Eclipse Expeditions: From HCO and SAO out into the world

The eclipse of 21 August 2017 offers us the chance to witness a rare and awesome spectacle. The aesthetics of such an event have always excited the casual observer, but astronomers and other scientists often sacrifice the immediate visual beauty for their observations, by which interpretations they can illuminate a more subtle cosmic beauty. Since its inception in the early 1800s, and even before, Harvard College Observatory has sent expeditions to the path of totality: to Sweden, Kentucky, California, Grenada, Peru, and even Mauritania in eastern Africa. Here too in Cambridge our astronomers have observed solar eclipses, although we have never been graced with totality.

Our new exhibit tells the stories of eclipse expeditions from the Harvard College Observatory (HCO) and Smithsonian Astrophysical Observatory (SAO): with maps whose calculations have been painstakingly verified and beautifully illustrated to show the path of totality; with instrumentation lists, notes and diaries of observers, which range from simple recording to poetical reactions; to the final image of the eclipse, whether sketched or photographed, with which astronomers compared findings and discussed conclusions.  

For a limited time, see some of the earliest artifacts from the founders of the HCO, the Bond family. For the solar eclipse of 28 July 1851, George Phillips Bond travelled to Lilla Edet, Sweden, and kept a travel journal in which he recorded his observations and illustrated the “rosy prominences” that he saw in the sun’s corona. Meanwhile, back in Cambridge, this partial eclipse was daguerreotyped by John Adams Whipple, who worked with the Bonds to create some of the earliest cosmic photographs. These items, due to their age and delicacy, will only be displayed for a short time, so be sure to stop in before August 30!

Fig 1 : Map of the total solar eclipse of 8 July 1842, over eastern Europe.

        No official expedition was dispatched from Harvard to Europe for the total eclipse of 8 July 1842. But our astronomers were still able to work with the observations and data that European observers had distributed. One particularly enthusiastic eclipse observer in Boston, Robert Treat Paine, received this map of the path of totality from the authors (Fig. 1). It is an important tool for an observer planning an expedition: it provides information about the region from historical weather records, major geographic obstacles, the time calculations for the moments of contact, and the degrees of coverage in the region, including the path of totality. This sort of tool is still useful today: you’ve likely seen the maps published by NASA of the path bisecting the continental United States.

Robert Treat Paine was a big name in New England, especially among the astronomical community. His grandfather had signed the Declaration of Independence and served on the Supreme Court, and his father was a popular writer and poet. Inspired by the sight of a comet in his youth, Paine pursued his interests in astronomy as a lifelong hobby. In 1846, he joined future president John Quincy Adams and other notable Bostonites on a committee to determine the name, purpose, and extent of the recently established astronomical observatory at Harvard College. Here, he found the tools and devoted professionals to indulge his cosmic passions. Under construction, the new 15-inch refractor was about to be the biggest telescope in North America, and the Bond family, who headed operations, needed all the assistance they could get.

Paine had a particular interest in the movement of the moon, and so he never spared any expense to witness an eclipse. While he never received external funding for travel or research expenses, nor any formal scientific education, he still made upwards of 10 expeditions to the moon’s shadow, where he focused more on his experiments and calculations than the visual beauty. A story from his obituary relates one trip Paine took in 1880, from Boston to Sycamore, California. Sixty-seven years old, traveling alone, and “comparatively infirm,” he disembarked the train in a deserted, treeless prairie. His goal was to time totality, which he had calculated to be about 37 seconds. For that half-minute, he watched his clock. And when the sun came back, he turned around for Boston: “He returned, after his journey of six thousand miles, entirely satisfied, since he had secured his observations, although he can scarcely be said to have seen the eclipse.”

While individual astronomers like Paine never waited for institutional legitimacy to venture out to observe eclipses, the Harvard Observatory did not send any official expeditions until 1851, when George Phillips Bond travelled from Cambridge to Lilla Edet, Sweden to observe the total solar eclipse of 28 July. After setting out from Boston in the late spring, Bond spent the early summer traveling around England, France, and Germany, visiting important astronomical observatories, where he would discuss their observations, methods, publications and library collections. At the time he set out, the Harvard College Observatory was still young and vying for a professional name in astronomy. Formed in 1839, the observatory was 11 years old in name, but they had not begun innovative observations until the installation of the 15-inch great refractor telescope in 1847. Bond’s expedition provided the best opportunity for the Observatory to learn from peer institutions, and spread the name and goodwill of the HCO. On his trip, he met with the Royal Astronomical Society, Lord Rosse, John Herschel, Leverrier, and many other great scientific minds. Of course, he also found the time to be a tourist: during his time in London he frequented the legendary ‘Crystal Palace,’ built for the Great Exhibition of 1851, with which he was so enamored that he said, “anyone who is not satisfied had better find another world to live in than ours, where the art of man can go no further.” He was less enthusiastic about the “so called great masters” in the Louvre…

