Chapter 6—Part 3

Eclecticism, Opportunism, and the Evolution
of a New Research Agenda:
William and Margaret Huggins and the
Origins of Astrophysics

Barbara J. Becker

A Dissertation submitted to The Johns Hopkins University
in conformity with the requirements for the degree of
Doctor of Philosophy
Baltimore, Maryland
1993

Copyright ©1993 by Barbara J. Becker
All rights reserved

CHAPTER 6—PART 3

SOLAR OBSERVATIONS AT TULSE HILL

Photographing the Solar Corona Without an Eclipse

In spite of growing threats of local unrest in Egypt, Arthur Schuster, the German-born spectroscopist whom we met in chapter 3, travelled to that country in May 1882 to observe an eclipse as part of an expedition headed by Lockyer.⁷⁷ The solar corona was, once again, the principal object of interest. Totality was expected to last only a little more than one minute. Nevertheless, the fact that the moon's shadow crossed over arid Egypt virtually guaranteed 100% visibility.⁷⁸ A strict division of labor and diligent practice would insure success.⁷⁹

By 1882, Lockyer had four eclipse expeditions under his belt, and had the advantage of having observed totality over the course of nearly one complete eleven-year sunspot cycle.⁸⁰ With the seventy-four seconds of totality promised in May, he wanted another crack at proving his theory that there was, in fact, no so-called "reversing layer" in the sun's atmosphere, contrary to Young's interpretation of what he had seen in the instant before totality back in 1870. Lockyer was also anxious to verify a theory he had developed following the 1878 eclipse which related coronal shape and structure with sunspot numbers. Following a few years in which almost no sunspots were seen (1878 having the least), 1882 had produced a relative bumper crop of sunspots, and at eclipse time, there were over twenty spots visible on the sun's surface.⁸¹ Lockyer predicted the corona in 1882 would bear a strong resemblance to the complex and highly textured corona he had seen in 1871, the last time he had observed an eclipsed sun with many sunspots on its surface.

While Lockyer was not altogether successful in his attempt to rid the sun of its reversing layer, he was elated by the appearance of the solar corona. In addition, Arthur Schuster obtained many fine photographs of the corona, including a first-time photograph of the coronal spectrum.⁸²

Meanwhile, in the spring of 1882, William and Margaret Huggins had been busy trying to photograph the spectrum of the Orion Nebula. On 7 March, they succeeded.⁸³ Their efforts were intensified following the appearance in May 1882, of a paper by Henry Draper, the American amateur astronomer, in which he announced his own success in taking two photographs of the Nebula's spectrum back in March.⁸⁴ The Hugginses were anxious to hold on to their priority in this difficult area of celestial photography.

Priority was a major concern of the Hugginses at this time. In April 1882, William had written to Edward S. Holden of the Lick Observatory. He wished to correct what he viewed as a serious error published in Simon Newcomb's book, Popular Astronomy, which stated that he (Huggins) and Father Angelo Secchi had simultaneously discovered the gaseous nature of the nebulae. In fact, Huggins argued, Secchi had no inkling of the existence of such lines until he heard about them from Otto Struve. Huggins wrote, "I had an account from Struve himself.... Struve visited Secchi & told him of my discovery. Secchi at first would not believe it, but ... in Struve's presence [Secchi] pointed [his instrument] to a nebula & saw one or more lines." Margaret Huggins added at the bottom, "And in the interests of morality I denounce Sechi's [sic] above proceeding as shameful thievery."⁸⁵

In consequence of these priority concerns, the Hugginses' interest in solar observation was at a very low ebb at the time of the Egyptian eclipse. That is, until they read the eclipse report in the London Times which told of Schuster's pronouncement that he had found the violet region of the spectrum, near Fraunhofer's lines H and K, to be the brightest part of the coronal spectrum.⁸⁶ Margaret and William Huggins later claimed that they quickly recognized that this information held forth a means for photographing the corona without an eclipse and accordingly set to work. In a lengthy notebook entry dated 15 December 1882, Margaret recounted the history of their efforts over the past several months:

It at once occurred to us that the principle propounded by William in 1866-8 in his endeavours to see the prominences without a prism -- viz that using absorbing media for all except a limited part of the spectrum and so reducing the amount of glare from our atmosphere against which a bright object behind it of which the spectrum is that having the same refrangibility as themselves. The principle although sound failed as regards the prominences because it proved impossible (up to this time) to find any media which together would absorb the whole spectrum close-up to C on either side. It might however we thought be successfully applied to photographing the Corona the spectrum of which was clearly brightest through some little range about H and K.

