Department of History
University of California, Irvine
Instructor: Dr. Barbara J. Becker
Week 7. The New Astronomy
"Dispelling the Myth of the Able Assistant:
Margaret and William Huggins at Work in the Tulse Hill Observatory" (1992)
by Barbara J. Becker
a version of this paper appeared in Creative Couples in Science (1996)
Helena Pycior, Nancy Slack, and Pnina Abir-Am, eds.
No doubt you know about my Pension. £100 a year has been granted me, "for my services to Science by collaborating with" my Dearest. This I could accept without any reflection on the memory of my Dearest -- & with honour to myself as well as to him. I do regard the Pension as an honour to him though it is honourable also to me, & I humbly hope,--really earned for the 35 years of very hard work. None of you know how hard we worked here just our two unaided selves.
Accounts of the work of William Huggins always mention that he was assisted in his research by his wife. In A Sketch of the Life of Sir William Huggins, for example, Mills and Brooke explain that "William Huggins did not allow his marriage to interfere with his work," rather that he "derived great benefit from his wife's able assistance." They cite Margaret's own enumeration of her contributions to the work of the Tulse Hill observatory which, in addition to observation, included such things as arranging instruments, working batteries, mixing chemicals, dusting and washing up the laboratory, doing "small things," and being "generally handy." From the description given, the reader is led to understand that while these tasks provided essential support to the work at hand, they were nonetheless subordinate to the research agenda designed and directed by William Huggins.
I will present a new and different interpretation of the collaborative work of William and Margaret Huggins. This new view has emerged as a result of an examination both of their notebooks, which are held at the Whitin Observatory at Wellesley College, and of their extensive correspondence. These documents provide a vivid description of daily activity in the Hugginses' laboratory and observatory, and make possible, for the first time, a more definitive assessment of Margaret Huggins' role in the work at Tulse Hill. An analysis of these documents has revealed the complexity of Margaret Huggins and the influence of her observational, interpretive, and supportive contributions. I shall argue that Margaret Huggins was more than an able assistant, amanuensis, and illustrator, whose work conformed to her husband's research interests: her very presence and expertise not only strengthened but also shaped the research agenda of the Tulse Hill Observatory.
For a number of reasons it has been difficult until now to assess properly the degree of collaborative effort that Margaret's assistance made possible in the Hugginses' work. First, the historical figure of William Huggins, crafted in part by Margaret Huggins herself, has loomed large in retrospectives on the origins of what came to be known as astrophysics. This image is reflected in the classic photograph placed prominently opposite the title page of The Scientific Papers of Sir William Huggins. Here we see the solitary stellar explorer seated alongside his star-spectroscope in his private observatory free of the distracting bureaucratic entanglements as well as the debilitating methodological and theoretical restrictions which, in Huggins' view, encumbered institution-bound observers at Greenwich, South Kensington, and Kew.
Second, biographers have based their discussion of Margaret Huggins' contributions to the work of the Tulse Hill observatory on information gleaned from the Hugginses' published scientific papers and reminiscent accounts. Unfortunately, there is an alluring internal consistency in these versions of their collaborative work which has enhanced their authority over the years and blinded researchers in the past to the need to delve beyond the public façade.
A third reason why it has been difficult to assess Margaret's collaborative role stems from our own twentieth-century predisposition to see in the inkblots of the historical record familiar patterns of scientific organization around which to structure our analysis. Today, collaboration in scientific research is far more common than it was a hundred years ago. Members of large research teams are ranked hierarchically by their peers and individual contributions are assessed accordingly. Principal investigators are evaluated on the basis of such things as originality and insight into the theoretical and practical problems encountered in ongoing research; support personnel's success is measured on the basis of how well they tend instruments, follow instructions, and work cooperatively as part of a team. Reliance upon such standards for historical analysis, however, unnaturally constrains discussion of complementary collaborative efforts in the nineteenth century. Such a scheme makes little sense when describing the work of Robert Bunsen and Gustav Kirchhoff, for example, or that of George Liveing and James Dewar--pairs of men with comparable levels of professional training and technical skill. However, when investigative partners are also husband and wife, there is a risk that a hierarchical evaluative structure may appear applicable to their joint scientific work.
This risk is enhanced when the body of published papers contains what appear to be clear signatures of something like today's hierarchical teamwork structure: husband as observer, wife as instrument tender, husband as principal interpreter of data; wife as recorder, husband as analyzer of measurement error, wife as corroborator; and so on. Thus, it may seem fitting to evaluate the husband's work in terms of its originality and theoretical insight, and the wife's contributions in terms of the peripheral support they supply the research effort.
Recently, Marilyn Bailey Ogilvie has compared the collaborative dynamics of three scientific couples, including William and Margaret Huggins. Ogilvie points out that because the Hugginses' joint published papers are written principally in William's voice, reliance on these documents alone to determine how the work, particularly that done in the midst of active observation, was divided between them, yields a limited picture of Margaret's contributions. Because of this, Ogilvie suggests that a more accurate assessment of the scientific merit of Margaret Huggins' contributions to the work done at Tulse Hill will require an examination of relevant primary material. It is Ogilvie's hope that such an examination will make it possible to contrast Margaret's scientific "originality" against her abilities as data collector and supportive team member.
Ogilvie is right to suggest an historical analysis of the primary sources which underlie the Hugginses' published papers. But, even a cursory glance at the notebooks reveals that Margaret and William did not work together as principal and secondary researchers; rather, they worked as complementary collaborative investigative partners. The constant give-and-take on which such a work relationship is based blurs the usual markers which distinguish an idea or plan's originator from its executor. Thus, I would argue that "originality" fails, in this case, to function as a useful indicator of either William or Margaret's worth as a scientific investigator.
There is, however, an alternative dimension of their collaborative work which presents itself as an insightful evaluative tool, namely that of "individual initiative." A careful reading of the notebooks has uncovered evidence of Margaret's initiative in such diverse activities as problem selection, instrument design, methodological approach, and data interpretation, thus providing a clearer sense of the nature, extent, and value of Margaret Huggins' scientific contributions to the work done at Tulse Hill. This approach, I believe, will prove useful in exploring the working relationship of other collaborative scientific couples.
MARGARET HUGGINS was born in Dublin in 1848. She was the second child and elder daughter of one John Murray, a solicitor, and his wife the former Helen Lindsay. She lived with her family in a Georgian townhouse overlooking the sea at 23 Longford Terrace in Kingstown (now Dun Laoghaire), Ireland. Margaret was about eight years old when her mother died. The information in obituaries and memorial essays written by her friends can be assembled to construct a plausible, but apocryphal, story of her childhood. These sources suggest that Margaret spent a good deal of time with her grandfather, and that she attended private school in Brighton.
