Cosmic Debris: Meteorites in History

COSMIC DEBRIS

COSMIC

DEBRIS

Meteorites in History

JOHN G. BURKE

UNIVERSITY OF CALIFORNIA PRESS

Berkeley / Los Angeles / London

University of California Press

Berkeley and Los Angeles, California

University of California Press, Ltd.

London, England

Copyright © 1986 by The Regents of the University of California

Library of Congress Cataloging in Publication Data

Burke, John G.

Cosmic debris.

Bibliography: p.

Includes index.

1. Meteorites—History. I. Title.

QB755.B87 1986 523.5'1 85-28841

ISBN 0-520-05651-5 (alk. paper)

Printed in the United States of America 123456789

To the memory of

PEGGY PORTER BURKE

Contents

Contents

Introduction

1 Disbelief

THE LEGACY OF ARISTOTLE’S METEOROLOGICA

THE GENESIS OF MINERALS AND THUNDERSTONES

DILEMMAS ABOUT FIREBALLS AND GENUINE METEORITES

METEORITE FALLS AND SCIENTIFIC ATTITUDES

Acceptance

FROM DISBELIEF TO ACCEPTANCE

EARLY NINETEENTH-CENTURY THEORIES OF METEORITE ORIGIN

Mathematical Astronomy and Statistics

THE 1833 LEONIDS AND AFTERMATH

A DIGRESSION ON THE FALL OF PECULIAR MATTER

COMETS AND METEOR STREAMS

METEORITE FALLS AND FINDS: THE START OF STATISTICAL ANALYSIS

THE PHENOMENA OF FALL

Nineteenth-Century Foundations of Meteorite Analysis

METHODS

CONSTITUENTS: OLIVINE, PLAGIOCLASE, PYROXENE

CONSTITUENTS: NICKEL-IRON, TROILITE, SCHREIBERSITE

CLASSIFICATIONS

Late Nineteenth-Gentuiy Meteorite Theories

THE THEORIES OF REICHENBACH AND HAIDINGER

PLANETARY OR ASTEROIDAL ORIGIN

ORIGINS FROM THE SUN, NEBULAE, OR COMETS

LIFE IN METEORITES AND ON OTHER PLANETS

6 Curators and Collectors

THE VIENNA AND BRITISH MUSEUM COLLECTIONS TO ABOUT 1860

THE MAJOR EUROPEAN COLLECTIONS IN THE LATE NINETEENTH CENTURY

MAJOR U.S. COLLECTIONS IN THE LATE NINETEENTH AND EARLY TWENTIETH CENTURIES

PRICES AND EXCHANGE VALUES

7 Folklore, Myth, and Utility

BELIEFS ABOUT METEORS

MYTHS AND FOLK BELIEFS ABOUT METEORITES AND THUNDERSTONES

USES OF METEORITES

New Directions 1900-1950

NEW INSIGHTS INTO OLD PROBLEMS

THE SCIENTIFIC USE OF METEORITES

NEW PROBLEMS

9 Contemporary Meteorite Research and Theories

CLASSIFICATION AND AGES

THE ORIGINS OF METEORITES

MATTERS OF LIFE AND DEATH

Notes

References

INDEXES

Name Index

Subject Index

Meteorite Index

Introduction

Tens of millions of meteoroids, solid bodies from outer space, enter the Earth’s atmosphere each year. They are pieces of stone, iron, or stony iron conglomerates, and they range in mass from fractions of a gram to hundreds of kilograms. The smallest are incinerated immediately, emitting little if any visible light. Somewhat larger pieces appear as meteors or shooting stars, brief luminous streaks in the night sky, which result from their incandescence. Meteorites are meteoroids that survive passage through the atmosphere and fall to earth. These larger chunks of matter signal their arrival by appearing as huge fiery masses or fireballs, which light up a broad area of the sky at night and sometimes in daylight. Their extremely rapid transit through the atmosphere creates sonic booms that people far distant from the scene can hear. Fireballs that detonate are called bolides. Sometimes the explosion causes complete disintegration of the meteoroid, so that only dust particles remain to drift slowly to earth. In other instances, the explosion yields a few fragments or a shower of several thousand pieces, which become meteorites. Very rarely, a huge mass weighing thousands of tons penetrates the Earth’s atmosphere, and upon impact with the ground vaporizes almost completely, producing a massive crater, such as Barringer Meteorite Crater in Arizona.

Meteorites have undoubtedly been falling to earth for eons. Scientists make a distinction between meteorite falls and finds. A fall is a meteorite, which observers actually witnessed and the fragments of which were recovered very soon after the event. A find is a meteorite whose fall was not seen, but which was later recognized as a meteorite because of its chemical composition, its mineral constituents, or its structure. A large number of the meteorite finds are irons or stony irons, both because they have a greater resistance to weathering and because their presence has seemed unusual to farmers, hunters, or primitive peoples who have encountered them. It requires keen observation, however, to discriminate between a terrestrial rock and a meteoritic stone, which, particularly if it is friable, disintegrates over time.

Each meteorite has a name—usually that of the town, village, or geographical landmark closest to where it fell or was found. Since the distribution of meteorites is worldwide, a list of their names recalls the index of an atlas: Pultusk (Poland), Sikhote-Alin (USSR), Ogi (Japan), Queen’s Mercy (South Africa), or Dingo Pup Donga (Australia). Before there was universal agreement on nomenclature, some meteorites had several names, which caused confusion. For example, Babb’s Mill is a meteoritic iron that was found in 1842 in Greene County, Tennessee, and was named alternatively Blake’s Iron, Greene County, or Troost’s Iron. Herein, when a former name appears in a quotation, I place the standard name in brackets following it—for example, Otumpa [Campo del Cielo], or the Pallas iron [Krasnojarsk]. Meteorites only occasionally carry the name of the individuals who found them; an example is Lutschaunig’s Stone, recognized by A. Lutschaunig in 1861 at Copiapo, Chile. Recently, because of the large number of finds on the barren Antarctic continent, meteorites receive an identifying letter-and-number combination. ALHA81005, for example, designates the fifth specimen found in 1981 at Allan Hills. It so happens that this particular meteorite was the first one recognized by scientists as having been catapulted from the surface of the Moon into an orbit that eventually crossed that of the Earth.

The first chapter and part of the second are devoted to a description of the underlying causes of eighteenth-century scientific disbelief or skepticism concerning the fall of meteorites, and to a review of the sequence of events that led to scientific acceptance of the phenomenon. One reason for my detailed analysis is that I hope thereby to counter misinformation and to correct errors, which through repetition have become rooted in accounts of or references to the actions or attitudes of eighteenth-century individual scientists or scientific bodies with respect to meteorite falls and finds.

