CHAPTER 2—PART 1

UNLOCKING THE "UNKNOWN MYSTERY OF THE TRUE NATURE OF THE HEAVENLY BODIES"

It has long been accepted by historians of astronomy that William Huggins underwent a dramatic change in his research interests and methods in the early 1860s.  Such an interpretation is encouraged by his own vivid retrospective narrative:

I soon became a little dissatisfied with the routine character of ordinary astronomical work, and in a vague way sought about in my mind for the possibility of research upon the heavens in a new direction or by new methods.  It was just at this time ... that the news reached me of Kirchhoff's great discovery of the true nature and the chemical constitution of the sun from his interpretation of the Fraunhofer lines.

This news was to me like the coming upon a spring of water in a dry and thirsty land.  Here at last presented itself the very order of work for which in an indefinite way I was looking -- namely, to extend his novel methods of research upon the sun to the other heavenly bodies. A feeling as of inspiration seized me:  I felt as if I had it now in my power to lift a veil which had never before been lifted; as if a key had been put into my hands which would unlock a door which had been regarded as for ever closed to man -- the veil and the door behind which lay the unknown mystery of the true nature of the heavenly bodies.¹

This statement is a favorite among chroniclers of the origins of astrophysical research.²  Not only does it possess all the authority of an eyewitness account, but its wry understatement of the deadly tedium faced by serious observers pursuing a nightly regimen of traditional astronomical mapmaking and clockwatching struck a chord with turn-of-the-century readers who had spurned such drudgery themselves and opted for a career in astrophysics.  It was invigorating to trace one's professional roots to a pioneer of such vision and daring -- someone obviously on the inside track who was able correctly to assess the state of affairs and act to rectify things.

But I shall argue in this chapter that Huggins was not the prescient genius his statement may suggest.  He could describe the events which influenced his early career choices in such clearcut terms because he was writing about them in 1897, some thirty-five years after the fact.  The image of a sudden leap forward with no turning back called up by this passage does not mesh with the patchwork of observations that Huggins recorded between 1860 and 1865.  His transformation was in reality a complex and gradual process which, as in many other retrospective accounts, became simplified and foreshortened when viewed with the long focus of his own mnemonic lens.

Chapter 1 charted the evolution of William Huggins' observational and interpretational sophistication as revealed in his earliest notebook entries.  In this chapter, I shall bring to light the elements of his individual response to the introduction of the spectroscope as an instrument with mensurational capabilities suitable to a program of rigorous astronomical research.  I shall investigate the strategies he employed to build his reputation among his fellow astronomers, both amateur and professional, and to acquire the recognition and respect of eminent men of science.  Beginning with a description of the British astronomical community in 1860, I address the following questions:  What were the set of problems which challenged the ingenuity of its members and defined the boundaries of acceptable research? what theories, methods, and instruments constituted legitimate means for attacking these problems and interpreting results? and finally, what standards determined which observational interpretations were reliable and confirmable descriptions of Nature?

Then, I shall present information concerning the sequence of events surrounding the British reception of Gustav Kirchhoff's radiation law in order to explore how a novice amateur astronomer like Huggins may first have become aware of Kirchhoff's work and the implications of his interpretation of spectroscopic observations.  This will make it possible to understand better how Huggins initiated his plan to apply Kirchhoff's method to the stars and nebulae.

Following an analysis of Huggins' strategies for obtaining legitimating recognition for his spectroscopic work from influential members of the Royal Astronomical Society, I shall conclude with a discussion of Huggins' election to fellowship in the Royal Society as the culminating event of this intermediate phase in Huggins' career as a serious amateur astronomer.