Margaret's enthusiasm for astronomical research marvelled those acquainted with her. After her death, her friends' reminiscent memorial essays drew on childhood anecdotes, many no doubt related to them personally by Margaret herself, to speculate on the extraordinary circumstances which may have predisposed her to engage in this unique vocation. Some attributed her early astronomical training to her grandfather, others to her reading an article on spectroscopy in a young people's magazine. A number even suggested that the author of this magazine article was none other than William Huggins himself. A typical example is the obituary written for Science by Sarah Frances Whiting:
Before [Margaret Huggins] reached her teens she worked with a little telescope making drawings of the constellations and sunspots. Later, inspired by anonymous articles in the magazine, Good Words, she became interested in the spectrum, and made a little spectroscope for herself by which she detected the F[r]aunhofer lines. It was the romance of her life that she afterwards became the wife of the astronomer who wrote the papers, and with him made many discoveries with the magic instrument.Some version of this story is repeated with authority in a variety of widely read sources. However, a search through the volumes of Good Words published between 1860, the year the magazine was first published and 1875, the year of Margaret's marriage, has uncovered only one series of anonymous articles on astronomy. Given the style and content of the articles, and William Huggins' own eclectic research interests at the time, it is unlikely that he was their author.
Articles on a variety of astronomical subjects written by such prominent astronomers of the day as Richard Proctor and Charles Pritchard appeared in the magazine during Margaret's youth. Margaret's awareness of and interest in the work of contemporary astronomers undoubtedly resulted from a combined influence of several of these articles read over an extended period of time. However, there is one article by Charles Pritchard, then President of the Royal Astronomical Society, which is worth noting. This article, "A True Story of the Atmosphere of a World on Fire," appeared in the April 1867 number. The "world on fire" Pritchard described was a recently discovered nova. After recounting the flurry of interest this object generated throughout the international community of astronomers, Pritchard introduced W. A. Miller and "Mr. Huggins" of the Tulse Hill Observatory. According to Pritchard, these gentlemen were experts in spectroscopy, and thus able to analyze the nature of such an unusual star.
Pritchard's use of such kinetic phrases as "sudden bound," "strong impulse in a new direction," "aspires to a loftier aim," and "no longer...restricted" conveyed the advantages he felt spectroscopy brought to astronomical research. He provided simple directions for constructing and using a spectroscope complete with suggestions to guide the reader's expectations and insure successful observations. If Margaret's interest in astronomical spectroscopy was indeed piqued by reading one particular article in Good Words, Pritchard's is a likely candidate.
MARGARET AND WILLIAM HUGGINS were married on September 8, 1875 at the Monkstown Parish Church near Margaret's family home. She was about 27 years old and he was 51. One account of their first meeting claims that the pair were introduced by Howard Grubb, William's Dublin-based instrument maker. A more romantic version tells how "the two star-gazers stopped their investigations long enough to 'exchange eyes'...." No documents have thus far been found to substantiate these stories. This is unfortunate because the question of how they met is of historical interest in the context of collaborative couples.
It would also be helpful to be able to trace the sequence of events that sparked William's willingness to work full-time with a collaborator. The few things known with certainty about the early life of William Huggins portend a solitary lifestyle. Born in 1824, William was the sole surviving child of a London silk mercer and his wife. While accounts of his boyhood vary, they all agree that William received little formal education aside from some private tutoring at home. When he reached university age, he remained at home and worked as an assistant in his father's shop. Huggins' scientific activities during this period, while not specifically identified, are nevertheless described as self-motivated and directed--activities, pursued independently in his spare time, which provided him with opportunities for "thinking out problems for himself."
The notebooks reveal that William invited others to his observatory at his convenience. With the exception of his work in the early 1860s with William Allen Miller, Huggins was principally a lone observer until his marriage in 1875. There are few clues to the circumstances which urged him to reconsider this position a few years later and begin full-time collaborative work. Margaret's presence changed both the kind of work done at Tulse Hill and its organization. William's terse notebook jottings were replaced by Margaret's lengthy and detailed entries. More importantly, photography suddenly appeared as a new method of recording what had previously been purely visual spectroscopic observations. Evidence gleaned from the notebooks points to Margaret Huggins as a strong impetus behind the establishment of Huggins' successful program of photographic research.
MANY ACCOUNTS credit Margaret with having learned the basic principles of photography at some time in childhood or adolescence. One close friend went so far as to say that Margaret's skills in photography were self-taught and that she mastered them before she made her spectroscope. But, how fashionable was it for a young woman in the 1860s to be handling smelly photographic chemicals, or lugging around cumbersome tripods, developing boxes, and other photographic equipment? Recently, Bernard and Pauline Heathcote surveyed the establishment of photographic portrait studios in Britain in the mid-nineteenth century. Of the 750 individuals engaged in portrait photography between 1841 and 1855, 22 were women. The number of women who achieved some degree of renown for their work during the early history of photography was small, but not inconsequential. Queen Victoria was an early patron of the Photographic Society of London. This royal enthusiasm for photography may have encouraged women with both the leisure and the financial means to experiment with the emerging art form.
Margaret's interest in photography identifies her as one of an adventurous group of young women of her day. The Reverend Edward Bradley, writing under the penname of Cuthbert Bede, advertised photography as the ideal entree for a young lady into the science of chemistry. Remarkable effects could be produced with little or no understanding of basic chemical principles. At the same time, it was socially acceptable for such activity to form the basis of polite, if somewhat "mystical" ballroom conversation. Bradley cautioned his readers that experimentation with photography had its inherent risks. He illustrated this with a humorous engraving which depicted one mother's anxious visit to the chemist's shop after a photographic mishap left black chemical stains on her daughter's face. In the caption, the mother explained to Mr. Squills, the chemist:
I cannot persuade [my daughter] to be sufficiently careful with her photographic chemicals and she has had a misfortune with her nitrate of silver. Unless you can do something for her, she will not be fit to be seen at Lady Mayfair's to-night.Photographic work at that time was a complex and often frustrating activity even for those with experience and considerable skill. In fact, until the 1880s when ready-made photographic plates became widely available, few were prepared to invest the time, money, and energy required to make photography an avocation. William Huggins' early photographic experience seems to have been limited to producing some lunar photographs in the late 1850s. While the facts behind Margaret's training in photography remain unclear, there is sufficient evidence available in the laboratory notebooks to demonstrate that her practical and technical photographic expertise was considerable by early 1876, when she assumed the task of making the notebook entries.