A more important reason is that the episode furnishes a remarkable illustration of how a theory can dominate the minds of even the best scientists. This observation is, of course, not a new one. Historical accounts of the revolution in astronomy and physics that led to the rejection of the Aristotelian- Ptolemaic cosmos and to its replacement by that of Copernicus, Galileo, and Newton have clearly demonstrated how tenaciously scientists can cling to a familiar theory. With respect to the fall of meteorites, however, there were no religious beliefs that were possible influencing factors. The prevailing theory was that, apart from the celestial bodies, interplanetary or cosmic space did not contain any matter except the subtle and invisible aether. Therefore, neither stones nor irons could originate there. A subsidiary eighteenth-century theory affirmed what was true—namely, that stones or minerals could not be generated in the Earth’s atmosphere. Taken together, then, theory held that stones could not and did not fall from the heavens. It is also noteworthy that acceptance of falls occurred within a relatively brief period of time, when evidence of falls accumulated.

Even at the present time, meteorites are enigmatic objects. Scientists who study them are intrigued not only about their place of origin but also about the conditions that prevailed there and gave rise to their characteristic chemical and mineralogical compositions and structures. Meteorites have been investigated in various ways by scientists from a number of different disciplines. Karl Reichenbach in 1858 called attention to the fact that a meteorite is simultaneously a cosmological, astronomical, physical, geological, chemical, mineralogical, and meteorological object—that is to say, a meteorite can be viewed from many different perspectives. It is significant, then, that the various hypotheses proposed about the origin and history of meteorites have usually been intimately associated with the disciplines of the scientists advancing them. Mineralogists, for example, have elicited evidence from meteorites, which they have interpreted as favorable to one theory, and have discounted other evidence which astronomers believed convincingly supported an alternative theory. Only in the past three decades have scientists studying meteorites been equipped, because of their broad educational backgrounds, to consider meteorites from many of the perspectives mentioned by Reichenbach. The matter is important; viewing a natural or social phenomenon holistically is more likely to yield the most satisfactory explanation.

Scientists who investigate meteorites also face practical problems. The difficulties that nineteenth-century scientists encountered in completing reasonably accurate chemical analyses and in identifying the minerals in meteorites have now been largely overcome. However, as scientists have begun to study meteorites much more intensively during the past thirty years, new problems have arisen. I have described several of the obstacles in some detail, because the methods and techniques that scientists employ in efforts to arrive at accurate and reproducible results are sometimes overlooked. Painstaking (and often boring) experimentation, observation, and data gathering are, in my view, important components of science.

New instruments or instrumental techniques have had a distinct role in advancing knowledge about meteorites. I have not described these in detail, but trust that I have emphasized their significance. In the nineteenth century, the invention of the polarizing microscope and the technique of preparing thin sections of meteorites for detailed study provided mineralogists with the capability of identifying mineral constituents and structures. Moreover, improved telescopes aided astronomers both in the determination of cometary orbits and in the discovery of more and more asteroids. In the twentieth century, X-ray diffraction techniques, the mass spectrometer, the electron microprobe, and high-speed computers are among the numerous instruments and techniques that have significantly advanced scientific understanding of meteorites.

The recovery and collection of meteorites has been an important activity ever since scientists accepted the fact that they fell. I have described in chapter 6 the beginnings and development in the nineteenth century of several of the major museum collections in Europe and the United States. From the outset there was a lively market in meteorites, and it seems clear that shrewd Yankee dealers usually got the best of the bargain in transactions with their European cousins. Meteorite collections became symbols of civic pride and national prestige. High prices brought wails of anguish from scientists, who felt that the importance of meteorites for scientific research was becoming subservient to their preservation as precious relics.

How peoples at various times and in different places interpreted the appearance of meteors and fireballs and the fall and finding of meteorites is another important subject. Folklore and legends reflect cosmographical and religious beliefs, but the origins of some practices associated with the phenomena are buried in the distant past and still require clarification. We know that meteorites inspired intense fear among some peoples and were revered and worshiped by others. Yet in some primitive societies peoples used the irons to manufacture jewelry, tools, and weapons.

I am fully aware that I have given scant attention to some important aspects of meteoritics and have completely omitted mention of others. Some scientists, for example, have devoted a great amount of time to the study of the physics of the fall of meteorites through the atmosphere, how the attitude of the meteorite affects its loss of mass through ablation, and how crusts form. These investigations were of crucial importance in the design of reentry shields for space vehicles. Meteorite impact theory is another subject that deserves much more extensive treatment. I can only plead limitations of space for my failure in this respect.

Meteorites are fascinating objects that were formed during the birth of the Solar System. I hope that what I have included in this book will give readers a better understanding of how scientists and nonscientists alike have regarded and studied them.

1

Disbelief

Most eighteenth-century natural philosophers either did not believe or doubted that meteorites fell. This denial of the occurrence of an unusual but nonetheless genuine natural phenomenon has been an embarrassment to scientists, particularly because it persisted for about a century and therefore implies a serious error of judgment on the part of the scientific community. One explanation that appears to have gained general currency in scientific articles and texts about meteorites is that Enlightenment natural philosophers—especially the members of the Académie Royale des Sciences in Paris—were, in their justifiable desire to eradicate popular superstitions, overzealous, dogmatic, and too hasty in their dismissal of eyewitness reports.¹ The apparent parallel between the attitude of many twentieth-century scientists toward reports of unidentified flying objects or sightings of giant sea serpents and that of Enlightenment scientists toward meteorites has not escaped notice and has provoked defensive postures.² Indeed, this analogy has caught the attention of sociologists of science, one of whom has turned it to good account in a general critique of the reasons why the scientific community has failed to assess properly reports of anomalous events.³ All explanations to date of Enlightenment skepticism about the fall of meteorites share one defect: they fail to describe eighteenthcentury ideas about meteorology or the origin of minerals, and they do not give an adequate account of chemical knowledge and practice at that time. However naive the then prevailing theories as to the causes of atmospheric phenomena may appear by twentieth-century standards, eighteenth-century scientists had reasons for their disbelief—reasons apart from attributing reports of the fall of stones to superstition, exaggeration, or plain idiocy.