There are no notebook entries contemporaneous with any of the Hugginses' efforts to photograph the solar corona in 1882. Margaret's 15 December entry of over seven handwritten pages (not including space devoted to brief notes added at later dates) provides a cursory summary of this work and curiously bridges a major chronological gap in the Hugginses' notebook entries.⁸⁷

Guided by Schuster's claim that the coronal light was strongest in the violet, the Hugginses contrived a way to filter out all other colors from the solar spectrum hoping in this way to render the corona visible without an eclipse. They took three or four pieces of violet glass, cemented them together with some castor oil to prevent light loss from reflection, and placed them in front of the light sensitive film in their photographic apparatus.⁸⁸ Initially, they used a refracting telescope to focus the light, but early trials heightened their concern about chromatic aberration, a blurriness found in all images formed by lenses owing to the fact that transparent materials disperse the light that passes through them. Instead of forming one image at a single point, a lens produces an array of images, each of a different color, clustered in a region around its ideal focal point. While the severity of this blurriness can be minimized by a skilled optician, it can not be entirely eliminated in an optical instrument constructed of refracting elements; reflection, on the other hand, is a non-dispersive means of redirecting light. The Hugginses switched to a reflector.⁸⁹

At the Royal Society's soirée on 21 June 1882, plates from the Egyptian eclipse expedition were shown. It was at this time that Margaret and William were actually able to see the evidence from which it had been deduced that the violet region of the coronal spectrum was the brightest. Margaret wrote: "We then set to work and on every fine day when we could be sure of the Sun for a few moments free from clouds we took photographs of it with varying exposures."⁹⁰ Their photographic investigation of the sun continued through the end of September 1882, and a total of twenty plates were obtained on which "a form peculiarly coronal is to be seen."⁹¹ In comparing these photographs, they asserted that

upon the whole the correspondence is striking; and careful measures of the average height of the outer and inner corona in the Egyptian plates and in ours agree in the relative proportions they bear to the diameters of the suns in the two sets of plates.⁹²

Margaret added that they planned to continue these experiments using a black disk the same size as the sun's image in front of the stack of absorbing material in order to further reduce glare.

In the fall 1882, Huggins shared the photographs with George Stokes, hoping, it seems, to get some supportive response from the experienced spectroscopist and esteemed Secretary of the Royal Society. Stokes clearly missed what Huggins had hoped might be obvious. Huggins therefore wrote a lengthy letter providing Stokes with some guidance in "seeing" the photographs:

I write now in the hope that you will once more look at the photographs as you do not seem to have seen what we see. If we had merely seen the little difference of illumination immediately about the sun's image, I should at once have considered it of too slender importance, & I would not have troubled you with the photographs.

My wife & I, independently, see in all the photographs (in which we see the appearance at all) a definite form of difference of illumination which is essentially the same in all the phots. taken at different times, with different plates, & different absorbing media....

I have just looked at one of the ten good plates I have here, & I see it perfectly. My wife has done her best to make a drawing of this form (necessarily a little exagerated [sic] in distinctness) relatively to the shape of the plate. It should correspond on the other plates except in the cases in which the plates were placed at right angles to the usual position....

Will you kindly examine one of the photographs carefully in different lights until you are able to see the definite form such as is shown in the enclosed sketch. When you have seen it in one photograph, I think you will not have much difficulty to discovering exactly the same complex & peculiarly coronal form of outline in all the others.⁹³

In case that did not provide Stokes with sufficient help and encouragement, Huggins added in a postscript:

My wife has been careful not to put more in than she sees. I confess I think I can see rather more structure & can trace the appearance rather farther from the sun's limb. My wife has added notes of her own.

The appearance is more distinct on one side, this is not out of harmony with what has been seen at eclipses.

The drawing corresponds with the photographic plate when laid over it, with the gelatine side uppermost. As the little camera is not permanently attached to the telescope, it is possible it was not always attached quite accurately in same position.