The first paper devoted solely to spectral photography done at Tulse Hill appeared in the Proceedings of the Royal Society in December 1876, with William Huggins as the author. For purposes of priority, Huggins prefaced the paper with the statement: "In the year 1863 Dr. Miller and myself obtained the photograph of the spectrum of Sirius." William Allen Miller, Huggins' neighbor and friend, taught chemistry at King's College in London. Miller was an old hand at spectroscopy and a skilled photographer. In fact, Miller's expertise meshed well with Huggins' astronomical skills as they joined forces to examine the spectra of celestial bodies in 1863. During the course of this investigation, Huggins and Miller twice captured an image of Sirius' spectrum on a wet collodion plate as they reported in a preliminary notice published in the Royal Society's Proceedings of 1864, while a fuller account appeared in the Philosophical Transactions of that same year.
Huggins wished the readers of the paper of 1876 to view his newer photographic work on star spectra as a resumption of his earlier work with Miller. To establish this connection, Huggins excerpted a paragraph from the paper of 1864, which concluded with the statement, "Our other investigations have hitherto prevented us from continuing these experiments further; but we have not abandoned our intention of pursuing them." This said, the paper of 1876 continued, "I have recently resumed these experiments...." Thus, William Huggins neatly compressed the intervening years into a moment's hesitation.
Huggins' papers on photographing stellar spectra in the Philosophical Transactions and Proceedings of 1864, contain the only extant record of his photographic work before 1876, as yet uncovered. There is no mention of this work or any other photographic experiments anywhere in the sections of the observatory notebooks which date from the early '60s. Perhaps Miller took the notes. Perhaps the photographs themselves were viewed at the time as the only necessary record. Perhaps the attempt was seen as such a failure that it did not warrant more than a passing comment. Perhaps there is a missing notebook. The fact that no record has been found which can provide any detail concerning Huggins' early photographic work is indeed problematic. It seems clear that, in spite of their intentions to the contrary, Huggins and Miller did not pursue their photographic experiments on stellar spectra.
Huggins' spectroscopic work on nebulae and the motion of stars in the line of sight was done at a time when rapid improvements were being made in photographic processes. Nevertheless, he pursued this taxing research using only visual observations. What held him back? In the paper of 1876, Huggins explained, "Considerable delay [in resuming photographic work] has arisen from the necessity ... of a more uniform motion of the driving-clock." Twenty years later, in 1897, Huggins reminisced that he and Miller "did not persevere in our attempts to photograph the stellar spectra" because the available photographic methods were unsuitable for such work. Wet collodion processes, he claimed, were inconvenient and dry plates were not sensitive enough. Both of these explanations, coming as they did many years after the fact, distilled the difficulties which Miller and Huggins faced in their early photographic efforts into an acceptable formulation for contemporary consumption. That Huggins bothered to give any explanation for his lack of use of photography during this period demonstrates his awareness that some excuse was necessary. One cannot help but wonder if Huggins had sufficient skill or interest in photography to continue such work independently.
Following their marriage in 1875, William and Margaret began a rigorous program of photographic experiments. March 31, 1876 marks Margaret's first entry in the notebooks. She wrote:
Photographed Sirius. Wet Plate, 9 minutes exposure. Photograph on the edge of the plate in consequence of want of adjustment. 3 lines across refrangible end of spectrum.The next entry, on April 3, states:
Took a photograph of Venus with a wet plate and 8 m. exposure.... Afterwards tried to photograph Betelgeuse with a Dry plate and exposure of 30 m. No image[,] which may be accounted for by the sky being overspread with thin white haze.
Nearly every entry thereafter contains some mention of photographic work. The process employed at the start was wet collodion, although the entry for May 7 notes a comparison of the wet and dry process. Margaret reported:
The dry plate gave best results.... These results were so good that thought I might endeavour to photograph the spectrum of Venus using the same narrow slit I had from the Solar Spectrum.Here we see her first use of the first person, a practice which could be attributed to the fact that she was merely transcribing her husband's personal notes about the work that was done. There is no way to check this independently, and it cannot be ruled out as a possibility. However, by December 1876 Margaret was using the first person plural along with impersonal predicate phrases and sentences in the first person singular. In July 1879 Margaret began to use the initial "W" to single out her husband's contribution to the work at hand, while she referred clearly to her own work in the first person singular.
Margaret's entries soon reveal her interest in experimental design. On May 9, 1876, for example, she wrote that she "took one or two photographs of Solar spectrum with a view to determining how wide I might open the slit and still obtain lines." By June she was demonstrating her expertise in improving and adapting both instruments and methods to the new photographic tasks at hand:
I had a new and much smaller camera made to use in connection with the above described apparatus.... I was occupied upon all favourable days in testing and adjusting this photographic apparatus upon the solar spectrum: at the same time testing different photographic methods with a view to finding, relatively to different parts of the spectrum the most sensitive, and relatively to the whole spectrum the quickest method for star spectra.
Margaret Huggins' design for a new camera.
The entire summer of 1876 seems to have been devoted to experimentation with different types of light sensitive plates. The last mention of the use of wet collodion was made on August 17. After that, only dry or gelatine plates were used. By December 1876, plates--all gelatine--were identified only by their manufacturer.
Margaret also made substantial improvements to the observatory's equipment which moved the Hugginses quickly into the forefront of spectroscopic astrophotography. She was innovative and interested in experiment. On September 19, 1876, Margaret wrote:
Finding it impossible to feel certain whether the apparatus was perfectly axial in the telescope, I had a small brass tube made & placed as marked in the diagram. This tube being furnished with cross wires placed very accurately at right angles: it could be ascertained by observing when the angles of the cross wires coincided whether the apparatus was perfectly axial....As the years went by Margaret continued to take the initiative whenever photography was employed at Tulse Hill. Her interest in problem selection, for example, comes out in a note she added to a letter her husband wrote to David Gill in 1879: "If only a few nights sufficiently clear come," she wrote, "I want to try photographing a nebula. The difficulty would be to keep it on the slit: -- but difficult as it would be I am most eager that we should try & get some result. It would be valuable." By 1887 she was sufficiently confident in her own interpretive skills to note, "I cannot feel sure there is anything on the nebula plate but William fancies there is. Well if there be anything it's practically useless it's so faint." By 1893 she had her own ideas about what counted as a quality photograph and what was required to obtain one:
I was ... unable to be in the Observatory but W[illiam] insisted on working alone. Again tried Messier 15, giving exposure from 6.10 to 9 p.m.... Developed next day and delighted to find a spectrum good enough to tell us something. It is not however as strong as I should have liked & I regret much that W[illiam] would not take my counsel & have left the plate in so that it might have had continued exposure the next fine night.While published articles about the early photographic accomplishments at Tulse Hill make no mention of Margaret Huggins, it is clear from the notebooks that Margaret's photographic skill made possible an important shift in the research agenda at Tulse Hill. William Huggins' notebook entries during the five years preceding his marriage show that, in addition to his visual spectroscopic work, he participated in the ongoing astrometric program guided by Greenwich and the Royal Astronomical Society. Thus, he timed occultations and eclipses, observed visual changes in comets, and drew pictures of planet surfaces. But photography played no role in this enterprise until the year after his marriage.
