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Home , Antikythera mechanism, Aratus, Celestial globe, Farnese Atlas, Globe, Planetarium

The magic of the Atwood Sphere

Exactly a century ago, on June Dr. Jean-Michel Faidit 5, 1913, a “ demon- Astronomical Society of France stration” by Professor Wallace W. Montpellier, France Atwood thrilled the populace of [email protected] Chicago. This , built to ac- commodate a dozen spectators, took up a concept popular in the eigh- teenth century: that of turning stel- lariums. The impact was consider- able. It sparked the genesis of modern , leading 10 years lat- er to an invention by Bauersfeld, engineer of the Zeiss Company, the Deutsche in .

Since ancient times, mankind has sought to represent the sky and the . Two trends emerged. First, stars and were easy, especially drawn on or . This was the case, for example, in Egypt with the of Dendera or in the Greco-Ro- man with the statue of support- ing the sky, like that of the at the National Archaeological Museum of Na- ples. But things were more complicated when it came to include the , , , and their apparent motions. Ingenious mecha- nisms were developed early as the Antiky- thera mechanism, found at the bottom of the Aegean Sea in 1900 and currently an exhibi- tion until July at the Conservatoire National des Arts et Métiers in . During two millennia, the human mind and ingenuity worked constantly develop- ing and combining these two approaches us- ing a variety of media: , quadrants, armillary spheres, astronomical clocks, co- pernican and celestial globes, cul- minating with the famous Coronelli globes offered to Louis XIV. In 2006 they were ex- hibited at the National Library of France. Diagram of the Atwood Sphere from 1913. One place this diagram appeared was in Popular Science Monthly, the precursor to Popular Science, Volume 84, 1914. Creative Commons. archive.org/details/ (Continues on Page 12) popularsciencemo84newyuoft 10 Planetarian June 2013 As the venerable device celebrates its 100th birthday, two authors take a look at where it fits in the evolutionary history of planetariums

Dr. Marvin Bolt When considering cutting-edge Vice President for Collections technology from a century ago, one Adler might reasonably expect it either Chicago, Illinois USA to be obsolete (say, Formica) or to [email protected] be still used with little change (such as the zipper or windshield wipers). Rare indeed is the object that is both obsolete and yet still used with lit- tle change, but the Atwood Sphere is one. Its allure makes it unusual and unique among the inventions of 1913.

What is the Atwood Sphere? The Atwood Sphere is a 17-ft-diameter stain- less steel sphere punctured by 692 holes of dif- ferent sizes that the . It opened to great acclaim at Chicago’s Academy of Sci- ences on June 5, 1913. Built for the impressive sum of $10,000, de- signer Wallace Atwood wowed his audiences that evening, and for several years to come, by demonstrating the visible motions of the night sky. The 500 lb. metal , being only 1/64th in. thick, bowed and flexed as it rotated, so that visitors could also hear it and imagine the music of the heavenly spheres. Hearing sto- ries illustrated with constellations drawn on the interior surface, accompanied by glow- ing disks to represent planets and a moveable light providing solar illumination, children and adults alike were enthralled by the wonders of the heavens. When the opened just a few miles away from the Atwood in 1930, the Atwood was considered obsolete, and never regained its popularity at the Acad- emy. Indeed, it was not used at all for some years in the 1930s, although in 1941 it was used to teach navigation principles to the US Na- The Atwood Sphere today, Courtesy Adler Planetarium. (Continues on Page 13)