Bond arrived in Sweden a few days before the eclipse, time which he spent surveying the hills around the small village of Lilla Edet for a good viewing spot. This was made difficult by drenching rains and incessant dampness that disheartened Bond, both in spirit and body. Feeling unwell the day before the eclipse, Bond hardly had the time to practice his observations for the fleeting phenomenon. On the day of the eclipse, Bond was incredibly disappointed: “It was as if rain were a new art, and the clouds liked the novelty of it.” So disheartened, Bond gave up the prospect of observations until an hour before the event was to begin, when the clouds began to break. Bond had a small crew of assistants with him for this expedition, European colleugues or locals recruited to assist measurements and man various observation points. Since he was traveling for the better part of a season, Bond did not bring along intense instrumentation; rather, he simply had a small telescope that he could set up in a moments notice, a tool he had only just borrowed from the Hamburg Observatory. So on the summit of the ridge outside of town, he set up his telescope to see the first contact of moon and sun. And as the clouds cleared his view of the sky, he began to see out into the valley below him and mountains beyond, green, animals grazing, and “the inhabitants dressed in their best clothes occupying the hilltops and coming out into the streets.”

Beautiful, but that’s not what Bond travelled halfway around the world to see. In order to get a steady and (somewhat) comfortable view of the sun through his telescope, Bond had to lie flat on the ground, with his head supported by a pillow of stones. This gave him the view he was looking for. In the time leading up to totality, Bond describes his observations of sunspots, lunar mountains, and Baily’s beads of light, at seeing whose motion he exclaimed “oh that is something new!” When the moon covered the sun, Bond “threw” off his glasses to behold the corona: “Language is utterly powerless to describe that four minutes. I cannot picture a sight more awfully glorious on this side of heaven. An hour before, I could have smiled at what I now feel far too little to say of this scene of fearful beauty.”

Nevertheless, Bond describes the “sublimity” of his observations and experiences for several pages. He spent most of his time observing the “rose colored prominences” that jetted out from the ring of light. Looking closely at their base where they met the sun, Bond noticed that, unlike diagrams he had recently seen in the Memoirs of the Royal Astronomical Society, the surface and structure of the sun were not perfect, circular maps of light, “but composed of crooked fibres, or rather of irregular cords of rose colored light.” He sketched two diagrams of the total phase and the rosy prominences, which we have on physical display for a limited time (Fig. 2). About these, Bond says that “the flames are too large, and too deep a red.” Of particular interest to him, he noted how these prominences grew in size and deepened in color as the event progressed, until they exploded in a flash with the return of the solar body.

Fig 2 : Expedition journal of George Phillips Bond for eclipse of 28 July 1851, Lilla Edet, Sweden. From Harvard University Archives.

After the total phase, Bond did not wait to observe the rest of the phenomenon. He packed up his telescope and made his way back to copy his notes in letters to colleagues back home and across Europe. He soon left Lilla Edet, but not yet to return to Cambridge. For the rest of the summer, he had arranged for residency at the Pulkovo Observatory with the eminent astronomer Friedrich Georg Wilhelm von Struve. There he continued his mission to learn the methods, tools, and habits of the great astronomers, while indulging in the many state-of-the-art instruments the well-funded observatory had created. You might expect such devoted astronomers to immediately discuss their observations and impressions from the eclipse, but sky conditions were so good for three weeks, that they had plenty to see and do with each other before a cloudy night prevented any new distraction. The Struve family was eminently gracious with Bond, and after more of an astronomical tour around Europe, he set sail for home at the end of October.

Fig 3 : Daguerreotype of partial solar eclipse of 28 July 1851, HCO, Cambridge, MA.