THROUGHOUT THE 1880s the Hugginses were engaged in two principal efforts: the first involved their attempts to photograph the solar corona without eclipse. The second centered on their interest in examining different nebulae to resolve the nature of what came to be known as the "chief nebular line," a green emission line which William had noted some years earlier in the spectra of several nebulae. This line is located tantalizingly close to, but not precisely coincident with, spectral lines associated with several terrestrial elements. Margaret contributed actively to both of these research projects. Both projects embroiled the Hugginses in controversy over methods, instruments, and interpretation of received data. But, I wish to focus on this second effort, namely that involving the determination of the nature of the principal nebular line, because it was the subject of the first paper on which Margaret Huggins appeared as co-author. As such, it serves as a benchmark in the Hugginses' collaborative relationship.
It is not clear why this particular paper was their first co-authored paper. Given William's awareness of its potential for controversy, he might have introduced Margaret on a gentler slope. In the paper's introduction he explained: "I have added the name of Mrs. Huggins to the title of the paper, because she has not only assisted generally in the work, but has repeated independently the delicate observations made by eye." These "delicate observations" required making repeated direct visual comparisons of the spectrum generated by burning magnesium in the laboratory against that produced by a nebula. The brilliance of the burning magnesium was blinding while the faint light of the nebulae tested the limits of human visual sensitivity. Nevertheless, this "labourious & anxious task," Huggins wrote in a letter to George Stokes, "I and Mrs. Huggins, who is now a very trained observer of such things have done to the utmost of our ability, and with the greatest possible care."
Their first joint paper is written principally in the first person singular. The first person plural is used less than twenty times in twenty pages, and nearly half of the time it connotes a more general usage. Margaret is referred to twice by name when her independent corroborations of William's observations are noted. However, it should be pointed out that no specific statement is made concerning the nature or quality of these confirmatory observations even though the paper cites the details of corroborating evidence supplied by several other astronomers. Even more important, no attention is ever drawn to her methodological or interpretive contributions. It is well to keep in mind that it had been twenty-five years since William last co-authored a paper. Changing one's accustomed mode of expression takes time, and subsequent papers co-authored by the Hugginses do show an increased use of the first person plural. But, certainly, the reader of this first co-authored paper who was unfamiliar with the degree of Margaret's involvement in the research effort would have had no reason to assume her role to have been anything more than titular. A comparison of the notebook records with the presentation of this same research in the published paper brings to light Margaret's role in this particular research effort. It also provides some clues as to why this work and not some other was chosen as their first joint publication.
The Hugginses' work on this project began in the fall of 1888. On October 12 Margaret described their plans to begin work comparing the spectrum of magnesium with that of a nebula:
I go back a day now to say a word about what we have been very busy about all this week. We are very anxious to try and determine whether the Mg line which Lockyer asserts is coincident with the 1st Nebula line, and the Mg line which he also asserts to be coincident with our new Nebula line, -- really are so coincident. To try and throw light on this very important point -- for much may turn on it -- we wish to examine by eye various nebulae for the 1st line, with the 15" and compare directly with the nebula line the spectrum of Mg.J. Norman Lockyer, editor of Nature, professor of astronomy at the Normal School of Science (later the Royal College of Science) at South Kensington, and member of the Committee on Solar Physics, was by this time an arch-rival of William Huggins. The clash of their personal styles coupled with the similarity of their research interests had long since placed them on a collision course. The issue of the identity of the chief nebular line provided one more opportunity for them to meet head-on.
Lockyer contended that all celestial bodies were comprised of swarms of meteors in various stages of evolutionary development. In Lockyer's view, the heat generated by collisions of large numbers of meteors in space made them incandescent. Varying numbers and intensities of these collisions were responsible for the individual differences observed in the population of known nebulae. Lockyer was encouraged in this view by his observation that when magnesium, an element common to meteors, was brought to a sufficiently high temperature, a line appeared in its spectral signature which was virtually coincident with that of the chief nebular line.
Illustration by Lockyer showing the probable presence of magnesium in the light of comets, meteors, and nebulae.
William Huggins, on the other hand, considered the nebulae to be gaseous. When Huggins first observed the chief nebular line in 1864, he suggested that its proximity to a known line of nitrogen indicated the possibility that nebulae contained some exotic form of that element. Subsequent observation dissuaded him of this view, however, and by 1889, he and Margaret were of the opinion that nebulae might be composed of some new, and as yet undiscovered material. Hence, they were inclined to argue that the nebular line, while very close, was distinct from that of any associated with magnesium.
Illustration by William and Margaret Huggins showing that nebulae do not exhibit the same spectrum as magnesium.
In order to gather conclusive evidence in support of their view, the Hugginses set out to make a direct comparison of several nebular spectra against that of burning magnesium. To do this satisfactorily required the spectrum observed through their telescope to be perfectly aligned with that of the comparison apparatus. This alignment was achieved by making use of the magnesium b band, the closely spaced series of Fraunhofer lines in the green part of the solar spectrum. Thus, the bright emission lines in the b band of the laboratory spectrum were matched up with the dark absorption lines of the daytime sky. This calibration was of critical importance and much care was taken in its execution. As Margaret explained:
It has taken much trouble to get everything satisfactorily arranged.... First, we directed the telescope & spectroscope to the sky.... Then Mg was flashed in as required. We did not leave the apparatus until we both felt satisfied that coincidence between the dark b [band] of daylight & the bright b [band] of the burning Mg was perfect.... We considered the apparatus as now ready for use.Throughout the fall and winter the Hugginses directed their attention to the problem of the nebular line comparison. In February 1889 William began keeping a separate record of his own observations in an old notebook. The occasional overlap in their notebook entries during this period provides sparse but valuable insight into their individual research interests, methods, and concerns. On March 6 after a number of visual observations and one attempt to secure a photograph of the nebular spectrum in direct comparison with that of burning magnesium, William drew a sketch of what he had observed. With the crosswire centered on the magnesium line, the chief nebular line appeared to him to be just a bit to the left, or more refrangible side of the magnesium line. In Margaret's March 6 entry, she mentioned that they were thinking of sending a paper to the Royal Society about their work. To that end, she recorded that on March 9, they rechecked the calibration of their apparatus.