At some point in the next few weeks, Huggins must have received the positive response he wished from Stokes,⁹⁴ for he soon informed Schuster of his apparent success.⁹⁵ He also invited William de W. Abney, the photographer whose plates were used during the Egyptian eclipse, to his home to examine the photographs of the corona without an eclipse. Abney was sufficiently impressed with the similarity in appearance of what Huggins claimed to be the corona in his photographs and that captured on film during totality in Egypt. Not only are the general features the same, Abney wrote to Huggins, "but also ... details such as rifts & streamers have the same position and form."⁹⁶ Abney went so far as to claim, "If in your case the coronal appearances be due to instrumental defects, I take it that the eclipse photographs are equally untrustworthy."⁹⁷ Margaret later recorded her recollection that Abney told William, "As surely as I stand here, you did photograph the Corona."⁹⁸

On 13 December 1882, William Huggins submitted a paper to the Proceedings detailing this work. In it he complained that the climate in England was "unpropitious" for such observations. A few months later, in a report to the RAS, Huggins suggested trying this method in a location with clearer skies, perhaps at a higher elevation to avoid the obscuration of the thicker layers of earth's atmosphere. If the method worked, Huggins claimed, "the corona may be successfully photographed from day to day with a definiteness which would allow for the study of the changes which are doubtless always going on in it."⁹⁹

The Hugginses replaced the Short reflector with a 7-foot Newtonian lent them by the daughters of William Lassell (see Figure 36). This telescope produced larger and less distorted solar images. William and Margaret photographed the sun at every possible opportunity. But during the spring of 1883, they were hampered by wet weather.¹⁰⁰ They were particularly interested in obtaining some good photographs of the corona without an eclipse on or about 6 May 1883. This was the date on which a solar eclipse of exceptionally long duration had been predicted to cross the Pacific Ocean making landfall on a small coral island in the Marquesas.¹⁰¹ The island, called Caroline Island, was only 7-1/2 miles long and 1/2-mile wide. In spite of the difficulty in getting there and the uncertainty of the weather, a number of observers came from around the world to view this particular eclipse. Among them were two representatives from the Royal Society, H. A. Lawrance and C. Ray Woods, both assistants to Lockyer at South Kensington. They were charged with photographing the corona during the eclipse. Huggins anticipated that a comparison of Lawrance's and Woods' corona photographs with those he planned to take on the same day back in London would conclusively demonstrate the validity of his method.

Figure 36. Schematic drawing of 7-1/2 foot Newtonian reflecting telescope loaned to William Huggins by Jane and Caroline Lassell for the purpose of photographing the solar corona without an eclipse [from Rept. Brit. Ass. (Southport, 1883): 347].

While conditions were favorable for eclipse observers on Caroline Island, bad weather in London that day precluded the taking of any photographs at Tulse Hill. In the Hugginses' opinion, they had succeeded in capturing what they believed were good images of the corona on three other dates (3 April, 31 May, and 6 June) that were close enough to 6 May to enable the Hugginses to justify using them as substitutes. Huggins gave these photographs to the talented illustrator and RAS Assistant Secretary, William Wesley, who had had considerable experience over the previous decade converting photographic plates of solar eclipses into reproducible drawings for the RAS's ambitious volume 41 of its Memoirs which detailed the history of solar observation.¹⁰² At Huggins' request Wesley also made drawings of the coronal photographs taken at Tulse Hill.

Upon their return from Caroline Island, Lawrance and Woods were first shown Wesley's drawings and then shown the negatives from which the drawings were made.¹⁰³ The two men were impressed with the similarities between their results and the images Huggins had captured without an eclipse. Particularly notable in all the images, in their opinion, was evidence of a rift in the corona near the sun's north pole. Lawrance wrote to Stokes, "As a result of the comparison I should say that Dr. Huggins' coronas were certainly genuine as far as 8' from the limb."¹⁰⁴

This test of the efficacy of Huggins' method of examining the corona yielded inconclusive results. To try it again meant waiting for the next convenient solar eclipse. Another was coming up in September 1885 (cutting across New Zealand), but Huggins did not want to wait that long, nor did he want to count on the whims of the weather to make a direct comparison possible. Instead, he devised a new plan which did not involve making a comparison against the corona during eclipse. Huggins believed that obtaining a large number of coronal images with a high degree of internal consistency would verify the method's validity. To do this efficiently, however, required a more favorable and less fickle environment.

In December 1883, at the urging of two other Fellows of the Royal Society, Huggins sent a note to the Government Grant Committee of the Royal Society, to suggest that a sum of about £200 be allocated to finance a small expedition to a place like Switzerland which was both easy to get to and located at a high elevation.¹⁰⁵ A party of experienced photographers -- the men who went to the Caroline Island eclipse, for example -- could spend two or three months on a mountain in Switzerland free of lower atmospheric obscuration and gather many photographs.