Four related topics require investigation. We should first review eighteenth-century theories of the causes of meteors and fireballs, and trace the sources of these ideas. Then we should examine theories as to how minerals formed in the earth and thunderstones in the atmosphere. Next, we should determine why scientists failed to make the connection between fireballs and meteorites, and why they were unable to distinguish meteorites from terrestrial stones and irons. Finally, we should summarize, insofar as the evidence

permits, the attitudes of eighteenth-century scientists toward reports of actual meteorite falls.

THE LEGACY OF ARISTOTLE’S METEOROLOGICA

The word meteors in the eighteenth century did not have the meaning it has at present. In his Lexicon Technician (1704), John Harris wrote that:

METEORS … are various impressions made upon the Elements, exhibiting them in different forms, … for the most part, they appear high in the Air, and they are either Fiery, Airy, or Watery. Fiery Meteors, are such as consist of a Fat, Sulphureous kindled Smoak, whereof there are several kinds: as Ignis Fatuus [will-of-the-wisp], Trabs [beam], Ignis Pyramidalis [aurora], Draco Volans [shooting star], Capra Saltans [leaping goat], Thunder and Lightning, etc. Airy Meteors, are such as consist of Flatuous and Spirituous Exhalations, as Winds, etc. Watery Meteors, consist of Vapours, or Watery Particles, by the Action of Heat separated from each other and variously modified as Rain, Dew, etc.

Meteors, then, were transitory atmospheric phenomena caused by the interaction in the air of terrestrial vapors or exhalations and consisting of elemental air, fire, or water. Their various manifestations depended on the particular kind of mixing process that had occurred in the atmosphere. Beams and goats were different types of fireballs. The former exhibited a broad, somewhat rectangular swath of flame across the sky. The latter appeared to be almost spherical and seemed to jump or swerve in its path.

This early eighteenth-century description and explanation of meteors stems directly from the meteorological theory established by Aristotle in the fourth century B.C. Aristotelian astronomical and physical theory had been destroyed by the scientific revolution of the sixteenth and seventeenth centuries. The planets with their satellite moons were shown to revolve in elliptical orbits around the sun in accordance with the law of universal gravitation. The spheres, supposedly holding the planets and the fixed stars in their daily orbits around the Earth, vanished, and the Earth with its Moon was assigned its proper place as the third planet distant from the Sun. However, Aristotle’s celestial element—the quintessence or aether—remained, both to transmit light from the Sun and the stars and as the medium by which the gravitational force was exerted throughout the universe. With a few exceptions, Aristotle’s teachings about phenomena occurring in the area between the Earth and the Moon— the sublunary region—were still respected. One major exception was the theory of comets, which Aristotle believed were meteors occurring in the higher regions of the atmosphere. Seneca disputed this notion in the first century A.D., but it was not until the late sixteenth century that observations, especially by Tycho Brahe, demonstrated conclusively that comets were astronomical phenomena. Another change in thinking had to do with the Milky Way, which Aristotle held was a sublunary appearance. A few medieval scholars, such as Ananis Shirakatsi of Armenia in the seventh century and Albertus Magnus in the thirteenth, considered the Milky Way as a collection of stars, and the telescopic observations of Galileo proved their ideas to be correct.

Aristotle’s views of sublunary phenomena, drawn principally from the teachings of Heracleitus of Ephesus, are united in the Meteorologica, written about 340 B.C. and considered authentic by most Aristotelian specialists. The work was well known in classical times and late antiquity. Books I through III were translated into Latin from the Arabic by Gerard of Cremona in the late twelfth century, and into Latin from the Greek by William of Moerbeke in the mid-thirteenth century. Its popularity thereafter is evidenced by the fact that almost three hundred manuscripts of the work are preserved in collections dating from the late thirteenth to the fifteenth century.⁴ In the early modern period, scientists were fully conversant with the Meteorologica; its influence was pervasive and continuing.

In the Meteorologica, Aristotle described just about every conceivable terrestrial and atmospheric phenomenon, and explained the cause of each. The classical four elements—earth, air, fire, and water—or, more precisely, the qualities that they embodied, lay at the basis of his teaching. The four opposing qualities were dry, moist, hot, and cold, and their intermixture produced hot-dry (fire), hot-moist (air), cold-moist (water), and cold-dry (earth). Ideally, each of the elements occupied its own sphere below the Moon. The celestial revolutions, however, and the heat of the Sun, which generated exhalations from the Earth, caused the intermixture of the elements and produced the changing phenomena both of the atmosphere and of the Earth. Aristotle’s writing style is pedantic and didactic. Nevertheless, it exudes self-assurance and confidence. His descriptions had just enough verisimilitude to make them palatable and convincing to naturalists for many centuries.

Aristotle explained that two kinds of exhalations arose from the Earth. One was a vapor, emanating from the water within and upon the Earth, while the other was dry, windy, and smoky, and came from the crevices in the Earth. The latter, called fire, rose to the top of the sublunary region, immediately beneath the circular celestial motion, and was inflammable. Wherever then conditions are most favorable, Aristotle wrote, this composition bursts into flame when the celestial revolution sets it in motion. What appeared in the sky when the material ignited depended upon the quantity and location of the material. If it extended both lengthwise and breadthwise, then one saw a beam; if lengthwise only, then torches or goats appeared. A goat threw off sparks; a torch did not. If the exhalation was separated into small parts, which were scattered about, then shooting stars resulted.

Sometimes, Aristotle continued, fiery meteors appeared much lower in the sublunary region, but originated from a different cause. Occasionally, the air contracted because of the cold, and the resulting pressure forced out heat, producing meteors that took a course similar to that of a projectile in motion. All these fiery meteors took place below the lunar sphere, Aristotle emphasized, a proof of which is the fact that the speed of their movement is comparable to that of objects thrown by us, which seem to move faster than the stars and sun and moon because they are close to us. The dry exhalations also caused lightning and thunder.⁵

Certain natural phenomena known to the Greeks supported the theory of exhalations. Smoke and steam issue from volcanoes, fumaroles and hot springs give off odorous gases, and combustible gases occur in mines. Moreover, fireballs do appear to be composed of combustible substances, and lightning bolts do cause fires. It is not surprising, then, that Aristotle’s theory of exhalations was accepted by most ancient writers who described meteors. Thus Seneca, though denying that comets were sublunary phenomena, followed Aristotle closely in other respects. Describing fireballs he wrote: Our sight does not discern their passing but believes the entire path is on fire wherever they fly. The speed of their transit is so great that its stages are not observable. Only movement as a whole is grasped.⁶ Pliny the Elder, about A.D. 75, stated that the sublunary region consisted of superior air and terrestrial exhalations, and from there emanated hail, hoar frost, the rains, the tempests, and the whirlwinds. Once in a while, he added, torches suddenly blazed forth, of which two kinds could be distinguished: the beautiful simple torches, which made long tails by burning in their anterior parts; and the bolides, which, burning from end to end, traced an extended wake of fire.⁷

Infrequently, there were alternative explanations of meteors. For example, in reporting the ideas of the atomist Epicurus, Diogenes Laertes, in the third century A.D., agreed that shooting stars might result when certain parts were expelled from a mixture of fire and air or when confined wind burst forth and ignited. But they might be caused, he wrote, by the mutual friction of the stars, or they might be due to the meeting of atoms capable of generating fire.⁸ However, the Aristotelian tradition proscribed both disorder in the celestial regions and atomistic explanations of phenomena, so such speculations did not provoke commentaries.