The Astronomical Agenda:  1830 - 1870

In the mid-nineteenth century, practicing astronomers in Britain came from a wide variety of backgrounds.  There were, of course, a few who earned their living in observatories and/or teaching astronomy.  But a large number were individuals with sufficient funds from other sources who were never paid for their astronomical contributions and, thus, were amateurs in the true sense of the word.  Many of these amateurs had no university training.  Their interests, abilities, resources, and personal ambition led them to pursue astronomy with varying amounts of rigor and seriousness ranging from dilettante to full-time observer.  Representatives of all these types can be found among the ranks of the Royal Astronomical Society in the middle of the nineteenth century.  It is within the institutional confines of this diverse group that William Huggins found his first opportunities to test his astronomical mettle.³

A variety of interests and concerns drove the mid-century astronomical enterprise.  New discoveries were made, old problems were seen in new ways, new instruments were designed, and new methods devised giving the astronomical research agenda of this period a protean quality which was particularly appealing to the diverse amateur contingent.  At the same time, there was a change in the collective sense of purpose among non-professional British astronomers.  This shift in definition of the goals and aspirations of those who would contribute to existing knowledge of the heavens took place while William Huggins was taking his first steps in astronomical research, but it had been years in development.

In 1833, John Narrien, professor of mathematics at the Royal Military College, London, published an acclaimed account of the history of astronomy up through the work of Isaac Newton.⁴  While devoting much of his book to an explication, based on original sources, of the progress of astronomy from ancient times through the early modern era, he both prefaced and concluded it with a discussion of then-current astronomical problems.

Narrien described two types of astronomical research:  Practical astronomy devoted to calendrical improvement, and physical astronomy motivated by a desire to further elucidate Newton's mechanical laws.⁵  In addition to refining measures of the aberration of starlight, searching for evidence of stellar parallax, and improving achromatic telescopes and chronometers,⁶ astronomers, in Narrien's view, needed to continue work on the three body problem, precession, and planetary perturbations.⁷ It was a waste of time and energy to construct telescopes larger than those currently in use because larger instruments are subject to increased "derangements."⁸  In terms of astronomical investigation, Narrien concluded that "human ingenuity will, probably, in future, be able to accomplish little more than an improvement in the means of making observations, or in the analysis by which the rules of computation are investigated."⁹

Moving forward to the time when Huggins became a Fellow of the RAS, we find that Robert Grant's History of Physical Astronomy (1852), mentioned briefly in the last chapter, supplies useful insight into the problems which interested both professional and amateur astronomers in the mid-nineteenth century.  Grant devoted the book's final chapter to a discussion of current problems in astronomy.¹⁰  The success of Lord Rosse's efforts in constructing large reflecting telescopes in the 1840s left Grant more optimistic than Narrien had been twenty years earlier concerning the potential for new knowledge to be gained from the use of such instruments.

Grant's enumeration of contemporary problems in astronomy included the need to substantiate claims of having observed changes in the structure and appearance of various celestial bodies, to determine with greater certainty the mass of the newly discovered planet Neptune, to measure stellar parallax, to determine the direction and magnitude of the solar system's motion in space, to uncover the nature of nebulae, and to acquire sufficient information concerning the distribution of stars in space to allow some understanding of the structure of large-scale stellar systems.

The eleventh edition of the authoritative Outlines of Astronomy by John F. W. Herschel (1792-1871) included a number of prefaces to earlier editions thus providing a sweep of the gradual shift in astronomical research interests from the 1840s to the 1870s.  Viewed by his colleagues as one of the greatest scientists of his day, John Herschel was the son of the renowned astronomer William Herschel. He was respected in Britain and abroad for his own contributions to astronomy including surveys of double stars as well as continuing his father's projects of star-gaging and cataloguing of nebulae.  The younger Herschel was among the founding members of the RAS and served three times as its president.