Hoping to gain an ally, Huggins outlined his plan in a short note to Stokes. Huggins was, himself, a member of the Grant Committee and he recognized the delicacy of the situation and the possible questions of conflict of interest that could be raised given his own personal stake in the results of such an expedition. He was careful to assure Stokes "I do not want to have any personal grant. If it is done, it must be by means of a committee who would be (not I) responsible for the use of the money."¹⁰⁶

William Huggins was clearly excited about how things were going thus far: Abney and Stokes had given him written statements attesting to their belief in the authenticity of his original coronal photographs, Lawrance and Woods had compared his more recent coronal photographs quite favorably with those they had taken during the eclipse at Caroline Island, and now he was being encouraged to pursue the matter further and apply for a grant from the Royal Society to obtain even more persuasive evidence of the validity of his new method.¹⁰⁷

While he waited for the Government Grant Committee to consider his request, Huggins continued to search for ways of drawing more evidence out of the three photographs taken around the time of the 6 May 1883 eclipse. He wrote to Stokes in January 1884 "In confidence for the present." Seeing Wesley's drawings of his photographs had done much to heighten Huggins' own conviction that the images he had obtained showed the corona. He began to calculate probable changes in appearance of the solar corona based on known rates of solar rotation and the assumption that the corona moved with it:

In three of the drawings from my plates there is a very marked V shaped rift which is the most conspicuous feature of the Eclipse photograph.... Now if we take the synodical rotation of Sun at 27 days (there is a little uncertainty about Sun's rotation say 25.2 days), the successive positions of the rift are not far from where we should expect them to be. The rift itself seems to widen out either in reality or from perspective. It is least distinct on April 3, & widest & strongest on June 6. Of course it may be that the rift has not rotated, but shifted toward the axis from the first plate on April 3.

When I get back the plates I may be able to find the rift on the other side of the axis on some other plates. Mr. Wesley has concentrated his attention on the plates he selected to draw from. He is about to take the drawings to Prof. Bonney to have them engraved. It seems to me that it would be desirable for me, when I get back the plates, to see how much can be got out from them & to put the results in a little paper for the Proceedings. If I do this it would be necessary to have copies of the plates. No doubt the B. Ass. would allow the R.S. to have copies taken. I think they will be engraved in steel. The drawings contain much more detail than those you saw. The plates have been strengthened & Mr. Wesley has had Captain Abney's assistance. I was careful not to influence Mr. Wesley myself.¹⁰⁸

The letter included a set of small sketches showing the position of the apparent rift in the corona which Huggins claimed was visible in the photographs from 3 April, 31 May, and 6 June 1883 (see Figures 37, 38, and 39). He expanded upon these claims in a lengthy letter to Holden in June and conjectured that the persistence of the rift over several rotations of the sun was indicative of something relatively permanent in the structuring of physical forces in the near solar environment.¹⁰⁹ Margaret, clearly seeing their coronal work opening new avenues of solar research added, "Astronomical prospects grow wider and wider...."

Figure 37. Sketches of coronal features from photographs by William Huggins (from Huggins to Stokes 2 January 1884). Compare with William Wesley's drawings in Figure 38.

Figure 38. Drawings by William Wesley of solar corona without an eclipse from photographs taken by William Huggins [from Rept. Brit. Ass. (Southport, 1883): Plate X].

Figure 39. Drawing by Willliam Wesley of total solar eclipse, 6 May 1883, from photograph by Ray Woods [from Rept. Brit. Ass. (Southport, 1883): Plate XI].

In May, possibly to influence the decision to fund the expedition to Switzerland, Huggins wanted Wesley's drawings to be displayed at the upcoming Royal Society soirée. He wrote to Wesley on the all important matter of their display. Huggins thought it would be best to place the drawings under glass, so they could not be touched, and in a location where they could be illuminated properly. It would be advisable, he thought, to accompany the drawings with a "good sized label calling attention to the rift" to guide viewers' inspection of them.¹¹⁰ He also thought it wise to include some notice of the drawings in the evening's printed program to draw them to people's attention. Huggins concluded his note by requesting that Wesley bring the drawings to the Royal Society a little early in order to "choose the best position for light, so much depends upon this. They should have a lamp to themselves."¹¹¹ Shortly after the soirée, Huggins presented the collection of Wesley's drawings to the Royal Astronomical Society. He did not wish to have them in his possession out of concern for later accusations that he had altered them.¹¹²