W[illiam] then put the spectroscope on the Moon bringing in the b group so that I might observe whether the Mg lines coincided exactly with those of the b group. I thought not decidedly....William's March 9 entry makes no mention of the recalibration, but rather concentrates again on confirming his previous observation of the placement of the nebular line in comparison with that of magnesium. Two days later, Margaret wrote that the calibration was checked once again:
W[illiam] thought the bright line did fall coincident. Then I observed. I found a difficulty in getting good observations. A number, did rather give me the impression that it was after all coincident: but one thoroughly good observation showed me as distinctly as I saw it on Saturday night that the bright line was not truly coincident but on one side. I left off feeling certain on the point.In spite of the care they had taken earlier in calibrating their instruments, the telescopic spectrum was now observed to be no longer coincident with that of the comparison apparatus. Margaret observed this lack of coincidence and, although William was initially unable to confirm her observation, she felt "certain" of it. William apparently became convinced of the alignment problem on the night of March 11, and remarked casually in his notebook entry that "this state of adjustment is satisfactory for comparison of nebulae, and can be allowed for."
While William may not have been aware of it at the time, Margaret's discovery of the lack of alignment in the comparison apparatus averted what would have been for him an unspeakable calamity. William's constant references in his published papers to the care and accuracy of his observations were underscored by his use of four significant digits in reporting his results. If the reliability of his data was ever brought into question, it not only would have meant the loss of the debate with Norman Lockyer on the question of the chief nebular line but it also would have damaged his credibility in the wider community of astronomers.
By the time the misalignment was recognized, the season for observing the Orion Nebula was coming to an end. There was no time to recalibrate the instruments and take chances on the weather providing enough clear nights to make a second set of observations. Besides, their only successful photograph had been taken just a week before the misalignment was discovered. Difficulties in getting good photographs of the nebular spectrum had already persuaded them to abandon further photographic attempts for the moment and concentrate their energies on visual comparisons. Still, the importance of having some photographic evidence to support their visual observations was uppermost in the Hugginses' minds. Thus, based on Margaret's confidence that their spectroscope was "not shifty," and, hence, that the observed disparity was constant over all their observations, the paper came to be written based on data acquired when the instruments were ever-so-slightly out of alignment.
The separation between the nebular line and that attributed to magnesium was clearly small. In spite of the slight displacement of their equipment which reduced the separation of these lines even more, both Margaret and William were confident they each had observed it. This, Margaret believed, added even greater strength to their argument. She noted:
Now this observation is important for it showed that our arrangements really displaced the Mg line slightly to the left towards the neb. line, thus making it more difficult to observe the doubleness by reducing the true separation between the neb. line & the Mg oxide one.... This observation that our Mg lines are displaced slightly towards the left, surely gives great force to our observations showing duplicity....In their paper on the spectrum of the Great Nebula in Orion, the Hugginses artfully converted this potentially disastrous turn of events into a forceful argument in favor of their view on the nebular line. They perfunctorily declared the serendipitous misalignment to be a purposeful one--an experimental design chosen to give their opponents every conceivable advantage:
Indeed, to prevent any possible error in the observation of apparent want of coincidence of the nebular line ... the arrangement was purposely made that the lines of magnesium were seen to fall ... a very little on the more refrangible side of the middle of those lines ... if under such circumstances, the nebular line was seen on the more refrangible side of that of magnesium the observation would be much more trustworthy....Was it Margaret's suggestion to transform this accident into a conscious instrumental adjustment? Did this maneuver win her co-authorship? Undoubtedly it played an important role. But it should be pointed out that the observations being made were exhausting ones. Margaret frequently complained that the dazzling light of the burning magnesium tired her eyes. She felt this made her observations less reliable. Margaret would have been about 40 at this time while William was 65. Were his eyes so resilient that these observations could have been managed without a collaborator? This kind of work made teamwork essential. While William may have been able to overlook Margaret's earlier contributions, these efforts would have been harder to ignore.
All these practical considerations provide an array of positive factors which may have urged William to include Margaret as co-author of this paper. Today, it is even tempting to suggest that her co-authorship was the consequence of her husband's pioneering support of women engaged in scientific work. Nevertheless, William's motives for adding Margaret's name to this particular paper may not have been wholly altruistic. There is another factor which needs to be considered, and that is the Hugginses' interest in preserving and perpetuating William's image as an observer whose extreme care and caution urged him to reject interpretational speculation.
In spite of the Hugginses' precautions, the work on the chief nebular line had presented both Margaret and William with tremendous difficulty. It was conceivable that their observations might not be confirmed by others in future trials. Some unforeseen circumstance could force them to modify or even retract their claims. Such a concern would have been much on William Huggins' mind as he contemplated sending the Orion Nebula paper to the Royal Society in March 1889. Just a few months earlier Lockyer, as part of his effort to find additional observational support for his meteoritic hypothesis, reviewed the existing literature on cometary spectra. This led him to question the accuracy of a diagram William Huggins had included in a paper written a number of years earlier on Comet b, 1881. It turns out that Margaret had drawn the diagram. William wrote to George Stokes:
The diagram was drawn by Mrs. Huggins & there is a slight error in the relative strength of H & K, but the diagram was not intended to be a picture of the solar spectrum, but simply to show the relative positions of the solar lines & the new lines.Margaret, meanwhile, added the following comment to her original notebook entry made in June 1881:
In making the diagram I was in consultation with my husband. The measures upon which the diagram was laid down were made for the most part by both of us one checking the other and were many times repeated.... But no matter how much care is taken in a matter of this sort, accuracy can only be approximate. The characters and intensities of the lines and groups are I think fairly truthfully represented--but the number of the lines given in the faint group between H and h is only a guess.... But while acknowledging these guesses, I wish to state that they are not guesses at haphazard, but are guesses founded upon careful examination of our comet plates compared with others concerning the interpretation of which there can be no doubt.Which is the more convincing statement? Clearly William needed Margaret at this particular moment to help shoulder the burden of proof should Lockyer eventually turn up some damning evidence to counter their nebular line work.