In the preface to the first edition of his Outlines (1849), Herschel echoed the statements of Narrien concerning the future of astronomical research and pointed to the recent discovery of Neptune as evidence for the importance of the continued study of planetary perturbations.¹¹  The book's fifth edition (1858) drew the reader's attention to recent improved determinations of the mass of the earth, Foucault's pendulum experiments, William Thomson's speculations on the origin of solar heat, and the continuing question of the moon's habitability.¹²  The emphasis on these problems was considerably diminished in the tenth edition (1869), however.  After remarking on the "vast and unexpected" information recently gathered concerning the "physical constitution of the central body of our own [solar] system,"¹³ Herschel noted that "the application of spectrum analysis has disclosed the amazing fact of the gaseous constitution of many of the nebulae" thus permitting for the first time "a real line of demarcation between nebulae proper and sidereal clusters."¹⁴  He further advertised the advantages afforded astronomical research through the application of this "optical science to chemistry" by noting the identification of terrestrial elements in the sun and the measurement of a star's motion in the line of sight.¹⁵

An evolution in the sense of purpose among practicing British astronomers during this period is evident in statements issuing from the RAS itself.  In 1827, for example, in one of the earliest published addresses on the award of the Royal Astronomical Society's Gold Medal, John Herschel, then President of the RAS, spoke of the astronomer's mission as one involving the relentless quest to fix each star in its proper celestial location for the benefit of astronomy, geography, navigation and surveying.  The eyes and instruments of many working together would make the task less onerous, he claimed, hence the value of the Society in coordinating such efforts.¹⁶  Thirty-five years later, RAS President John Lee, delivered another Gold Medal address, on the occasion of its award to the amateur astronomer Warren De La Rue, for his pioneering work in celestial photography. Rather than invoke the value of a concerted effort by all astronomers to effect the completion of one grand project as envisioned by Herschel, Lee praised the division of labor among those drawn to study the heavens which encouraged the pursuit of complementary research agendas based on individual skills and interests.¹⁷

Lee's sentiments were reiterated in the pages of the Society's Monthly Notices.  In 1863, Arthur Cayley, who had recently become the journal's editor, introduced a section entitled "The Progress of Astronomy" as part of the annual "Report of the Council."¹⁸  By 1865, this section was both expanded and topically subdivided, allowing more details of the ongoing work of individuals to be communicated.¹⁹

Another indication of the growing diversity in the RAS was the success of a new publication, the Astronomical Register, which began publication in January 1863.  This journal was started by Sandford Gorton, a relative newcomer to the RAS, having only been elected to Fellowship in 1860.²⁰  By publishing "stray fragments of information" gleaned at RAS meetings and the substance of "passing conversations" deemed too insignificant to appear in the Monthly Notices, Gorton hoped this new journal would serve as a "medium of communication for amateurs and others."²¹  To that end, he announced that each monthly issue would include a table of "occurrences" so that all might prepare in advance for forthcoming celestial events in addition to a summary of Society meetings, including excerpted transcriptions of discussions arising from the presentation of papers for those unable to attend.  William Huggins was listed as a subscriber by June 1863.²²

The "Report of Council to the Forty-first Annual General Meeting" published in the Monthly Notices portrays the RAS in the year 1860, particularly its amateur element, as a vibrant and enthusiastic collection of individuals excited about the numerous reports of the recent solar eclipse, about the use of photography to capture stellar as well as lunar and solar images, and about the discovery of several new minor planets.  Huggins' 1897 recollection of astronomy being mired in "routine" may say more about the agenda of the mid-century professional astronomer and its rigid adherence to a program of precision timing and mapping than that of the amateur community of which he was a part.  Before turning to Huggins' response to the announcement of Kirchhoff's radiation law, however, I shall present a brief overview of its reception by the wider collection of British physical scientists, both professional and amateur.

"The astronomer ... must come to the chemist."

In 1887, the historian of nineteenth century astronomy, Agnes Clerke could look back over the previous quarter century and talk about the founding of a whole new science which she called "astronomical or cosmical physics."  She saw this new science as a youthful variety of astronomy, markedly different in goals as well as methods from its older mathematical cousin.  "It is full of the audacities, the inconsistencies, the imperfections, the possibilities of youth," she wrote.  "It promises everything; it has already performed much; it will doubtless perform much more."²³  And she identified William Huggins as one of stellar spectroscopy's principal founders.²⁴

In Britain, astronomical physics did not grow out of epistemological or methodological concerns facing mid-century professional astronomers -- the handful of celestial mechanicians who set their goals and measured their accomplishments against the problems set by Greenwich, Paris, Berlin, and Pulkova.²⁵  The arduous task of mapping the stars with the precision required to track the motion of the planets left them little time for idle speculation on their physical and chemical structure.