The Royal Society awarded a £250 grant to send an experienced photographer to Zermatt, Switzerland, to replicate the Hugginses' method of photographing the solar corona without an eclipse at a location of extremely high elevation. The location selected was the Riffel with an elevation of 8,500 feet. The photographer chosen was Ray Woods, whose experience in photographing the solar corona at both the recent Caroline Island eclipse and the Egyptian eclipse of 1882 made him the logical choice.¹¹³

Woods consulted with both Huggins and Abney in order to master Huggins' photographic technique, which, by then, Huggins believed he had improved. He had eliminated the filtering material entirely. Instead, Huggins planned to rely on selective sensitivity in the photographic plates themselves to capture light from the desired narrow region of the solar spectrum. Woods arrived on the mountain in July 1884 and soon set to work. He took photographs of the sun until 21 September. Unfortunately, this was not an auspicious time to be trying such a delicate and exacting process. The advantage of clear skies to be gained in such a climate at such an elevation was lost by the chain of volcanic eruptions in Indonesia during the summer of the previous year.

Beginning in May 1883, a cloud of vapor issued out of Mt. Krakatoa, the 2700 foot high centerpiece of an uninhabited volcanic island roughly the size of Manhattan located just off the coast of Java. It was estimated that the cloud may have reached a height of nearly seven miles. In mid-June and again in July, the mountain showed signs of activity. On 26 August in the early afternoon, a continuous series of volcanic eruptions, earthquakes, and tsunamis rocked the region for nearly 22 hours. The next morning, the island of Krakatoa exploded with a blast that was heard nearly half-way around the world. All told, nearly 40,000 people are believed to have been killed in the disaster.

Volcanic eruptions in our own times have demonstrated the profound impact large quantities of fine debris injected into the upper atmosphere can have on astronomical observations.¹¹⁴ The material from Krakatoa quickly encircled the globe bringing brilliant sunsets for artists and poets, but wreaking havoc on the plans of astronomers in need of transparent skies, even as long as a year later. As Huggins later complained, "It is most certainly matter in the wrong place so far as astronomical observations are concerned."¹¹⁵

In Switzerland, Woods reported often seeing a great aureola around the sun with a diameter of about 44?.¹¹⁶ In spite of the annoyance of this atmospheric phenomenon, Woods obtained about 150 photographs, of which half showed the general form of the solar corona and a few even had what he considered indications of detailed coronal structure.¹¹⁷ Huggins was pleased with the initial results in spite of the "quite exceptional state of the sky."¹¹⁸ In his excitement, Huggins wrote Holden: "It seems of the first importance that the method be adopted at some elevated observatory."¹¹⁹ Where that might be, and under whose sponsorship was unclear at that point.¹²⁰

Perhaps Huggins' mind was on the new Lick Observatory being built on the 4209-foot high Mt. Hamilton in California when he wrote these words. He had long been aware, and to some extent even involved in the plans for this observatory financed by the wealthy and eccentric American investor, James Lick. In July 1874, Lick had formally set up a trust to build an observatory to house what he hoped would be "a powerful telescope, superior to and more powerful than any telescope ever yet made."¹²¹ Huggins' correspondence with American astronomers increased in the early 1880s reflecting his respect and, perhaps even his concern, for the growing potential held by such large telescopes located at high elevations. Huggins wished his American colleagues to know of his breakthrough in photographing the solar corona without an eclipse. In December 1882, he wrote to Edward Pickering of the Harvard Observatory.¹²² In January 1883, Margaret wrote to Edward Holden at the Washburn Observatory.¹²³ When Benjamin Apthorp Gould, an American astronomer currently directing the Cordoba Observatory in Venezuela, visited London to receive his Gold Medal from the RAS, Huggins showed him the photographs he had taken.¹²⁴

Selecting an appropriate site would certainly play an important role in the success of any future efforts to photograph the solar corona without an eclipse, but the sensitivity of the method required that only one specially trained in it could be entrusted with its execution. In Huggins view, Ray Woods was one such individual. Huggins confided in Holden that David Gill, the Director of the Cape Observatory, was hoping to lure Woods to work with him there. Huggins hoped that Holden, in planning for his future staff at the Lick, might make Woods a counter-offer, of say, £250 to £300, and tempt him to spend some time at the Lick Observatory still under construction.¹²⁵ Huggins did not want Woods' special talent to be diverted to other projects. Besides, having a good photographer like Woods at an observatory where the skies were clear would mean a program of solar corona photography could be carried out on a regular basis.