Piecing together the available historical record in order to better interpret an individual's actions in a given situation some hundred years after the fact is the historian's challenge. Fortunately sufficient documentation survives to permit an enumeration of some of the factors which may have encouraged William to include Margaret as co-author of this particular paper. Certainly it seemed to require extraordinary circumstances to draw his attention to the value of her contributions to the research they did together. In this instance, an array of extraordinary factors came together to push William over the conventional brink.
WILLIAM AND MARGARET HUGGINS lived and worked together for thirty-five years as complementary collaborative investigative partners. This new interpretation of their working relationship differs from that which has been drawn from the published record and reminiscent accounts. Given the rich store of extant primary source material providing insight into their lives and work, why has the full extent of their collaboration only recently come to light? Why has the image of William as the principal investigator and Margaret as his able, but subordinate, assistant persisted for so many years? It may be argued that the correspondence is too widely scattered, or that the notebooks are not readily accessible to the historian wishing to examine these documents in tandem with the more visible and available published record. These are indeed serious obstacles. But, there is a more formidable barrier which must be overcome, and that is the power of the Hugginses' historical image itself.
The traditional and romanticized image of the Hugginses' collaborative efforts is largely their own creation. It has endured because it has been verified and amplified by the published accounts, and because it has fitted the needs and expectations of those who have retold the tale. William and Margaret worked hard to present themselves as classic representations of Ruskin's ideal Victorian couple:
[The man] is eminently the doer, the creator, the discoverer, the defender. His intellect is for speculation and invention.... But the woman's ... intellect is not for invention or creation, but for sweet ordering, arrangement, and decisions.
The strength of this legendary image is captured in the photograph of William seated alone beside his star spectroscope. The absence of Margaret is telling. If we now turn back for a moment to Margaret's impassioned statement to Larmor, that "None of you know how hard we worked here just our two unaided selves," we catch her in a rare moment of candor which offers us a brief glimpse of the truth.
 Agnes M. Clerke, A Popular History of Astronomy during the Nineteenth Century (Edinburgh, 1887), 421.
 Margaret Lindsay Huggins to Joseph Larmor, October 17, 1910, Lm. 790, Larmor Papers, Royal Society of London Library, London.
 See, for example, William Huggins, "The New Astronomy: A Personal Retrospect," The Nineteenth Century XLI (June 1897): 907-929, 926; Charles E. Mills and C. F. Brooke, A Sketch of the Life of Sir William Huggins (London, 1936), 37-42; E. W. Maunder, Sir William Huggins and Spectroscopic Astronomy (Sidcup, 1980), 64; Marilyn Bailey Ogilvie, "Marital Collaboration: An Approach to Science," in Uneasy Careers and Intimate Lives: Women in Science 1789 - 1979, Pnina G. Abir-Am and Dorinda Outram, eds. (New Brunswick NJ, 1987), 104-125; 111-115.
 Mills and Brooke, Sketch, 38-41.
 Observatory Notebooks of William and Margaret Huggins, Whitin Observatory Library, Wellesley College, Wellesley MA. There are six known observatory notebooks. For published descriptions of their contents, see Sarah Frances Whiting, "The Tulse Hill Observatory Diaries," Popular Astronomy 25 (1917): 158-163; and Julie Morgan, "The Huggins Archives at Wellesley College," Journal for the History of Astronomy 11 (1980): 147. In this paper, I will refer to the notebooks by the numbers given them in these accounts.
 There is no one repository for Huggins' correspondence. Principal collections can be found in the Cambridge University Library Archives, Cambridge, England: correspondence with Sir George Stokes, the Reverend Thomas Romney Robinson, Sir George Airy among others; the Royal Astronomical Society Archives and the Royal Society Library, London: correspondence with John Herschel, Arthur Schuster, Joseph Larmor among others; Museum of American History, Smithsonian Institution, Washington, D.C.: microfilm of correspondence with George Ellery Hale; Mary Lea Shane Archives of the Lick Observatory, University of California, Santa Cruz CA: correspondence with E. S. Holden, J. Keeler, W. W. Campbell among others; Pusey Library, Harvard University, Cambridge MA: correspondence with E. C. Pickering; Dartmouth College Library, Hanover NH: correspondence with C. A. Young; Library of Congress, Washington, D.C.: correspondence with Simon Newcomb and T. J. J. See.
 W. Huggins and M. Huggins, The Scientific Papers of Sir William Huggins (London, 1909).
 See, for example, Derek de Solla Price, Little Science, Big Science (New York, 1963), 86-91; Warren O. Hagstrom, The Scientific Community (Carbondale, 1965), 105-58; Alvin M. Weinberg, Reflections on Big Science (Cambridge MA, 1967), 47-53; idem., "Scientific Teams and scientific Laboratories," Daedalus 99 (1970): 1056-1075; Lowell L. Hargens, et al, "Research Areas and Stratification Processes in Science," Social Studies in Science 10 (1980): 55-74.
 Ogilvie, "Marital Collaboration," 109-115.
 Margaret Huggins is listed as being 32 years of age in the 1881 census. 1881 Census Return for 90 Upper Tulse Hill Road, Lambeth, Holy Trinity Ecclesiastical District, RG 11/615/10. I am indebted to Dr. Maire Brück for much of the biographical information about Margaret Huggins' childhood.
 September 9, 1875, Irish Times. I am indebted to Dr. Ian Elliott of the Dunsink Observatory, Dublin, for making this information available to me.
 Personal communication, Dr. Ian Elliott to the author, October 3, 1991.
 Ibid. Margaret's mother, Helen Lindsay, died in January 1857.
 Whiting, "Lady Huggins," Science 51 (1915): 853-855; 854. See also, Whiting, "Margaret Lindsay Huggins," Astrophysical Journal 42 (1915): 1-3; Louise Manning Hodgkins, "Lady Huggins: Astronomer," The Christian Advocate (October 21, 1915): 1417-1418; H. F. Newall, "Dame Margaret Lindsay Huggins," Monthly Notices of the Royal Astronomical Society 76 (1916): 278-282; Ogilvie, "Marital Collaboration," 110.
 Anonymous, "God's Glory in the Heavens," Good Words 1 (1860): 23; 116; 161; 225; 289; 465; 513; 577; 625; 729. This series included: "The Moon, Is It Inhabited?," "The Approaching Total Eclipse of the Sun," "Comets--Their History," and "The Structure of the Planets."