By the same token, this new agenda for astronomical research did not arise out of a Malthusian struggle among professional astronomers for a limited supply of new research problems, resources, priority or prestige.  Nor did it develop in response to growing dissatisfaction in the ranks with the prevailing professional research agenda.  In fact, the emergence of astronomical physics in Britain was not a product of any of the usual social, economic or intellectual processes commonly seen as playing a role in infusing new research agendas into existing disciplines.²⁶ It got its start among a handful of individuals operating outside the boundaries of professional astronomy.

John Lankford has drawn attention to the important contributions of amateur astronomers to the development of this new research agenda, aptly referring to them as the "risk-takers of science."²⁷  A. J. Meadows has noted the contributions of "scientists with wide-ranging interests" which made possible the "cross-fertilization of ideas that led to an interest in astrophysics."²⁸  Of particular importance in this process, according to Meadows, were individuals possessing little or no mathematical training.  Karl Hufbauer has refined this further by pointing out that training was not the sole limiting factor.  He has argued that quality of instrumentation also served to select those individuals who were capable of contributing fruitfully to the traditional astrometric agenda.  Thus, in Hufbauer's scheme, a subgroup of professional astronomers, whom he has called "marginal professionals," and those amateur astronomers, like William Huggins, who were unable to contribute to the collection of positional data because of the "inadequacies of their astronomical training and/or the limitations of their astronomical instruments" sought alternative ways to participate in astronomical research.²⁹

I prefer to use the term "peripheral" instead of "marginal."  The original use of the term "marginal man," as introduced by Robert Park, was intended to help describe the difficulties faced by an individual caught between two conflicting sets of social norms.³⁰  Rather than freeing the individual by liberating him from normative constraints, such a conflict paralyzes him making it difficult or impossible to function satisfactorily in either realm.  Over the years, the term has taken on a life of its own, however, and is now used in the sense that Hufbauer uses it, namely to refer to an individual with loose social, cultural or intellectual ties to a given group and who, as a result of this lack of restrictions on his thinking, finds himself in a positive and open environment conducive to creative and constructive action.  I believe the term "peripheral" permits that same inference to be generated without the potential misunderstanding which may arise as a result of the misapplication of a term developed to describe something completely different.³¹

While I agree that William Huggins (see Figure 9) operated as an independent observer on the periphery of professional and institutional science, this did not free him entirely of constraints on his work -- it just imposed a different set of rules from those facing professional astronomers.  Huggins took deliberate steps to establish himself as an up-and-coming serious amateur.  He may have been a risk-taker, but in keeping with his entrepreneurial background, his risks were calculated to maximize success.

Figure 9.  William Huggins (Photograph from the Royal Astronomical Society Library, Add MS 94, 1.)

As we saw in chapter 1, Huggins constructed an observatory building attached to his home, he purchased a high quality, large aperture, refracting telescope from a prominent and experienced serious amateur, and he contributed reports from his observatory for publication in the Monthly Notices.  These actions demonstrated both a commitment and a willingness to conform to the Royal Astronomical Society's pre-existing performance standards in order to attain prestige and recognition from his Fellows.  William Huggins also sought the special acclaim accorded those fortunate enough to make a notable discovery.  Recall that Huggins, not wishing to sound too presumptuous concerning his personal ambitions, wrote in his retrospective that he searched, in those early days of his career, "in a vague way" for some "possibility of research upon the heavens in a new direction or by new methods."³²  In astronomy, such discoveries were not restricted to the professionals.

On 20 October 1859, Gustav Kirchhoff presented a paper on the sun's Fraunhofer lines to the Berlin Academy.  It appeared in English translation six months later in the Philosophical Magazine.³³  This seminal paper, whose English title read simply, "On Fraunhofer's Lines," recounted Kirchhoff's recent collaboration with the chemist Robert Bunsen to investigate the perplexing dark lines which interrupt the otherwise continuous solar spectrum.  In his paper, Kirchhoff offered both a chemical interpretation of these lines and a hint of a physical explanation to account for them.