Gill succeeded in getting Woods to come to the Cape to serve as his assistant.¹²⁶ Woods' move to the Cape worked to Huggins' advantage in the end, despite his earlier anxieties. In November 1884, it was announced at the Royal Society's anniversary meeting that a special grant from the Government fund had been awarded to Gill to take a "series of daily photographs of the Solar Corona," a project which was to be carried out by Ray Woods.¹²⁷ With the potential for as many as 350 days of clear sky each year, the Cape could prove to be the ideal place to conduct the kind of coronal study Huggins desired.¹²⁸

NOTES
[click on footnote number to return to text]

77. On 17 May, the day of the eclipse, England and France sent a fleet of ships to Alexandria to restore order in the wake of a popular uprising against the Khedive, the Egyptian ruler whose pro-European sympathies were under attack. The unrest continued throughout the summer and Europeans were forced to flee Alexandria. The next day there were numerous reports in the London Times under the headline "Latest Intelligence" with news of "The Eclipse Expedition" and "The Crisis in Egypt" given from many different national perspectives. See, London Times 18 May 1882 (5). Fortunately, the expedition returned to England without mishap. Henry Roscoe wrote to Schuster: "We only trust that you have escaped safely from Egypt where it seems that things are likely to turn out pretty awkward." Henry Roscoe to Arthur Schuster, 2 June 1882, Sc. 158, Schuster papers, Royal Society Library.

78. J. Norman Lockyer, Chemistry of the Sun (Macmillan & Co.: London, 1887): 359.

79. Clerke, History of Astronomy, 226.

80. Lockyer had thus far travelled to observe eclipses in 1870, 1871, 1875 and 1878.

81. Clerke, History of Astronomy, 226.

82. Ibid., 226-7.

83. William Huggins to George Stokes, 7 March 1882, Add MS 7656.H1148, Stokes papers, University of Cambridge Library; William Huggins to W. C. Christie, 7 March 1882, Royal Astronomical Society correspondence, Royal Astronomical Society Library. The notebook entry recorded by Margaret Huggins and dated 7 March 1882 was clearly written some time after the fact and contains much pointed criticism of Henry Draper and his efforts to obtain the same result. See, Margaret Huggins, 7 March 1882, Notebook 2.

84. Henry Draper, "On Photographs of the Spectrum of the Nebula in Orion," American Journal of Science 23, 3rd Series (1882): 339-41.

85. William Huggins to Edward S. Holden, 10 April 1882, Mary Lea Shane Archives of the Lick Observatory.

86. "The Eclipse Expedition," London Times, 19 May 1882 (5d). It would be interesting to subject Schuster's claim to scrutiny in light of modern views regarding the sources of visible light produced in the sun's upper atmosphere. One component, a faint continuous spectrum, is recognized by astronomers today as coming from photospheric light scattered from free electrons in the corona. It mimics the visible solar spectrum in relative intensity of individual wavelengths. Thus, it has a maximum around 4900Å which is in the yellow-green region of the spectrum. Another component of the modern visible corona is an emission spectrum generated by high-temperature ions in the corona. It contains a few discrete bright lines, many of which are only visible during periods of unusual solar activity. The most prominent coronal emission line is the green "1474" line discussed earlier in this chapter and which was first observed by Charles Young in 1869. A third component of the visible light seen in the corona from earth bears mentioning here. Seen as an extremely faint replica of the sun's absorption spectrum, it is now accepted as being produced by photospheric light reflecting off debris in the ecliptic plane. Known as the zodiacal light, this component of the visible corona, is unrelated to physical processes in the solar atmosphere.

87. There are no regular entries in the Hugginses' notebooks from June 1882 until April 1886, the lengthy and retrospective 15 December 1882 entry being a notable exception. When the entries begin again, they are written in William's hand. Margaret did not resume her role as notetaker until November 1886. There is no explanation given for this in the notebook.

88. Flaws in the violet glass encouraged Margaret and William to change the absorbing material to a smooth glass container filled with a solution of potassium permanganate.

89. The reflector the Hugginses used was not the 18-inch Grubb had made, but an old telescope by James Short which had a 6-inch aperture and a 3-foot focal length. In early March 1882, Huggins had written to Edward Knobel, then Secretary of the RAS, to say that he was in need of a reflecting telescope of about 4-inches in aperture for some new experiments. He wanted to know if the Society might have such an instrument available for loan. In any case, Huggins wished to have sent to him the address of the individual who had offered such an instrument for sale at the last RAS meeting.