Meanwhile, back in Cambridge, for the July event, William Cranch Bond worked with the famous daguerreotypist John Adams Whipple to capture images of the partial eclipse (Fig. 3). With the recent development of a successful photographic process by Daguerre in 1839, many scientists, and astronomers especially, realized the potential for a such a static image in making precise observations. Luckily for the Bonds’, Boston was a hub of early photographic activity, with constant innovations made by Whipple and William Draper, father of Henry Draper (for whom HCO embarked on a photographic survey of the sky in the late 1800s). Whipple was interested in photographing the moon and stars, a task he could complete with the help of the Bonds’ and their new 15-inch refractor telescope, installed in 1847. Over the next few years, Whipple and the Bonds’ succeeding in photographing the moon, Jupiter, and star Vega (alpha-Lyrae). George Philips Bond took some of these images with him to the British Exhibition of 1851, where they received “the highest commendations.”

We knew little about the sequence of images Whipple took for the 1851 partial eclipse, until we discovered the record of the activity hidden in an old logbook that was part of our Project PHaEDRA. This remarkable passage lists all those present (including Robert Treat Paine), their duties, and the precise times when each plate was exposed to the light. It was a much more grand undertaking than one man pointing a camera at the telescope eyepiece. Everyone present had a job, whether calling out times, watching the boundaries of the sun for moments of contact, prepping plates, exposing them to the image, or speeding them off into the developing process. Luckily the sky was clear enough in the direction of the sun for there to be something to photograph; elsewhere in the region the partial eclipse, which reached obscuration of around 20%, went totally unnoticed. These images, along with George Phillips Bond’s narrative of his expedition in Sweden were quickly published by the Boston Traveller, to disseminate the observations and experiences to an ever curious public.

Fig 4 : Plate of totality for eclipse of 7 August 1869, Shelbyville, KY. From HCO Plate Stacks.

Over the next few decades, the Observatory refined its photographic processes, along with the rest of the world, to produce images that were more than aesthetic. At HCO, Joseph Winlock and Edward and William Pickering devoted their expeditions to obtaining photographs, and their time planning expeditions to refining the process. Their goal was not to represent the beauty of eclipse, but rather to capture the image as it appeared. With this static record, they could parse through the details after fact, using spectral analysis and various other methods to identify brightness, temperature, composition, etc. But more importantly, they could compare results with other photographs without the interference of the human hand; if the specifications of the camera and telescope were known, as well as the times of exposure, then each image could be reasonably compared with another. In 1869, a total eclipse would cut across North America, the first since the invention of photography, and Joseph Winlock viewed this as the perfect opportunity to demonstrate both the scientific potential of photography as a tool, and the scientific worth of the United States as a nation.

With ample funding from Congress, Winlock arranged an expedition to Shelbyville, KY, close to his childhood home. He was particular concerned with two tasks: photographing the corona such that he could study the spectra of the prominences, and locating an intra-mercurial planet, between Mercury and the Sun. With a cumbersome array of telescopes, cameras, and developing equipment, Winlock’s expedition was both an expensive undertaking, and a local phenomenon. Crowds gathered around the expedition camp to watch the photographic process in action. Winlock’s team, including John Adams Whipple, took photos through the whole event, producing a sequence that documented the movement of the sun. But the most praised images were of totality, which Charles Young called called “the most beautiful record of the inner corona yet obtained.” (Fig. 4).

But Winlock was not aiming for beauty. In fact, for Winlock, the single image of the corona meant very little. Winlock believed that the true scientific value of photography comes from its “repetition and comparability.” The next year, in 1870, he traveled Jerez de la Frontera in Spain to repeat his experiment. Back in Cambridge, William Pickering, brother of the director Edward, was hard at work refining the photographic tools to better capture the data available to the eyes, and even measure phenomena outside of visual observation. He criticised the Shelbyville plates as too “flat,” and looked for a way to better capture the wispy, grand, “visual appearance” of the corona. He participated in many expeditions to photograph eclipses over the next twenty years, but he was not able to satisfactorily translate the fine details of the corona into the photographic image until his expedition to Willows, CA for the eclipse of 1 January 1889 (Fig. 5).

Fig 5 : Plate of totality for eclipse of 1 January 1889, Willows, CA. From HCO Plate Stacks.

