comets. In other words, cometary matter flying not always blindly through space, but in the orbit of the comet of which it originally formed a part, constituting the missiles.
It is known that the meteors were formed in a region where air and water were absent. It is equally evident that life was not a factor in the past history of the bodies, though it must be acknowledged that the hydrocarbons resembling terrestrial bitumens which are found in some meteorites suggest the possibility of vegetable life. These comets, the mysterious bodies which seem to be roving through space, misconceived planets, as it were, forced into the world half made up, offer the best known solution, as they are literally worlds without air or water, enveloped in a strange and ever-changing substitute for atmosphere; ghostly worlds, which seem to be drawn to the sun, then thrown out into space again to repeat the act until the mighty change from close contact with the fiery mass to the intense cold of distant realms wrecks them, scatters their fragments through the infinity of space where they form gigantic rings or clusters of meteoric matter, raining down upon the sun and planets and all heavenly bodies which meet them, adding fuel to the former, material substance to the latter, and in the case of the moon pitilessly bombarding her crust—illustrating the effect of the bombardment of the earth were it deprived of its atmospheric armor.
The evidence which enabled astronomers to definitely associate comets with meteoric showers and falling stars leads one into a world of romance. Schiaparelli, the distinguished Italian astronomer, made the discovery that meteors had a cometic origin. He had been calculating the orbit and motion of the meteorites which produce the August showers, when it occurred to him that they corresponded with those of a certain comet. By following up this clew it was discovered that the orbit of Tempel's comet corresponded with that of the meteors of the November star shower. The most remarkable evidence was that produced by Biela's comet, discovered in 1826. It had a revolution about the sun of six years and eight months. It was seen in 1772, 1805, 1832, 1845, and 1852. The vast mass, which appeared to be rushing around the sun with remarkable velocity, became separated in 1846, dividing into two parts, one hundred and fifty thousand or two hundred thousand miles from each other. In six years the separation had increased to about one and a half million miles. What mighty cataclysm in infinite space caused this rupture the mind of man can not conceive, but something occurred which rent the aerial giant asunder, and so far as known completed its wreck, as from that time Biela's comet has not been seen. In 1872 the comet was looked for, and astronomers predicted that if it did not appear a shower of stars or meteors would be visible—the remains of the lost traveler through space—and that they would diverge from a point in Andromeda.
This remarkable prediction was verified in every particular. When the moment for the appearance of the comet arrived, November 27, 1872, there burst upon the heavens, not Biela's comet, but a marvelous shower of shooting stars, which dashed down from the constellation of Andromeda as predicted. In 1885 this was duplicated, and the atmosphere was apparently filled with shooting stars. Biela's comet had met disaster in infinite space, and the earth was being bombarded with the wreckage.
It is difficult to comprehend the vastness of these clusters of meteors which constitute the wreck of comets and the source of the principal bombardments. Thus the August stream, which gives us the brilliant displays of summer nights, is supposed to be ten million miles in thickness, as the earth dashing through at a rate of two
million miles a day is several days in passing it. We cross the November stream of meteors in a few hours, suggesting a width of forty thousand or fifty thousand miles. This stream of metallic bodies is hundreds of millions of miles in length, and contains myriads of projectiles which may yet be hurled upon the earth or some of the planets of the solar system.
But one piece of Biela's comet, so far as known, was found—a fragment weighing eight pounds falling at Mazapil, Mexico, where it remains one of the most inspiring and interesting of inanimate objects. For years the vast metallic mass, of which this piece formed a part, rushed through space, covering millions of miles; now near the burning surface of the sun, now in regions of space where its heat was scarcely perceptible. For over a century this monster was observed by the inhabitants of the earth, and finally a portion fell and human beings handled and examined it.
The fiery messengers which dash down singly upon the earth, the showers of meteoric stones which flash through our atmosphere with ephemeral gleams, are, then, the remains of gigantic comets which have been seen rushing with apparent erratic course through space, and which by unknown causes have been destroyed and now as meteoric clusters, one of which is estimated to be one billion miles in length and one hundred thousand miles in thickness, and to contain one hundred thousand million meteors, are swinging through space, with many erratic and wandering forms, pouring upon the earth and all the planets of the solar system a mighty and continuous bombardment.
Note.—The meteors shown in the two ideal pictures are, of course, entirely disproportionate in size to the earth and stars. If seen by an observer above the earth, we might imagine an envelope of light around the globe from the continuous ignition of the 150,000,000,000 or more meteors which it is estimated strike the earth every year; in which case, the striking meteors would be represented in the illustrations as a thin light line surrounding the atmospheric envelope of the earth.