June 2013 Planetarian 11 (Faidit, continued from Page 10) World War, with the progress of the construc- tion of metal structures. Buckminster Fuller Early 17th and 18th centuries went on to develop the principles of the ar- Now became the problem of represent- chitecture of geodesic , and this form ing a globe’s sky. In the Arab world and , was consecrated by the Géode at La Villette, some arches in luxurious palace were deco- rated with diamonds. Lit with candles, they designed by the French architect Adrien Fain- allowed the viewer to enjoy a sparkling “- silber in 1983 at the time of the project for the ry” sky, but the image was fixed. bicentennial of Boullée. The Géode is located This changed in the seventeenth centu- at Cité des Sciences et de l‘Industrie in Paris. ry with the invention of the Gottorp Globe. With a diameter of 3.1 meters, it was designed Temple to , Lequeu (1790) by Adam Olearius at the behest of the Duke A few years after Boullée’s design, to cele- of Holstein-Gottorp and built by Andreas brate the Revolution, Jean-Jacques Lequeu, a Busch of Limberg between 1654 and 1664. cartographer by profession, an unknown art- Painted on the outside with continents and ist and an enthusiast, imagined oceans known at the time, it is tilted 54 de- the Temple to the Earth with the same star- grees. ry sphere, adding an educational aspect with An entry in the Indian Ocean allowed a globe Earth at the center, as the Stellarium spectators inside, where they could see con- Weigel in . stellations painted on the interior and lit by Again, the project remains only in the state holes for the stars appear. An operator was to of diagram, but it marks a theoretical result manually rotate the sphere. showing the architectural progress of the Tsar Peter the Great received the globe as time. a present in 1715 and it was installed at the The nineteenth century saw the develop- Academy of Sciences in St. Petersburg. De- ment of panoramas, the ancestors of cinema, stroyed by fire in 1747, it is completely rebuilt as illustrated by Daguerre‘s Diorama and other between 1748 and 1752 and is now preserved theater devices. They bloomed in large cities at Lomonosov Museum. and included shows dedicated to starry sky. Alongside this first stellarium, was anoth- At the threshold of the twentieth century, er world designed by Erhard Weigel, profes- in 1902, George Méliès’ production A Trip to sor of mathematics at Jena between 1654 and the Moon (Le Voyage dans la lune) reflects the 1699. This globe, at a diameter of 11 feet, is a lit- public‘s enthusiasm for astronomical events tle more involved with an earthly sphere in- stalled in the center. Professor Atwood’s Sphere, 1913 In the early eighteenth century, Roger Long, Tonight is June 5, 1913. People flock to Mu- professor of astronomy at Cambridge, made seum of the Academy of Sciences of Chica- another mobile globe that was kept at Cam- go for the opening of a large rotating celestial bridge’s Pembroke College in 1758. Named sphere. Professor Wallace Atwood, director Uranium, it had a diameter of 18 feet and of the museum, its designer, is in charge. The could accommodate 30 people. Its complicat- door closes, and viewers see a beautiful star- ed rotation was accomplished with ropes. De- ry night. Slowly, familiar constellations rise in From top: The Gottorp Globe from 1664, Eise spite the enthusiasm of Long, his Uranium did the east, while others plunge to the west. With Elsinga’s planetarium from 1781, and the con- not receive the expected popular welcome. cept for Boullée’s Newton Memorial. All imag- suitable projectors, it is the moon and planets’ es on these two pages Wikimedia Commons. turn to be on stage. And then the sun, repre- Architecture takes over sented by a small flashlight, the stars Mobility being an obstacle, the stellarium and Maupertuis, was used to calculate the re- to simulate the arrival of the day. The enthu- concept was kept alive by the architects of the turn of Halley‘s in 1759 and paved the siastic shouts echo in the museum. eighteenth century. A current against the Ba- way for celestial mechanics. This 4.57-m sphere consists of sheets of gal- roque and classical style that reigned, the ar- Boullée was born in 1728, the year follow- vanized sheet iron of 0.4 mm thickness, suit- chitects proposed bold figures where the ge- ing Newton’s death. His concept was great. It ably curved. Weighing 227 kg, it is inclined at ometry was at the service of creativity. The obeys the geometry of a pyramid face, insert- 42 °, corresponding to the latitude of Chicago, spherical shape was directly interested in as- able into a triangle, and incorporates the fas- and rests on three that permit its rota- tronomy. This was particularly the case in the cination with spheres, a trendy artistic theme tional movement. An electric motor actuates Cenotaph for Newton, designed in 1784 by following the launch of the first balloon flight the two lower wheels. Étienne-Louis Boullée as a perspective on the in 1783 by the Montgolfier brothers. Small perforations in the outer skin form centenary of universal gravitation. Although Boullée’s vision was a huge sphere with a 692 pinhole stars visible to the naked eye. The it was never built, Boullée was the first archi- cylindrical drum base with an opening that moon is made ​​by a series of small disks coated tect to design such a permanent building with allows the entire sphere to be seen. Beyond with a light coating, corresponding to the dif- bright stars and the effect of day and night. the imposing appearance, the most spectacu- ferent phases, while the planets Venus, Mars, Boullée devised his cenotaph, or an “empty lar concept was inside with a representation Jupiter and Saturn are also figured with their tomb” to honor remains interred elsewhere, of the sky. changing positions. during the period of time when science was Long considered an impossible dream, Initiated by the president of the Academy flowering. The theory of universal gravita- the hollow sphere designed by Boullée ex- of Sciences, La Verne W. Noyes, the sphere is tion, spread throughout France by Voltaire perienced renewed interest after the Second (Continues on Page 14)