 Reverend Charles Pritchard, "A True Story of the Atmosphere of a World on Fire," Good Words 8 (1867): 249-56.
 Ibid., 250.
 Ibid., 251.
 Marriage Record, September 8, 1875, Monkstown Parish Church, Dublin County.
 Hodgkins, "Lady Huggins," 1417.
 1851 Census Return for 97 Gracechurch St., London, St. Peter-upon-Cornhill Parish, HO 107/1531/1.
 Mills and Brooke, Sketch, 11.
 In a list of Fellows of the Royal Astronomical Society, Huggins was noted as living at "Alpha Cottage, Upper Tulse Hill"; see Memoires of the Royal Astronomical Society 24 (1856): 253. In the 1861 census, the homes in the Hugginses' immediate neighborhood were identified by names rather than numbers; see 1861 Census Return for "Alpha Cottage" and neighboring residences, Lambeth, Holy Trinity Ecclesiastical District, RG 9/364/23. At some point in the 1860s Huggins began to give his address as 90 Upper Tulse Hill Road, and always referred to his observatory as the Tulse Hill Observatory.
W. Huggins, "Description of an Observatory Erected at Upper Tulse Hill," Monthly Notices of the Royal Astronomical Society 16 (1856): 175-176.
 In Notebook 1, for example, Huggins mentions the visit of the Clissold family to observe the moon on October 22, 1858, while Mrs. E. Viney and Annie came to observe Venus on April 16, 1860. Huggins' neighbor and collaborator, W. A. Miller is mentioned only once in this notebook: on June 3, 1862, Miller and his family visited the observatory hoping to see the shadow of Titan cross the bright surface of Saturn--they were disappointed. The second notebook, in which William began recording observations in March 1866, contains a lengthy list of prominent observatory visitors, including a few notables whose visits dated back to 1859 and 1860.
 William Huggins co-authored several papers with W. A. Miller on stellar spectroscopy which were published in both the Proceedings and the Philosophical Transactions. While the principal collaboration on which these papers were based reportedly took place between 1862 and 1864, Huggins' notebook entries reveal that Miller paid occasional visits to Huggins' observatory from 1866 until the time of his death in 1870.
 See, for example, "Lady Margaret Huggins," Who Was Who: 1897-1916 (London, 1935); Alice E. Donkin, "Margaret Lindsay Huggins," The Englishwoman (May, 1915): 152-159; 152.
 Bernard V. and Pauline F. Heathcote, "The Feminine Influence: Aspects of the Role of Women in the Evolution of Photography in the British Isles," History of Photography 12 (1988): 259-273; 260.
 See for example, Julia Margaret Cameron, Victorian Photographs of Famous Men & Fair Women, Tristram Powell, ed. (Boston, 1973). Other prominent women who gained recognition for their photographs include Lady Hawarden, the Countess of Rosse, and Princess Alexandra. See Heathcote and Heathcote, "Feminine Influence," 269. There were also increasing employment opportunities for working class women in photography. See Jabez Hughes, "Photography as an Industrial Occupation for Women," The British Journal of Photography 20 (1873): 222-223.
 C. Bede [Edward Bradley], Photographic Pleasures: Popularly Portrayed with Pen and Pencil, (London, 1855), 49-52.
 Although there is no mention of this activity in the notebooks, Huggins' involvement in lunar photography is briefly alluded to in an address on celestial photography given before the British Association by Warren De la Rue. See, Warren De la Rue, "Report on the Present State of Celestial Photography in England," Report of the British Association (Aberdeen, 1859): 130-153; 132.
 By the time their first co-authored article appeared, William and Margaret had been married for nearly fifteen years. Margaret's active involvement in the daily routine of the observatory during that time raises the natural question of the degree of her participation in the writing and editing of papers submitted for publication. Unfortunately, this cannot be determined with any confidence. However, it should be pointed out that William, as Fellow of the Royal Society, was the one privileged to submit papers. Whether or not he was, in fact, the principal author of papers submitted after 1875, every effort would have been made to insure that it appeared that way. If Margaret participated in this process, she did so knowing that she was effectively writing herself out of the published accounts.
 W. Huggins, "Note on the Photographic Spectra of Stars," Proceedings of the Royal Society 25 (1876): 445-446; 445.
 Clerke, "William Allen Miller," Dictionary of National Biography 37 (1894): 429-430. Miller, "On the Photographic Transparency of Various Bodies, and on the Photographic Effects of Metallic and Other Spectra Obtained by Means of the Electric Spark," Philosophical Transactions 152 (1862): 861-887.
 W. Huggins and Miller, "On the Spectra of Some of the Fixed Stars," Proceedings of the Royal Society 13 (1864): 242-244; 244. Idem, "On the Spectra of Some of the Fixed Stars," Philosophical Transactions 154 (1864): 413-435; 428.
 The wet collodion process was not the only photographic process available in 1863, although it is clearly the one with which Miller was familiar. Since Huggins and Miller were attempting something quite new and untested in applying photography to their infant program of observing stellar spectra, it seems reasonable to assume that Miller's experience with the wet collodion process would have made that the process of choice at that time. But, throughout the 1860s, photographers were mixing things like honey, glycerine, and beer with the collodion to prolong the exposure time available to users of wet plates. They also experimented with ways of increasing the light sensitivity of various types of dry plates. In addition, the gelatine dry plate was introduced in 1871. (See, Beaumont Newhall, The History of Photography from 1839 to the Present Day [New York, 1964], 47-57, 83-95.) Though Huggins continued his observations of motion in the line of sight after that time, and made comparisons of nebular spectra with those of various terrestrial metals, there are no indications in the notebooks that photography was ever attempted.
 W. Huggins, "Note on Photographic Spectra," 446.
 W. Huggins, "New Astronomy," 914; idem, "Presidential Address," Report of the British Association (Cardiff, 1891): 3-37; 31-32. See also, Clerke, "Sir William Huggins," Encyclopedia Britannica, 11th ed, 13: 856-857.
 M. Huggins, March 31, 1876, Notebook 2.
 M. Huggins, April 3, 1876, Notebook 2.
 M. Huggins, May 7, 1876, Notebook 2.
 In the correspondence uncovered thus far, it would appear that Margaret rarely took dictation from William, but when she did, she made this point clear to the reader. On December 6, 1895, for example, Margaret wrote a letter to David Peck Todd which was dictated to her by William. At the end of the letter, she explained, "My husband at present is unable to write owing to a chill having affected his hand neuralgically ... so I am giving myself the pleasure of being his secretary." W. Huggins to David Peck Todd, December 6, 1895, Todd Papers, Manuscripts and Archives, Yale University Library, New Haven CT.