When we turn to late seventeenth- and early eighteenth-century explanations of fiery meteors, we find that the terrestrial exhalations still remain, although their characteristics have changed owing to contemporary chemical theory. John Woodward in 1695 declared that when the Sun’s power was great, it raised exhalations "out through the Mouths of Caverns, and through the Ordinary Cracks and Pores of the Earth, mounting them up, along with the Watery Exhalations, into the Atmosphere, especially Sulphur, Nitre, and the other more light and active Minerals; where they form Meteors; and are particularly the Cause of Thunder and of Lightning."⁹ In the Opticks, Sir Isaac Newton wrote that sulphureous Steams, at all times when the Earth is dry, ascending into the Air, ferment there with nitrous Acids, and sometimes taking fire cause Lightning and Thunder and Fiery Meteors.¹⁰ The sulphur and nitre here mentioned were not ordinary sulfur and niter. Sulphur, mercury, and salt were the three principles in the chemical tradition inaugurated by Paracelsus in the early sixteenth century. Sulphur was the principle of combustibility, variously characterized as moist, oily, clammy, fatty, and light. Nitre was a volatile salt, present in living things and chemically active in the vapor form."

In Paris, the academician Nicolas Lemery attempted to demonstrate the existence of sulfurous exhalations and their role in the production of fiery meteors by drawing an analogy from experiments.¹² In the heat of summer, he thoroughly mixed equal quantities of iron filings and pulverized sulfur in a large jar, added water, placed the container in a hole in the earth, and covered it with a rag and some soil. In about eight hours, the earth above the jar swelled, became hot, and developed fissures from which hot sulfurous fumes emerged. Soon these ignited, enlarging the crevices and dispersing a blackish yellow powder.

Lemery declared that the identical process took place within the earth as occurred in his experiment. Violent fermentation of iron and sulfur caused earthquakes, and the subterranean fires created by the sulfurous exhalations, if extensive and powerful enough, produced volcanoes on land and water spouts at sea. The sulfurous exhalations rising into the air became mixed with the clouds, and when greatly compressed, they ignited and appeared as lightning. Lemery anticipated the questions of how the sulfurous exhalations could be ignited in clouds formed of water, and why the flames were not extinguished when compressed. Sulfur, he explained, was an oily substance, not affected by water. It could be ignited in water and bum therein, just like camphor and other sulfurous materials. He granted that a portion of the vapor might be extinguished after a great detonation, but maintained that the more subtle portion of the sulfur—that more disposed to motion—continued to ignite.

To explain the source of the sulphur within the earth, Lemery performed another experiment. He poured, some esprit de vitriol (concentrated sulfuric acid) into a flask, diluted it with water, and warmed it gently. Then he gradually added iron filings. Soon there was an ebullition of white vapors that, when exposed to a lighted candle, ignited and also exploded. An important conclusion to be drawn from this experiment, Lemery wrote, was that the iron contains a great deal of sulphur …; necessarily then the sulphur of the iron filings having been rarefied and expanded by the spirit of vitriol is excited as an exhalation very susceptible to fire. Certainly, Lemery was misled by the confused state of contemporary chemical knowledge. He considered the vapor evolved in this experiment to be sulfurous exhalations; other mideighteenth-century chemists thought it was phlogiston; and eight decades later adherents of the new chemistry identified it as hydrogen gas. In any case, many scientists believed it to be the cause of meteors and fireballs.

In the mid-eighteenth century, scientists eliminated two types of fiery meteors, the aurora borealis and lightning, from the list of those supposedly caused by terrestrial exhalations. An aurora in March 1707, which was seen over most of central Europe, aroused scientific interest, and over 160 auroras were reported from 1716 to 1732.¹³ William Whiston in England and J. P. Maraldi in France adhered to tradition and explained them in accordance with the exhalation theory. There were, however, now alternative theories. Edmund Halley proposed that auroras resulted from the flow of luminous magnetic effluvia from the Earth’s polar regions. J. J. Dortous de Mairan supposed that the solar atmosphere extended outward from the Sun to such a great distance that it sometimes enveloped the Earth. When this occurred, the differing densities of the solar and terrestrial atmospheres produced auroras. Leonhard Euler made an analogy between auroras and the tails of comets, which, he wrote, glowed by reflected sunlight. Similar to comets, the Earth and the other planets had tails, whose particles accumulated at the poles and glowed by reflected sunlight at times when clouds did not absorb the solar rays.

Meanwhile, a number of scientists investigating electricity had postulated the electrical nature of lightning, and in 1752 Benjamin Franklin’s proposals and experiments proved this hypothesis to be true. Within a year John Canton suggested that the aurora was a passage of electrical fire from positive to negative clouds at a great distance, through the upper parts of the atmosphere, where the resistance is least.¹⁴ Though Canton’s suggestion was far off the mark, the notion that the aurora was a manifestation of electricity gained ground. Moreover, the idea was immediately extended to include meteors. In 1753, for example, Franklin asked his friend John Perkins of Boston to send him his thoughts on the cause of shooting stars. Perkins replied: As to shooting stars … I imagine them to be passes of electric fire from place to place in the atmosphere. … Electric fire in our globe is always in action, sometimes ascending, descending, or passing from region to region. I suppose it avoids the dry air, and therefore we never see these shoots ascend.¹⁵ Perkins’s reply demonstrates how rapidly hypotheses could be fashioned to offer explanations of phenomena in terms of a new discovery.