The solar eclipse of 28 May 1900 provided another chance for many on the east coast to observe totality. While the shadow would not pass over Boston, the path would be “unusually accessible” from Washington, DC, where another important American observatory could dispatch an expedition. So the Smithsonian Astrophysical Observatory, under the direction of Samuel Pierpont Langley, petitioned Congress to fund for a camp in Wadesboro, North Carolina. In his proposal, Langley laid out the primary objects of the expedition: to closely photograph the inner and outer regions of the corona; to measure the heat and distribution of energy in the corona; and to search for the hypothesized intra-mercurial planet. Langley did not have much hope for this last point, but had reluctantly added it to his plans after being approached by William Pickering, who had designed a special apparatus for the purpose and was requesting as many other observation parties to take a look as well. Langley “had no strong expectation that anything but negative evidence would be secured,” but nevertheless he felt compelled to oblige, perhaps because William’s brother Edward Pickering, then directory of the Harvard College Observatory, had agreed to loan Langley his 8-inch telescope, which would provide the focus needed for the desired close-up shots of the corona. This was not the first instance of cooperation between SAO and HCO, nor would it be the last.

Langley and his crew arrived with their instruments in Wadesboro about two weeks before the eclipse, to set up operations and practice their duties for the short event. They had already undergone one full dress rehearsal in Washington, where they tested and refined their instruments and methods before making the journey out. In Wadesboro, the townspeople graciously welcomed the expedition, and Langley returned their favors with public lectures and night-sky viewing parties, which were always well attended.

The day of the eclipse was cloudless, and the team obtained useful data for all their tasks. Regarding intra-mercurial planets, Langley concluded that there could be nothing brighter than fifth stellar magnitude; optimistically, perhaps as a gesture of goodwill, Langley relates of a few “suspicious objects” found on the plates, but which cannot be verified by other plates. His team had somewhat more success in measuring the heating effect of coronal radiations, which was “recognized and found unexpectedly feeble.” Langley does not interpret this weakness along the dominant paradigm, to mean that coronal matter was at a high temperature, or that it simply reflected sunlight on the instrument’s meter. Rather, in conjunction with observations from other eclipses, Langley postulates that the nature of corona must be either similar to a glow electrical discharge, or the incandescence of particles in proximity to the hot photosphere. Langley favors the former, but calls for more experimentation to determine the real nature of the corona.

Fig 6 : Close-up of the inner corona, eclipse of 28 May 1900, Wadesboro, NC. (SAO)

This SAO expedition had the most success with the photography of the inner corona. With the 135-foot focus lens camera, they obtained five images of different exposures. Langley was particularly entranced by these glass plates: “The originals must be seen to be appreciated for there is no way of reproducing on the printed page what can be seen on looking through a glass negative against a ground-glass surface.” Nevertheless, “where there is so much of interest in the original, a good deal remains in a good reproduction.” This image was given an exposure of 8 seconds at the very end of totality, which gave the clearest picture of solar prominences to date (Fig. 6). With these images, Langley deduced different types of coronal streamers, but he was not sure exactly how to interpret these photographs. At the time, the nature of the corona was so little understood, that, in Langley’s opinion, hypothesizing on its intricate details could only cause further confusion. As astronomers observe more eclipses and come to better understand the nature of the corona, then these images will find their best use as points of reference and comparison.

The late 1800s had been a remarkably prodigious era for eclipses on North American soil, with at least one in every decade. The astronomers at Harvard tended not participate in any major global expeditions, a fact that slightly disappointed Annie Jump Cannon. So, for the first twenty years of the twentieth century, they kept their focus on nocturnal projects (or at the least, daytime computations of the night sky). For the 1923 eclipse, Annie Jump Cannon, the famous computer now in the eminent later stages of her career, travelled out to Catalina Island, California with astronomers from Griffith Observatory in Los Angeles. Unfortunately, the day of the eclipse was heavily overcast, a fact that caught Cannon and the other local astronomers by surprise, because forecasts had been clear in that season for all of living memory. “One does not soon recover from such a shock,” she wrote, but such grand expeditions always run this risk. And Cannon’s cross-country trip was not a waste: she was still able to visit many of the observatories along the west coast, to learn from their methods and practices in the same way that George Phillips Bond did on his tour through Europe.