For some time, Kirchhoff had been working in collaboration with Bunsen, carefully studying the spectra of light generated by various salts placed in flames and between electrodes.  Together they determined that an individual metal produces its own characteristic pattern of bright spectral lines when it is burned.  When white limelight is passed through a cool vaporous cloud of this same element, the continuous rainbow of the white light is broken by dark absorption lines arranged in precisely the same spectral pattern characteristic of that element.  Following these experiments, Kirchhoff made additional observations of the solar spectrum formed after sunlight had passed through a flame containing table salt.  He concluded that the dark Fraunhofer lines in the sun's spectrum "exist in consequence of the presence, in the incandescent atmosphere of the sun, of those substances which in the spectrum of a flame produce bright lines at the same place."³⁴

Henry Roscoe (1833-1915), Professor of Chemistry at Owens College in Manchester, was a former student and collaborator of Robert Bunsen.  Roscoe was probably one of the first in England to become aware of the work being done by Bunsen and Kirchhoff.  He wrote to George Stokes in February 1860:  "Have you seen in the last no. of the Annales de Chemie et de Physique a short note about Kirchoff's [sic] discovery of the probable cause of the coincidence of the bands of light ... and dark lines of the spectrum?"³⁵  It did not take long for Roscoe to recognize the implications of this research.  Three weeks later, he wrote to Stokes again:  "I hear from Bunsen that he has detected Lithium in all the Potashes he has examined....  He mixed Mg, Ba, Sr, Ca, Li, Na, K salts together, put some of the mixture on the point of a pin -- looked through a telescope & saw at one glance all the substances present!  This is something like Qualitative Analysis!"³⁶

Not everyone in Britain shared Roscoe's enthusiasm.  In the first place, spectroscopy was not an untried investigative method in Britain.  Men still alive and active in 1860, such as David Brewster, Henry Fox Talbot, Charles Wheatstone and William Allen Miller, had made significant contributions to efforts earlier in the century to elevate prismatic analysis beyond empirically based description and speculation to something which had theoretical legitimacy and predictive power.³⁷

Just as celestial mechanicians of the nineteenth century traced their professional ancestry back to Newton's Principia, those who turned the spectroscope to astronomical purposes traced their roots back to his classic paper on the phenomenon of colors.³⁸  Frank James is correct to point out that much of these pioneering spectroscopists' work had been motivated by questions concerning the physical nature of light rather than a desire to produce a sensitive and reliable method of qualitative chemical analysis.³⁹  But the swiftness with which an individual like William Crookes, then editor of Chemical News, sought to construct a British ancestry for the German-born prismatic analysis indicates how closely British spectroscopic investigators identified with the goals of the research agenda opened up by this new method.⁴⁰  It may well be that Kirchhoff received no benefit from earlier work.  But these British investigators saw in Kirchhoff's report something that looked very much like the end they each had had in mind when they designed and performed their own experiments.  They were disgruntled that Kirchhoff had omitted the usual litany of polite acknowledgement of their earlier efforts in his paper.

Also, Kirchhoff touted his discovery as offering a physical explanation for the mysterious Fraunhofer lines.⁴¹  That he observed the behavior he described was not disputed, but questions were raised concerning his ability to claim he had determined a physical cause for the appearance of the Fraunhofer lines.⁴²  Some wondered if the so-called fixed lines were caused by absorption of sunlight by the earth's atmosphere.  Others complained that insufficient study had been made of the spectra of known terrestrial elements to draw any sensible conclusions from an examination of solar absorption lines. ⁴³

In spite of these difficulties, the absorptive and emissive behavior observed by Kirchhoff in the spectra of luminous gases seemed to many individuals so neat, so law-like, that they were willing to accept empirical evidence strongly suggestive of a physical connection between the spectra of metals and the Fraunhofer lines in the solar spectrum in lieu of an explanation.  In addition, Bunsen's discovery of two new elements, cesium and rubidium, in 1860, shortly after beginning work on flame spectra⁴⁴ and William Crookes' discovery of thallium in 1861, significantly heightened interest among chemists in the method.⁴⁵