From mid-century onward, then, many scientists considered that meteors and fireballs were unusual manifestations of atmospheric electricity. Others thought that they were closely associated with auroras, which were, in turn, dependent in some manner upon electricity or magnetism. These ideas became strong competitors to the explanation of meteors as ignited terrestrial exhalations. But electricity did supply a vital ingredient to the exhalation theory, for it served as the most probable cause of the ignition of the atmospheric vapors.

THE GENESIS OF MINERALS AND THUNDERSTONES

The contents of the Aristotelian cosmos and the Newtonian one were almost exactly the same. The vast differences between the two lay in other areas: the distances, relative positions, and motions of the celestial bodies; the anisotropy of Aristotelian space versus the isotropy of Newtonian space; the function of the aether; and the fact that change occurred in the Newtonian cosmos—for example, stellar novae. But with the exceptions of the change in the status of comets from sublunar to astronomical phenomena, and the identification of the constituents of the Milky Way as stars, the contents of interplanetary space were identical. There were the stars, the Sun and its planets and their satellites, and the aether. There was nothing else.

Robert Hooke in his Micrographia (1665) succinctly expressed the prevailing conviction that no small bodies existed in interplanetary space. Hooke attempted to reproduce experimentally how the lunar craters that he had observed telescopically might have been formed. He dropped some bullets into a mixture of clay and found that they produced cavities similar to the lunar craters. However, he concluded that there was no probability that lunar craters would be formed by the impact of objects, for it would be difficult to imagine whence these bodies should come.¹⁶

Newton ruled out the existence of any but the great bodies, Fixed Stars, Planets, & Comets in the cosmos,¹⁷ stating that "to make way for the regular

and lasting Motions of the Planets and Comets, it’s necessary to empty the Heavens of all Matter, except perhaps some very thin Vapours, Steams, or Effluvia, arising from the Atmospheres of the Earth, Planets, and Comets."¹⁸ Gravitational theory dictated that each planet with any accompanying satellites was a self-contained entity, as if wrapped in a cocoon, and that interplanetary space was free of all matter except an invisible aether.

Newton’s ideas were reiterated throughout the eighteenth century. Euler, for example, reaffirmed that the universe contained only fixed stars, planets, and comets.¹⁹ The discovery of Uranus in 1781 by Sir William Herschel merely added another planet to the Solar System; it did not alter conceptions of the contents of interplanetary space. French scientists termed it le vide planétaire— the planetary void. Ernst Chladni described this idée fixe in 1794 in a paragraph that was both bitter and plaintive:

Now … the statement that in the reaches of space there exist in addition to the celestial bodies many smaller aggregations of matter appears to many so incredible that they repudiate [my] entire theory [of meteorites]. The incredibility of this statement is only pretended; it is not based on reason, but to a much greater extent on the fact that the statement is unusual, and also somewhat strange. For, if a statement were abstracted from accepted physical theory which read no material bodies exist in space other than the celestial bodies and the stars or some other thin elastic fluid, it would be considered just as preposterous as the statement: other material bodies exist there. Neither one can be proved on a priori grounds; observations must decide which is correct.²⁰

Chladni certainly went to the heart of the problem, but he underestimated the tenacity of the idea. In both Aristotelian and Newtonian theory, it was impossible for there to be small bodies wandering in interplanetary space which might occasionally invade the Earth’s atmosphere. The stones that were reported to have fallen must of necessity have a different origin.

To understand the eighteenth-century explanation of meteorites, we must again return to ancient authors. Legends and chronicles in both the Orient and the Occident record numerous instances of the fall of stones and other matter from the sky. Some of these occurrences and their implications for religion and mythology are treated in chapter 7. One fall, that at Aegospotami about 467 B.c., is important because several references to it were well known in early modern times.

According to Pliny, the Greeks honored Anaxagoras of Clazomene because on the basis of his astronomical knowledge he had predicted that on a certain day a stone would fall from the Sun. A stone, Pliny continued, as big as a wagon and of a burned color, did fall in broad daylight in Thrace near Aegospotami. Pliny acknowledged that stones occasionally fell from the sky, but ridiculed both the claim that Anaxagoras had predicted the event and the notion that stones might fall from the Sun.²¹ Plutarch, in his life of Lysander, mentioned the same event, but wrote that Anaxagoras foretold that the stone would come from one of the heavenly bodies on which a landslide or earthquake had occurred. Plutarch also cited another commentary, which stated that before the stone fell, for seventy-five days continually, there was seen in the heavens a vast fiery body. … But when it afterwards came down to the ground … there was no fire to be seen … only a stone lying big indeed, but which had no proportion, to speak of, to that fiery compass. … [This] proves those to be wrong who say that a rock broke off the top of a mountain, by winds and tempests … and fell to the ground.²²

In the last sentence, Plutarch undoubtedly referred to Aristotle and his followers. The Aegospotami fall is the only one mentioned in the Meteorologica in Aristotle’s discussion of comets. He wrote that when comets appeared frequently, the weather was dry and windy; when less frequent, there were excessive winds: For instance when the stone fell from the air at Aegospotami, it had been lifted by the wind and fell during the daytime: and its fall coincided with the appearance of a comet in the west.²³ Aristotle must have been at his wit’s end when he proposed this explanation. Evidently, he was certain that the fall of the stone had occurred. The stone could not have come from the aetherial regions as Anaxagoras asserted, because such an event would have compromised the perfection of the heavens, a cornerstone of Aristotle’s natural philosophy. Nor could it have come from the sublunary region, because Aristotle taught that stones were generated in the earth. The dry exhalation by the action of heat produced fossiles or infusible stones, whereas fusible stones including metallic ores were formed from moist exhalations.²⁴ His recourse was to have the wind lift the stone into the atmosphere from which it fell.

Although Plutarch found Aristotle’s suggestion ludicrous, Agricola in the sixteenth century accepted the idea. In De ortu et causis subterraneorum (1558), Agricola was concerned with the problem of how stones and metallic ores were formed in the earth. Along with the views of Theophrastus, Albertus Magnus, and Avicenna, Agricola presented the teachings of Aristotle, and he questioned the idea that infusible stones were produced from dry exhalations, because he thought they would be generated much more abundantly in the upper regions of fire than in the earth: Every time that comets, torches, flames, and meteors would be formed, stones or earths would fall; but as we see, this does not happen. Though, of course, authors of miraculous histories report that it has rained stones, yet Aristotle has made no mention of these; indeed, he himself writes that the stone which fell from the sky had first been raised high in the air by the force of the wind.²⁵ Agricola supported Aristotle’s explanation by reference to a nonferrous ore smelting process, in which lighter particles were driven into the furnace flue while heavier matter settled on the hearth. By analogy, he declared, fire in ore bodies in mountainous regions could result in scattering quantities of pumice and ash far and wide, into the fields below the mountains and even out to sea. But he maintained that if stones did fall, they must have a similar composition to those formed in the earth. The reason for Agricola’s equivocation was that he was acquainted with the portion of Avicenna’s Kitâb Al-Shitâ that reported the fall of several meteorites.