On 24 January 1925, an eclipse graced the northeast, although totality again avoided the Boston area. Still, the staff at HCO easily prepared expeditions to numerous spots around the region. Annie Jump Cannon took up station in Poughkeepsie, New York, while Edward King and Cecilia Payne joined the team at Maria Mitchell Observatory on Nantucket. With a few other posts in Buffalo and New London, the teams were spread enough to help the odds of finding clear skies. Oddly enough, for a northern January morning, clouds only covered the Buffalo station, where Observatory director Harlow Shapley was prevented from announcing moments of contact over radio. In Nantucket, King and Payne took photographs to measure the total light of the corona, and determine the relative intensity of light distribution in the corona.

In his report on this expedition, King notes how busy all members were with their scientific business during the event. Since they knew beforehand of all of their tasks to do in such brief period, the observers planned and practiced their actions precisely, so that “all engaged had, as a reward of quick action, at least a brief view.” And in this moment, they took the chance to digest the spectacle. Annie Cannon noted that “the mystical shadow bands danced over the snowfields, glowing prominences streamed out, and the corona flashed forth its matchless beauty.”

Fig 7 : Journal of Annie Jump Cannon for eclipse of 28 May 1900, Virginia Beach, VA. From Harvard University Archives (HUGFP 125).

Cannon was a particularly poetic observer. In a short diary kept during her observations of the 1900 eclipse on Virginia Beach, VA, she describes how she turned away from the sun, and faced the coming shadow (Fig 7):

“The rolling darkness was unlike anything I have ever seen. It did not seem like the coming of night on the beach. It was more like the gathering of a mighty storm. The effect on the harbor, on a wooded promontory, and on Hampton Roads in the distance was weird and unnatural. Below us, we are told birds sing at their nests, and the chickens wander to roost. The air grew colder, the fall in the temperature was said to be slight, but I experienced a very chilly sensation as totality approached. This may have been to mental rather than physical conditions. The great shadow was coming with enormous speed from the west.

 

Under the falls of Niagara, on the top of Vesuvius, had before seemed to me to be the times of my life when I was nearest to the forces of nature. But those experiences were nothing to this…When totality was called, we faced the east. The supreme moment had come. The grandeur and yet the awfulness of that vision cannot be described. A friend aptly remarked “It was like the hand of God raised in mid-air.” We had about 100 seconds of totality to see so much. The pearly corona, the planet Mercury, flames colored near the sun –”

She invokes the spirits of Copernicus, Tycho Brahe, and all other great human minds who managed to figure out and predict such an awesome and terrible event. The science of the event, of course, was important to Cannon, but the experience was paramount. Following the eclipse, her team had agreed to a 10 minute silent period to reflect on and record their observations. Nobody found this difficult.

Fig 8 : Photo of eclipse camp for eclipse of 31 August 1932, Gray, ME. From Harvard University Archives (HUGFP 125).

The eclipse of 31 August 1932 gave the HCO another convenient opportunity to send out a small scale expedition, this time to Gray, Maine. Again, given the haphazard historical forecasts in the region, the expedition planners carefully considered various campsites. Eclipse enthusiasts had identified cumulous clouds as the biggest risk to the observations, and to best avoid these cloudy skies, Fred Whipple, leading the expedition from HCO, worked along with the Department of Meteorology at Harvard to survey various sites near lakes and behind hills. After finding a suitable farmstead outside of the small town of Gray, Whipple asked the landowner if he could verify his meteorological calculations. A bit reserved and intimidated by such an opaque question, the farmer responded with observations of how storms would split over the lake when coming from the west. Whipple seemed confident enough that this would guarantee a clear sky, a prediction which was happily verified on the day. A small crowd gathered around the expedition camp to watch the spectacle (Fig. 8). In all, the team obtained many positive results about the scattering and polarization of the corona, including many clear photographs at different wavelengths. But for Whipple, one of the most valuable lessons learned was this: “two and a half days is the minimum possible time in which to install the equipment to be used for observation at a medium-sized eclipse camp.”

As part of this expedition, young Donald Menzel, only just hired at the observatory, offered his expertise on the solar chromosphere. Over the next few decades, Menzel made a name for himself at the observatory by being the go-to source on all things solar. He even served as the director of the observatory from 1952-1966. Eclipses were one of his favorite events, and he travelled all around the world to witness them. After his retirement, he still led expeditions where he would focus on the public dimensions, offering lectures and viewing parties to all in attendance. His final expedition was a grand one. In partnership with MIT and National geographic, Menzel headed a team to Mauritania in Africa to study an eclipse with totality upwards of seven minutes. He spent most of his time teaching local children about the coming event, and when the time came, he made sure to take off his glasses for a good view (Fig 9).