The hue and cry about the validity of Kirchhoff's explanation for the Fraunhofer lines in popular lectures and journal articles, coupled with Henry Roscoe's enthusiastic proselytizing, kept Kirchhoff's theory before the public eye in Britain long enough to be assimilated into a wider investigative context.  In June 1861, for example, Roscoe addressed the Chemical Society on methods of extending the utility of spectrum analysis in the laboratory.⁴⁶  Roscoe's paper generated considerable discussion reflective of the uncertainty in the audience over the implications of Kirchhoff's work.  On the one hand, John Herschel asked for a clarification of the process by which the dark lines are produced, as, he said, "it has always been difficult for me to understand the usual explanation."  This query was seconded by Michael Faraday.  "It has always seemed to me a very difficult thing," said Faraday, "to see how of necessity there was a depression of the light instead of an increase and exaltation of it."⁴⁷  It rapidly became apparent that none of the distinguished scientists present, including Roscoe, had a firm grasp of Kirchhoff's arguments about the physical process at work, in spite of the fact that Kirchhoff had only two months earlier communicated to the Philosophical Magazine through Roscoe a new and more carefully thought out discussion of what he believed to be the principle behind the dark lines.⁴⁸

On the other hand, it was difficult for some who heard Roscoe's talk to remain unmoved by his crusading fervor on behalf of Kirchhoff's method and theory.  A sense of the positive impact Roscoe's address had on these individuals is conveyed in the remarks of the discussion moderator, Warren De La Rue:

The physicist and the chemist have brought before us a means of analysis that, as Dr. Faraday recently said, if we were to go to the sun, and to bring away some portions of it and analyze them in our laboratories, we could not examine them more accurately than we can by this new mode of spectrum analysis....  Only conceive what refinement of analysis and methods of investigation we have now at our command.⁴⁹

What really excited De La Rue was the potential this method of analysis portended for astronomy:

It is not an uncommon thing for the physicist to tread upon the ground which a chemist thinks belongs to him, and for the chemist to tread upon the ground of the physicist.  Now, we have the chemist occupying the ground of the astronomer, and if the astronomer wants to know something of the constituents of the heavenly bodies, he must come to the chemist.⁵⁰

Warren De La Rue had earned a distinguished reputation among his colleagues in the Royal Astronomical Society for having obtained photographs of the sun and the moon "sufficiently delicate in their detail to advance our knowledge regarding the physical characters of those bodies."⁵¹  Where Agnes Clerke saw, with the advantage of hindsight, astronomical physics as an entirely new kind of astronomy, De La Rue envisioned it as an amalgam emblematic of the emergence of an era of cooperation among physical scientists linked by the spectroscope.  Even though the objects of their research might differ, chemists, physicists and astronomers could be united in their method of investigation.

NOTES
[click on footnote number to return to text]

• Preface

• Introduction

• Chapter 1—

• Chapter 2—

• Part 1—

The Astronomical Agenda:  1830-1870

• Part 2—

"A sudden impulse..."

• Part 3—

Reception of Spectrum Analysis Applied to the Stars

• Chapter 3—

• Part 1—

Cultivating Advantageous Alliances; Opportunism and Eclecticism

• Part 2—

Opportunism and Eclecticism (continued)

• Part 3—

Achieving "A mark of approval and confidence"

• Chapter 4—

• Part 1—

The Solitary Observer

• Part 2—

Celestial Photography

• Chapter 5—

• Chapter 6—

• Part 1—

The Red Flames

• Part 2—

The Eclipse Expedition to Oran

• Part 3—

Photographing the Corona Without an Eclipse

• Part 4—

The Bakerian Lecture

• Conclusion

• Note on Sources

• Published Papers of William Huggins

• Bibliography

• Vita