Avicenna, or Ibn Sina, the encyclopedic Islamic philosopher and physician, lived in what is now Iran from 980 to 1037. The portion of his works which concerns us was translated into Latin about 1300 as De congelatione et conglutinatione lapidum. In the few passages in which Avicenna treats meteorites, the first statement that catches the modern eye is his assertion that both iron and stony bodies fall—a clear indication that Avicenna was familiar with meteorites and knew there were different types of them. To be sure, Avicenna followed Aristotle in attributing their origin to the accidental qualities of coldness and dryness which fieriness acquires when it is extinguished, and he also reported that coppery bodies in the shape of arrowheads occasionally fell during thunderstorms. Most compelling, however, is his account of the fall of a large iron meteorite, which, he wrote, occurred in his own lifetime, and which he regarded, on unimpeachable evidence, to be true. Since the iron mass was too heavy to move, on the orders of the sultan a piece was cut off, but only after the breakage of many tools. This fragment was sent to the sultan, who ordered a sword to be made from it, but the task proved too difficult because of the character of the material.²⁶

Avicenna’s account clearly puzzled Agricola. He respected Avicenna as an authority, and dutifully informed his readers that Avicenna had documented the fall not only of stones but also of iron. But he wondered whether Avicenna might have been deceived by the authors of miraculous histories. Agricola was convinced that there were secreted within the earth various kinds of lapidific juices, each of which concreted into a specific type of stone, mineral, or metallic ore. For stones or iron to form in the air, the particular type of lapidific juice would have to be present, as well as some means by which the matter would be compacted. Unable to imagine how such conditions might occur, Agricola concluded his discussion by reiterating that it was much more acceptable to believe that stones had their origin in the earth.²⁷

For a century and a half, from Agricola’s time to the early eighteenth century, authorities differed as to whether stones could form in the sky. Ulisse Aldrovandi, an influential professor of natural sciences at the University of Bologna, supported Agricola’s reasoning and conclusion. He reported an account of the recent fall in the kingdom of Valencia of a stone mass filled with metallic veins, but he insisted that metals were only generated with considerable difficulty. Oily vapors were required together with a proper mixture of the mineral quality, as well as a place where the metallic material could remain for an appropriate period while it was being perfected. Such conditions, he emphasized, were found least of all in the air or in the clouds.²⁸

Others, however, maintained that stones could be generated in the air. Anselm Boece de Boodt, physician to Emperor Rudolph II, explained that stones sometimes formed in the atmosphere, when a very great exhalation composed of many terrestrial particles is hardened and confined in a small volume by the cold of the clouds that envelop it.²⁹ René Descartes also declared that very hard stones could be produced in clouds, but that heat was the agency in the form of lightning. The sediment at the bottom of a jar of rainwater gave evidence that there was earthy material in the clouds, and experience proved that if a mixture of this earth, sulfur, and saltpeter was heated, it would form a stone.³⁰ Other Cartesians supported this hypothesis, although Jacques Rohault was puzzled that a thunderstone had not been seen to fall on some occasion in one of the streets of this great city [Paris], or in some courtyard or on the roof of some house.³¹

After 1700, however, there was general agreement that stones did not form in the atmosphere. Nicolas Lemery was apparently the leader in the opposition to the notion, because his dictum was cited often in the following eight decades. It was not absolutely impossible, Lemery wrote, that violent winds rising into the clouds might at times carry along stony or mineral matter, which was softened and compacted by heat to produce what were termed thunderstones. But, he added, there would be much more reason to believe that it came from mineral matter in the earth itself and formed by the ignited sulfur of lightning, than to suppose that the stone was generated in the air or clouds and ejected along with the thunder.³²

As already noted, Franklin’s electrical theory of lightning superseded Lemery’s notion that ignited sulphur was the cause. However, the idea that meteorites originated in situ by the action of lightning became one of the leading explanations of meteorites falls and finds for the rest of the eighteenth century. Diderot’s Encyclopédie stated that thunderstones were merely mineral matter that had been fused or scorified by the action of lightning.³³ Johann G. Wallerius, probably the most influential mid-eighteenth-century mineralogist, declared that thunderstones were neither raised into the clouds by winds nor generated there, but produced on Earth by the action of lightning.³⁴ In a letter written in 1767 to Benjamin Franklin, Giambatista Beccaria attributed the Albareto fall, reported by Domenico Troili, to the agency of lightning: The soil at Modena is everywhere full of the nearby water. Wherefore the bolt, driving through the stone, which is metallic, into the water beneath, should scatter the water and hurl the stone into the air while covered in its own flash, so that it be not seen until afterwards, when it falls back down.³⁵ It is hardly surprising, then, that the committee of the Académie Royale des Sciences— composed of Fougeroux de Bonderoy, Cadet de Gassicourt, and Lavoisier, and charged with the investigation of the Luce fall of 1768—concluded that the stone must have been struck by lightning, and that the peasants who testified to its fall had been deceived.³⁶

The reality of thunderstones, supposedly formed in the clouds and cast to earth, was attacked from another quarter—that of archaeologists and natural historians. Some of these so-called thunderstones or pierres de foudre were, in fact, unusually shaped crystals of pyrite or marcasite; others called cerauniae were Stone Age axs, hammers, or spearheads; and still others, termed brontia or ombria, were fossil echinoids or sea urchins. The first detailed treatise on such objects was written in 1565 by Conrad Gesner of Zurich, a botanist and natural historian, and included sketches of ombria and cerauniae. Four of the latter, either pyramidal or oval-shaped with holes, are obviously hammers or axs. Because all cerauniae had recognizably geometric shapes, Gesner was puzzled about a stone, which fell from heaven in the year of our Lord 1492, which may be seen suspended in the church at En- sisheim. … It had (I think) no definite shape (unless by chance it was diminished by many fragments having been taken away).³⁷ Here Gesner described a genuine meteorite, but was so convinced that thunderstones should have figured shapes that he speculated that fragments detached from the stone probably destroyed its geometric form.