90. Margaret Huggins, 15 December 1882, Notebook 2.

91. Ibid.

92. Ibid.

93. William Huggins to George Stokes, 12 November 1882, Add MS 7656.H1152, Stokes papers, University of Cambridge Library.

94. The letter from Stokes does not survive, and hence cannot be firmly dated. However, Huggins cited a brief excerpt from it as evidence in support of his interpretation of the photographs in his Proceedings paper: "The appearance is certainly very corona-like, and I am disposed to think it probable that it is really due to the corona." See, William Huggins, "On some Results of Photographing the Solar Corona without an Eclipse," Proceedings of the Royal Society 34 (1882): 409-14, 412-3.

95. William Huggins to Arthur Schuster, 2 December 1882, Sc. 96, Schuster papers, Royal Society Library.

96. William de W. Abney to William Huggins, 15 December 1882, inserted in 15 December 1882 entry, Notebook 2. This letter is reproduced with a few alterations in Huggins, "On some Results of Photographing the Solar Corona without an Eclipse," Proceedings of the Royal Society 34 (1882): 409-14; 414.

97. Huggins substituted the word "causes" for "defects" when citing this letter in his Proceedings paper.

98. This anecdote is included in a series of undated notes added to the lengthy 15 December 1882 entry in Notebook 2 and which, given the dates mentioned in them, were probably written in 1888. Its inclusion at this late date is indicative of the continued weight the Hugginses wished to place upon Abney's initial response to seeing their photographs even though Abney later became skeptical of the photographs having genuinely shown the corona.

99. [William H. M. Christie], "Dr. Huggins' Method of Photographing the Solar Corona without an Eclipse," Report of the Council, Monthly Notices of the Royal Astronomical Society 43 (1883): 231-2; 232.

100. William Huggins to George Stokes, 13 May 1883, Add MS 7656.H1159, Stokes papers, University of Cambridge Library; William Huggins to Edward S. Holden, 14 September 1883, Mary Lea Shane Archives of the Lick Observatory.

101. This eclipse, with a totality approximately 5-1/2 minutes long, is a member of a notorious family of long eclipses (Saros 136). This eclipse group was recently brought to the public's attention on 11 July 1991, when another eclipse in the same series (totality, just under 7 minutes duration!) again crossed the Pacific Ocean. In 1991, the eclipse crossed a number of populated regions, and because of advance publicity, was seen by millions of people. See Clerke, History of Astronomy, 230-3; Guy Ottewell, The Under-standing of Eclipses (Astronomical Workshop: Greenville, 1991): 87.

102. For a discussion of how this remarkable volume came to be written, see Pang, Spheres of Interest, 334-41.

103. The order in which the visual evidence was presented to Woods and Lawrance may have been crucial in shaping their opinion of the reality of the effect depicted.

104. "Dr. Huggins' Method of Photographing the Solar Corona without an Eclipse," Report of the Council, Monthly Notices of the Royal Astronomical Society 44 (1884): 203. See also, H. A. Lawrance to George Stokes, 14 September 1883, included in letter from William Huggins to Edward S. Holden, 9 October 1883, Mary Lea Shane Archives of the Lick Observatory.

105. Huggins described this note in a letter to Stokes. See, William Huggins to George Stokes, 12 December 1883, Stokes papers, Add MS 7656.H1167, University of Cambridge Library.

106. Ibid.

107. For some indication of Huggins' excitement, perhaps even a hint at the "bumptiousness" Crookes had noted in his personality a decade earlier, see Huggins' letters to William Wesley and T. G. Bonney regarding the engravings to be made of his photographs: William Huggins to T. G. Bonney, 20 December 1883, MM 7.4, Royal Society Library; William Huggins to William Wesley, 22 December 1883, Correspondence, Royal Astronomical Society Library.

108. William Huggins to George Stokes, 2 January 1884, Add MS 7656.H1168, Stokes papers, University of Cambridge Library.

109. William Huggins to Edward S. Holden, 2 June 1884, Mary Lea Shane Archives of the Lick Observatory.

110. William Huggins to William Wesley, 5 May 1884, Correspondence, Royal Astronomical Society Library.

111. Ibid.

112. William Huggins to E. B. Knobel, 9 May 1884, Correspondence, Royal Astronomical Society.

113. "Dr. Huggins's Method of Photographing the Solar Corona without an Eclipse," Report of the Council, Monthly Notices of the Royal Astronomical Society 45 (1885): 258-9.