12 Planetarian June 2013 (Bolt, continued from Page 11) dieval and later audiences. The use of the word planetarium itself val Reserve unit at Northwestern University. most likely derives from the device made in Approximately 900 men passed through the the mid-1300s by Giovanni de’ Dondi, or rath- school every three . er from his text describing his machine. Like Over time, the instrument itself suffered many instruments of this kind from the late some decay. Being labeled a “white elephant” and later, it displayed the loca- by the media in 1956 did not help matters. tions of the seven classical “planets”—Mer- With little attendance and dwindling respect cury, Venus, sun, moon, Mars, Jupiter, and for it, the Atwood eventually suffered the in- Saturn—on dials or faces of a clock. In this in- dignity of being completely brought down to stance, the device had seven different “clock” Earth; its exterior was plastered and painted faces, one for each then known. to simulate a terrestrial globe in 1959. It was This kind of object—with faces or dials using given a new name as well: “The Globe-Plane- a pointer of some kind to indicate positions— tarium.” fits the broader category of mechanical de- The name changed again in 1983 to the “At- vices leading to the modern planetarium. wood Celestial Sphere,” but even so, it was These planetary took on a differ- not used from the early 1960s until 1986. ent form after the Copernican revolution in The sphere’s big move the sixteenth and seventeenth centuries, with various geared devices teaching the new as- In 1995, the Atwood left the Academy when tronomy of planets orbiting the sun. it was donated to the Adler Planetarium. The After Newton provided an intellectual- entire globe was dismantled—its wood inte- ly compelling explanation of the Copernican rior taken apart and the sphere itself cut into system, the public appetite for it led to a new 6 pieces—and put into storage. In the fall of material culture. Around 1705, George Gra- 1996, the Adler began planning its restora- ham built the first mechanical model of the tion, and completed that task in 1999 in the sun-Earth-moon system; this device is now significantly expanded Adler facility that add- part of the collection at the Adler Planetari- ed 50% to its exhibit space as well as a new um. state-of-the-art digital theater. Artisans produced many more such table- Today, ironically, the Atwood is located top models in the following centuries, there- just a few steps away from the world’s most by disseminating astronomical knowledge to technologically-advanced planetarium sys- a wider public audience eager to own this tem; just as ironically, it again enjoys a level universal knowledge. These are frequently of attendance and popularity it did a centu- known as orreries, named after the Fourth Earl ry ago. Understanding why takes us on a his- of , who commissioned a device similar torical tour of how we have built devices that to Graham’s. demonstrate the wonders of the cosmos.