A few decades later, Michele Mercati, director of the Vatican botanical garden, voiced the suspicion that cerauniae were stone implements made by humans who were unacquainted with bronze or iron. His view was not widely known in the seventeenth century, because his work on minerals and fossils was not published until 1717. However, others had the same idea. The English antiquarian, Sir William Dugdale, stated his belief in 1656 that cerauniae had been formed by human hands. About the same time, Olaus Wormius, a Danish physician and archaeologist, wondered about some Danish flint blades: If flint could be easily pierced, you might swear this object had been fashioned rather by art than by nature. And about flint daggers, he wrote: Considering which I am uncertain whether they are works of art or of nature. Are they what may be referred to as cerauniae, or are they what may be considered to have been old swords?³⁸

Wormius’s comments reveal what puzzled him and other archaeologists. The civilized peoples of the early modern period could not conceive that humans had ever expended the patience and care or possessed the dexterity and skill to fashion such tools from hard stone. But when stone implements were sent back from the Americas to Europe, understanding rapidly followed. In 1723, Antoine de Jussieu, referring to stone specimens of an ax, wedge, and arrowheads obtained from Indians of the Caribbean and of Canada, explained in a memoir to the Paris Academy of Sciences how such implements were made without the use of any metal tools. Throughout his memoir, Jussieu stressed that the so-called thunderstones found in Europe were also the tools and weapons of the early inhabitants and did not have a celestial origin.³⁹

Further evidence discounting the atmospheric origin of thunderstones rapidly accumulated. Nicolas Mahudel in 1734 gave a detailed description of chisels, hammers, hatchets, picks, digging tools, and lances, all presumed to be cerauniae, and added that the usage of such implements continued well after the discovery of bronze and iron. Brontia, he stated, were petrified echinites, and other alleged thunderstones were figured marcasites and pyrites.⁴⁰ Both J. B. L. Rome de 1’Isle and René Just Haüy gave good descriptions of the latter pierres de foudre. Romé de 1’Isle in 1767 wrote that they were large globular specimens of pyrite with spear-shaped protuberances projecting from their surfaces, forming thereby stellated cavities. In 1801 Haüy named this particular type of pyrite fer sulfuré radié. This variety, he wrote, was usually found in globular or ovoid crystalline masses. The lower portions consisted of pinnacle-shaped projections pressed against one another and directed toward a common center. The upper portions, jutting out from the surface, were usually the halves of an octahedron, sometimes cubic-octahedrons, and occasionally cubes bearing striations in three directions.⁴¹ It is apparent that both Romé de 1’Isle and Haüy were describing massive but not unusual specimens of iron pyrite or marcasite belonging to the isometric system.

In the early eighteenth century, then, there was a convergence of two trends. The first was the growing conviction of chemists and mineralogists that it was impossible for stones to be generated in the atmosphere or in the clouds, whether or not they were thunderheads. The second trend emerged from the studies of early paleontologists, archaeologists, and mineralogists, which tended to prove that the stones alleged to have fallen during thunderstorms were either fossils, ancient stone implements, or crystal masses of a common mineral. One can begin to understand the increasingly militant skepticism among scientists concerning the fall of stones from the sky. But belief was also undermined by reports, both ancient and modern, of the fall of other objects, which eighteenth-century scientists could only regard as fabulous.

Pliny, for example, wrote that rains of milk and of blood had been recorded in the consulate of Manius Acilius and Gaius Porcius (114 B.C.) and on many other occasions; that there had been a rain of flesh in the consulate of P. Volumnius and Servius Sulpicius (461 B.C), which did not putrefy and which carrion did not eat; and that in the consulate of L. Paulus and C. Marcellus (50 B.C.) there was a rain of wool and another of kiln-dried bricks. Interspersed among these reports were accounts of other falls that may well have been meteorites, such as a fall of iron in Lucania in 54 B.C. and the fall of the stone at Aegospotami, mentioned previously.⁴²

Reports of such events continued to accumulate through the centuries. Rains of blood were announced to have fallen in the ninth, fifteenth, and on several occasions in the sixteenth century. A burning object was said to have fallen in 1110 into a lake in Armenia, making its waters bloodred, while at the same time the earth nearby was cleft in several places. In 1618 a shower of blood occurred in Styria, and a red rain fell in 1638 at Toumay, in 1640 at Brussels, and in 1645 at Bois-le-duc. Gelatinous matter was reported to have fallen in 1718 in India.⁴³ And on 31 January 1686 at a village in the province of Courland [Latvia], a large quantity of a paperlike substance fell from the sky during a snow flurry.⁴⁴

In a memoir read to the French Academy of Inscriptions and Belles Lettres in 1717, Nicolas Frérét attempted to distinguish between fact and fancy in these reports. He dismissed the rains of flesh, asserting that it could not have been flesh, and attributed the red blots seen on the ground, which seemed to give evidence of showers of blood, to the chrysalises of caterpillars. A fall of money reported by Dio Cassius in his history of the reign of Severus, Frérét said, was undoubtedly mercury, which had been elevated as a vapor and fell when it was congealed by the cold. As for the fall of stones, his belief was that they did occasionally fall, and that they had been ejected from volcanoes and might be transported in the air for hundreds of miles and for long periods of time before they fell to earth. To support his position, Frérét referred to a report by Dio that in the reign of Vespasian an eruption of Vesuvius carried ash as far as Egypt, and cited Cardinal Bembo, who, in describing an eruption of Etna in 1537, wrote that its ash was transported more than 200 leagues from Sicily.⁴⁵

Frérét’s explanation of meteorites as volcanic ejecta was the last resort for those who believed reports of the fall of stones, and it appears occasionally in eighteenth-century scientific literature. It was used to explain the presence of the Pallas iron [Krasnojarsk] on a high ridge of a remote Siberian mountain. Don Rubin de Celis, who in 1783 rediscovered a portion of the Campo del Cielo iron meteorite, weighing by his estimate about fifteen tons, concluded in his report that it was the product of a volcanic eruption.⁴⁶ Domenico Troili employed a variation—ejecta from a nearby vent in the earth—to account for the Albareto fall near Modena in 1766, a theory rejected by Beccaria. The idea of a terrestrial volcanic origin of meteorites also played a central role in the controversy surrounding the Siena fall in 1794, which occurred, coincidentally, only 18 hours after an eruption of Vesuvius.