 M. Huggins, July 28, 1876, Notebook 2.
 M. Huggins, May 9, 1876, Notebook 2.
 M. Huggins, "June" 1876, Notebook 2.
 M. Huggins, September 19, 1876, Notebook 2.
 Note added by Margaret Huggins. W. Huggins to David Gill, October 7, 1879, Gill Papers, South African Astronomical Observatory Archives.
 M. Huggins, March 21, 1887, Notebook 2.
 M. Huggins, November 12, 1893, Notebook 5.
 W. Huggins, "On the Spectra of Some of the Nebulae," Philosophical Transactions 154 (1864): 437-44.
 See, for example, Ogilvie, "Marital Collaboration," 111-114.
 There is no way to know with confidence if William's adding Margaret's name to this paper was an action taken on his own initiative or if it resulted from her insistence on recognition for her contributions. Thus, I have used the word "introduce" here in a very literal sense, to refer to the fact that Margaret's inclusion in the title of this paper was made possible by William's fellowship in the Royal Society.
 W. Huggins and Mrs. Huggins, "On the Spectrum, Visible and Photographic, of the Great Nebula in Orion," Proceedings of the Royal Society 46 (1889): 40-60; 40.
 W. Huggins to Stokes, April 27, 1889, Stokes Papers, Add MS 7656.H1243, Manuscripts Room, Cambridge University Library, Cambridge, England.
 I have examined the notebook entries made by Margaret and William Huggins from October 1888 through April 1889 when the research for their paper on the spectrum of the Orion Nebula was being done.
 M. Huggins, October 12, 1888, Notebook 2.
 J. Norman Lockyer, "Researches on the Spectra of Meteorites. A Report to the Solar Physics Committee," Proceedings of the Royal Society 43 (1887): 133-139; idem, "Suggestions on the Classification of the various Species of Heavenly Bodies," Bakerian Lecture, Proceedings of the Royal Society 44 (1888): 2-4. For a discussion of the broader issues involved in the controversy between Lockyer and Huggins over the identity of this spectral line, see A. J. Meadows, Science and Controversy: A Biography of Sir Norman Lockyer (Cambridge MA, 1972), chapter 7, especially 183-187.
 W. Huggins, "Spectra of Nebulae," 444.
 This new element was referred to by a variety of names, of which "nebulium," apparently coined by Agnes Clerke, became popular. William Huggins called it nebulum, while Margaret suggested nephelium or nephium in order to keep in line with the Greek nomenclature used in naming helium and argon. See M. Huggins, "...Teach Me How to Name the ... Light," Astrophysical Journal 8 (1898): 54; Richard F. Hirsh, "The Riddle of the Gaseous Nebulae," Isis 70 (1970): 197-212; 203.
 M. Huggins, October 12, 1888, Notebook 2.
 W. Huggins, February 18, 1889, Notebook 3.
 W. Huggins, March 6, 1889, Notebook 3.
 M. Huggins, March 9, 1889, Notebook 2.
 W. Huggins, March 9, 1889, Notebook 3.
 M. Huggins, March 11, 1889, Notebook 1.
 W. Huggins, March 11, 1889, Notebook 3. Unfortunately, Margaret stopped making her separate notebook entries at this point and did not resume them until September 1889, although William continued his entries with some regularity into May of the following year. These entries provide additional opportunities to explore the Hugginses' collaborative relationship as the controversy over their nebular line work intensified. This will be discussed in my dissertation.
 This would become clearer to them in the year following the appearance of their paper as Lockyer raised the issue of what he viewed as William Huggins' excessive claims to measurement accuracy. See Lockyer, "On the Chief Line in the Spectrum of the Nebulae," Proceedings of the Royal Society 48 (1890): 167-198.
 See M. Huggins, March 6, 1889, Notebook 2.
 At the very outset of this research effort, Margaret wrote, "If we could have such plates then we might have photographs of the complete neb. spectrum and photograph the Mg lines afterwards on the same plates as the neb. spectrum is on... At present our results are not too satisfactory: but I hope and believe we shall succeed in doing what we wish. It would be very important not to have to depend on eye observations in anything so difficult and important as that identity of Mg lines question," (M. Huggins, October 24, 1888, Notebook 2).
 M. Huggins, March 9, 1889, Notebook 2.
 W. Huggins and M. Huggins, "On Spectrum of Nebula in Orion," 48-49.
 Questions on this issue are raised by William Huggins' reaction to the news that Hertha Ayrton had just been voted the recipient of the prestigious Hughes Medal at a meeting of the Royal Society's Council. The day of the meeting Margaret, whether out of concern for her husband's health or interest in the outcome of the Council's vote, assessed William's health, and judged him too ill to attend. Given the turn of events, Huggins regretted having missed his chance to vote in opposition to the award. He complained to Joseph Larmor: "The papers will teem with publications from all the advanced women! I suppose the P[resident, Lord Rayleigh] will invite her [Ayrton] to the dinner, and ask her to make a speech. As the only lady--I should say woman--present, the P. will have to take her in, and seat her on his right hand! And all this comes from what appeared as the pure accident of my taking a chill on Wednesday.... Was it Providence on her behalf or was it 'the D-- taking care of his own'--which? Can we now refuse the Fellowship to a Medallist?" (W. Huggins to Larmor, November 2, 1906, Larmor Papers, Lm. 948, Royal Society of London Library, London.) See, Joan Mason, "Hertha Ayrton (1854-1923) and the Admission of Women to the Royal Society of London," Notes and Records of the Royal Society of London 45 (1991): 201-220; 214-216.
 Lockyer, "Appendix to Bakerian Lecture: Suggestions on the Classification of the Various Species of Heavenly Bodies," Proceedings of the Royal Society 45 (1889): 157-262; 200-201.
 W. Huggins, "Preliminary Note on the Photographic Spectrum of Comet b, 1881," Proceedings of the Royal Society 33 (1881): 1-3.
 W. Huggins to Stokes, January 22, 1889, Stokes Papers, Add MS 7656.H1235, Manuscript Room, Cambridge University Library, Cambridge, England.
 M.Huggins, n.d., but probably early 1889; added under June 30, 1881 entry, Notebook 2.
 John Ruskin, "Of Queens' Gardens," Sesame and Lilies (London, 1904), 107.