Fig 9 : Photo of Donald Menzel with eclipse of 30 June 1973, Mauritania, Africa. From MIT Collections.

Meanwhile, back at the ranch in Cambridge, without totality, eclipse observations have never been so spectacular as these expeditions. But this has never discouraged any of our homestuck astronomers. For the partial eclipse of 13 December 1974, Steve O’Meara and Pete Collins held a viewing party on Observatory Hill, where they set up telescopes and did solar photography. In the logbook for this day, O’Meara exclaims, “solar eclipse day, … and not a cloud in the sky! Turnout: big success, loads of people.” Even though the total maximum coverage of the sun only reached around 70%, O’Meara still showed the guests sunspots and lunar mountains, while explaining the shadow bands and peculiar pin-hole effect of the leaves.

On 21 August 2017, Cambridge again will experience coverage of around 65%. Be sure to look up (with glasses of course), and down at the shadows of the trees for a special sight! And once you’ve been psyched up by the event, come into the Wolbach Library and relive the experience through these artifacts of Harvard and Smithsonian’s eclipse expeditions.

 

 


Bibliography

Archival Collections

Annie Jump Cannon Papers. Harvard University Archives (HUGFP 125).

Donald Menzel Papers. Harvard University Archives (HUG 4567).

Harlow Shapley Papers. Harvard University Archives (HUG 4773.xxx).

Harvard College Observatory observations, logs, instrument readings, and calculations (Project PHaEDRA). Wolbach Archives, Wolbach Library, Harvard University (KG11365-6).

Papers of George Phillips Bond, 1851-1865 (inclusive). Harvard University Archives (HUG 1224). (Digitized Copy)

Published Sources

Andrews, L. B. & Whipple, F. L. (1932) “The Harvard eclipse expedition of 1932.” Popular Astronomy, Vol. 40, p.530.

Bailey, S. I. The History and Work of Harvard Observatory, 1839 to 1927 : An Outline of the Origin, Development, and Researches of the Astronomical Observatory of Harvard College Together with Brief Biographies of Its Leading Members. Harvard Observatory Monographs ; No. 4. New York ; London: McGraw-Hill Book. (1931).

Bond, G.P. “Solar Eclipse of July 28, 1851.” Astronomical Journal, Vol. 2, Iss. 31. (October 22, 1851).

Cannon, A.J. “Astronomical Adventures.” The Radcliffe Quarterly. Cambridge, Mass.: Radcliffe College. (April 1931).

Cottam, S. & Orchiston, W. Eclipses, Transits, and Comets of the Nineteenth Century: How America’s Perception of the Skies Changed. Springer: New York. (2015).

Gingerich, O., and Hoskin, M. A. Two Astronomical Anniversaries : HCO & SAO. In Journal for the History of Astronomy ; v. 21, Pt. 1. Cambridge, Mass.: Harvard-Smithsonian Center for Astrophysics (1990).

Harvard College Observatory. Annals of the Astronomical Observatory of Harvard College. Vol. 8, 1876.

Hoel, A.S. “Measuring the Heavens: Charles S. Peirce and Astronomical Photography.” History of Photography, 40:1: 49-66. (2016).

Jones, B. Z., and Boyd, L. G. The Harvard College Observatory: The First Four Directorships, 1839-1919. Cambridge: Belknap Press of Harvard University Press. (1971).

King, E.  “Harvard Eclipse Observations on January 24, 1925.” Popular Astronomy, Vol. 33, No. 5. (May 1925).

Langley, S. P., and Abbot, C. G. The 1900 Solar Eclipse Expedition of the Astrophysical Observatory of the Smithsonian Institution. Publication (Smithsonian Institution) ; 1439. Washington: G.P.O. (1904).

“Robert Treat Paine: Obituary.” Proceedings of the American Academy of Arts and Sciences, Vol. 21. (May, 1885 – May, 1886).

Shapley, H. “Annual Report to the director of Harvard College Observatory.” No. 80. (1925).

— — — — — . “Annual Report to the director of Harvard College Observatory.” No. 87. (1932).

Alex McGrath

Archives Assistant at Wolbach Library
Alex is the Archival Assistant at Wolbach.