Eighteenth-century physical theory dictated that pieces of matter could not fall to earth from interplanetary space, because only the great celestial bodies and the aether existed there. The theory of mineral formation eliminated the possibility that stones formed in the atmosphere. There was more than sufficient proof that stones alleged to have fallen from the clouds were Stone Age tools, fossils, or unusual mineral crystals. That rains of blood, milk, or money had occurred was too much for Enlightenment scientists to stomach, and the tales of such miraculous events weakened the credibility of reports that stones had fallen. Nevertheless, it was scientific theory that played the leading role in the disbelief and skepticism that scientists displayed.

DILEMMAS ABOUT FIREBALLS AND GENUINE METEORITES

During the eighteenth century, there were 189 reports of fireballs, and two- thirds of this number appeared after 1750 (fig. 1). In the first decade of the nineteenth century alone, after meteorite falls were accepted, the number of reports increased to 65. Such reports depended not only upon the occurrence of the phenomena but upon population density and a good level of education and information as well.⁴⁷ Thus there was an increasing awareness of the phenomenon as the century progressed. The sizable number of fireballs seen

Fig. 1. Numbers of fireballs reported by decades, 1700-1809. From Greg (1860).

in the 1750s and 1760s elicited scientific interest in them. John Pringle published a comprehensive report in the Philosophical Transactions, and the French Academy of Sciences instructed Jean-Baptiste Le Roy to study the phenomenon of fireballs in general and the bolide of July 1771 in particular. In Pringle and Le Roy’s reports, some of the more important impediments to understanding the nature of fireballs and the reasons why fireballs were not connected with the fall of meteorites become clear.

John Pringle was a physician, a fellow of the Royal Society, and its president from 1772 until 1776. The fireball about which he reported appeared after nightfall on 26 November 1758, and his account was based on the testimony of more than a dozen witnesses. Observers first saw it over Cambridge at an estimated height of 90 to 100 miles. It moved in a west by northwest direction and suddenly disappeared over Fort William in the shire of Inverness, where witnesses judged its altitude to be 26 to 32 miles. Over Auchenleck, part of its tail seemed to break off, and it rose and dipped in its course, which Pringle suggested was due to its impingement on more dense air at the lower elevations, in the same manner as a cannon ball by water, when it strikes in a very oblique direction.

Pringle thought that the velocity of the fireball was almost incredible, since it traversed 324 miles in 13 seconds, or 25 miles per second. Estimates of the diameter ranged up to 2 miles, but Pringle, considering that the observers’ imaginations had exaggerated its size, reckoned that its diameter was only 0.5 mile. Some witnesses testified that they heard a hissing noise as the fireball passed, but Pringle dismissed these accounts, stating that it was a deception of that kind which frequently connects sound with motion. Charles Blagden, two decades later, claimed that the noise was physical not psychological, though he confessed he was unable to explain it. Twentieth-century physicists have studied the hissing noise, which sometimes accompanies the passage of a fireball, and a recent explanation is that the fireball may, because of the highly energetic wave turbulence, radiate very low-frequency electromagnetic energy, which excites surface acoustic waves in surrounding objects.⁴⁸

Witnesses at a distance of 75 miles heard the sound when the tail exploded, and compared it to thunder or to volleys of heavy artillery. Pringle thought that the sound gave evidence that the body or at least its surface was solid, because sounds are either produced by the quick and violent percussion of hard bodies upon the air; or by the sudden expansion of an elastic fluid, after being condensed within some solid substance. Also, after the explosion the body retained its form, so presumably the burning matter was vented through apertures in a hard crust. The velocity of the fireball and the intensity of its light, Pringle wrote, also favored the idea that the body was solid.

Pringle abruptly dismissed the notion that the phenomenon was lightning, stating that it was based wholly upon the velocity of those balls of fire. Further, he wrote, all observations argued against the prevailing hypothesis, advanced by Halley in 1719, that such bodies consist of sulphureous vapours arising from the earth. There was no experimental evidence that such vapors possessed innate levity, as Halley had postulated, which would permit them to rise into the absolute vacuum above the atmosphere. Because of the extreme cold of the higher regions of the atmosphere, the volatility of the vapors would be decreased, and how ignition occurred had not been explained. Finally, attraction should cause the vapors to assume a spherical rather than the lenticular form exhibited in the current instance, extending in a straight line of equal breadth for a distance of some 400 miles.

Pringle, however, did think that another notion of Halley’s, expressed in 1714, had some merit—namely, that a meteor must be some Collection of Matter form’d in the Aether.⁴⁹ Because of the great velocity of the fireball in the atmosphere, though, he thought Halley was wrong in supposing that a fortuitous Concourse of Atoms met with the orbiting Earth before being attracted to the Sun. He also rejected Halley’s suggestion that such meteors actually came to the ground. The descent of fireballs below the horizon, Pringle wrote, gave the impression that they fell to earth, and the explosion, heard only much later, was mistaken for the noise of the fall. He continued: Hitherto we have had no certain proof of their fall; and it is to be hoped, that their motions, like those of the comets, have been so regulated at first by a governing Power, that we have nothing to apprehend from their aberration. … If it is then probable, that these balls of fire come from regions far beyond the reach of our vapours; … surely we are not to consider them as indifferent to us … but rather as bodies of a nobler origin, possibly revolving about some center.⁵⁰

In Pringle’s account, then, there is an expression of perplexity concerning the incredible velocity and tremendous apparent size of fireballs; a rejection of hypotheses attributing the phenomenon either to the ignition of terrestrial vapors or to the action of lightning; a denial that fireballs fall to earth; and suggestions that fireballs might originate beyond the atmosphere and might be related to comets.

The fireball that Le Roy described in his report first appeared at about 10:30 p.M. on 17 July 1771 over Sussex County, England; traveled in a south-southeast direction over the English Channel, lower Normandy, and the He de France directly above Paris; and exploded and disappeared near Melun, about 30 miles away (fig. 2). The estimated height when first seen was about 50 miles, and at the moment of explosion it was 25 miles. Most observers thought that the duration of the phenomenon was 4 seconds, during which time the fireball traversed 180 miles, but Le Roy arbitrarily increased the elapsed time to 10 seconds to arrive at a more credible velocity of 18 miles per second. From the direction and height of the globe, Le Roy wrote, "there is almost no doubt that it was formed [formé] above the shores of England … it is there that it originated [il a pris naissance]." Here Le Roy’s language seems to indicate a bias toward the atmospheric origin of fireballs.

It was the size of the fireball that most astounded Le Roy; his estimate of the diameter, which again was far less than those given by eyewitnesses, was 0.6 miles. What city, he exclaimed, "could escape a general conflagration and total ruin, if a similar globe fell within its walls!