114. The eruption of Mexico's El Chichon in March and April 1982, for example, put so much material into the upper atmosphere (particularly in the Northern Hemisphere) that the total lunar eclipse in July of that year was notable both for its unusual darkness and the asymmetry of its appearance. Mt. Pinatubo's eruption in June, 1991 caused colorful sunsets the world around and lengthened the average evening twilight for many months as sunlight scattered from particles located as much as sixteen miles above the earth's surface. See Aden Meinel and Margorie Meinel, Sunsets, Twilights, and Evening Skies (Cambridge University Press: Cambridge, 1983): 39-61.

115. William Huggins, "On the Solar Corona," Proceedings of the Royal Institution 11 (1885): 202-14; 209.

116. Similar phenomena were noted by others. In particular, the Reverend S. E. Bishop, writing shortly after the Krakatoa eruption in September 1883, noted a "very peculiar corona or halo" around the sun with many characteristics similar to those remarked upon by Woods. Now known as Bishop's Ring, such unusual atmospheric effects are most often observed when fine volcanic ash has been injected into the upper atmosphere. See Meinel and Meinel, Sunsets, Twilights, and Evening Skies, 79-81, and Plate 8-1. In Huggins' circle, William Abney attributed the aureola to ice crystals, although, others, whom Huggins called the "Krakatowa-ites," blamed it on the volcano. See William Huggins to Edward S. Holden, 29 October 1884, Mary Lea Shane Archives of the Lick Observatory. Interest in the Krakatoa event was stimulated in Britain by accounts provided by seamen located close enough to the island at the time to have witnessed the eruption's destructive force firsthand. The Royal Society formed a committee to study the matter. Its report, The eruption of Krakatoa and subsequent phenomena, was published in 1888.

117. "Dr. Huggins's Method of Photographing the Solar corona without an Eclipse," Report of the Council, Monthly Notices of the Royal Astronomical Society 45 (1885): 258-9.

118. William Huggins to George Stokes, 4 October 1884, Add MS 7656.H1171, Stokes papers, University of Cambridge Library.

119. Huggins to Holden, 29 October 1884, Mary Lea Shane Archives of the Lick Observatory.

120. By the time Woods returned from Switzerland, Abney had spent all the money appropriated for this project by the Royal Society. If Wesley was to be asked to convert the photographs to drawings, more money would have to be requested. Huggins wrote to Stokes to ask for an additional £20 for this purpose from the donation fund. See, Huggins to Stokes, 4 October 1884, Stokes papers, University of Cambridge Library.

121. William Wallace Campbell, A Brief Account of the Lick Observatory of the University of California (University of California Press: Berkeley, 1927): 3-17.

122. William Huggins to Edward C. Pickering, 22 December 1882, Pickering papers, Harvard University Archives.

123. Though still director of the Washburn Observatory in Madison, Wisconsin, Holden was the designated future director of the Lick. Holden seems to have met the Hugginses during a trip to London in the summer of 1876 (see, Edward S. Holden to Henry Draper, 2 August 1876, Draper papers, New York Public Library). Afterwards, the Hugginses maintained a friendly relationship with Holden by mail.

124. Huggins reported to George Stokes that after viewing these photographs, Gould was "convinced that the appearance was really the corona." See, William Huggins to George Stokes, 13 May 1883, Add MS 7656.H1159, Stokes papers, University of Cambridge Library.

125. It is interesting to note that Huggins had originally written £200 to £250, but scratched these out and inserted the higher numbers in the space above.

126. The Lick Observatory was by this time, some ten years in the planning and building. The 12-inch Clark refractor was installed within its small dome in time for the transits of Mercury and Venus in 1881 and 1882 respectively, but those were singular events. No routine observations were carried out until all the construction and instrument-making was completed in 1888. Its official scientific operation began on 1 June 1888. Even if Woods had wanted to forego his opportunity to work with Gill at the Cape, there would have been little to do at the Lick for almost four more years! See, Campbell, A Brief Account of the Lick Observatory, 6-11; Osterbrock, Gustafson, and Unruh, Eye on the Sky, 38-43; 53-63.

127. "Dr. Huggins's Method of Photographing the Solar Corona without an Eclipse," Report of the Council, Monthly Notices of the Royal Astronomical Society 45 (1885): 258-9.

128. Kevin Krisciunas, Astronomical Centers of the World (Cambridge University Press: Cambridge, 1988), 195-6.

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