Mechanical planetariums before Globes before Atwood Atwood Alongside the mechanical planetarium his- tory, we find another tradition that eventually Throughout history, astronomy has enjoyed produced the Atwood. This genealogy chron- a high reputation, due to its cosmic scope and icles spherical models of the heavens, usual- the universal belief in the powerful, yet mys- ly portraying the distribution of the stars, but terious connections between heaven and From top: The Mechanism, the not the motions of the planets. earth. Every known culture has its own astro- Coronelli Globe at the National Library of The earliest reference to a nomically-informed myths of origins, asso- France, and A Philosopher Lecturing on the Orrery dates from about 370 BC, when Eudoxus ei- ciated rituals of meaning, and some material by Joseph Wright of Derby at the Derby Muse- ther made one or brought one from Egypt, manifestations that express them. um and Art Gallery, England. while the oldest surviving celestial globe is Around the world, we know of altars, tem- the Farnese Atlas, circa AD 150, now in . ples, homes, cities, and other spaces designed lennium. Reports of various devices in Asia Other records indicate the existence of Islam- to mirror on earth the structure and motions merit more investigation, as the most well-re- ic celestial globes from the 9th century, with of the heavens. searched sources address the European set- the oldest surviving example from the late The most specialized imitations find ex- ting. There, the invention of the clock soon 11th century. pression in mechanical systems that closely led to devices that displayed the changing po- European globes are known circa 1300, al- mimic the movements and timings of specif- sitions of key, selected heavenly bodies. though the oldest survivor dates more than a ic heavenly bodies. Indeed, the oldest known These astronomical clocks were found century later. Since 1500, celestial globes, al- mechanical device of any kind is the Antiky- in public spaces, such as town squares or in most always in tandem with terrestrial globes, thera Mechanism, an extraordinary instrument churches, or in private collections. While their summarized what was known of the heavens made 2000 years ago and found just a century key informational feature was a dial face with and the Earth. ago in a shipwreck. While scholars still debate a pointer indicating the current location of Along with these globes, armillary spheres its complex details, all agree on its fundamen- the specified object, the demonstration of provided an effective way to teach the mo- tal astronomical purpose. regularity and predictability manifested di- tions of the heavens. Since 1400, armillary We know of very few physical or mechani- vine order, which was the underlying message cal models of the heavens during the next mil- to be disseminated and to be absorbed by me- (Continues on Page 15)

June 2013 Planetarian 13 ly small initiative will ium in 1913 was the fusion between these two lead to a quantum leap previously separate representations of stars that will revolutionize and planets. the history of represen- Larger projects were born from a meeting tations of the sky. between several actors. In the months fol- lowing the entry into service of the Atwood The planetary Sphere in Chicago, the founder and first direc- mechanisms tor of the Deutsche Museum, Oskar von Mill- As with the represen- er, entered into a relationship with , tation of stars with stel- director of the of Heidelberg, lariums, modeling the and Walter Bauersfeld, engineer from the also has ex- Zeiss Company. Starting in July 1913, the idea perienced several cen- emerged to take the rotating sphere to high- turies of development. er dimensions and incorporate the planetary Museum collections movements. are full of these orreries, Delayed by the war, Bauersfeld’s concept which set the planets in still faces technical difficulties to achieve a ro- motion around the sun tating sphere of 6 meters. Starting in March with mech- 1919, he reworked the initial idea and came up anisms, both through with a large fixed sphere with a central projec- horizontal devices and tor to show both moving images of the night vertical, integrated as- sky as well as the sun, moon and planets. tronomical clocks. As- A first design of this new projector mount- tronomical clocks mul- ed at the center of the sphere appears in his tiply after the lead of the notebooks in May, 1920. Developed over the by Giovan- next three years, it is first demonstrated in Au- ni Dondi, developed be- gust, 1923 in Jena, under a 16-m special- tween 1348 and 1364. ly fitted on the roofs of the Zeiss Company. The particular case of It was demonstrated in October that year in the moon leads to tel- Munchen under a 9.8-m dome, before coming luriums and lunariums, back to Jena. allowing the represen- There, the design was improved with the tation of eclipses, while help of Walter Villiger, who developed its ed- from the eighteenth ucational functions, and finally, in May 1925, century on, spurred by the new planetarium was installed at the the return of Halley‘s Deutsche Museum in Munich and open to the comet, another device public. modeled the elliptical During the interwar period, planetariums planetary movements multiply rapidly in the world, particularly of , a cométari- in large cities in Germany and mostly in the um. domes of large diameters. There were 25 erect- The 1766 painting A ed by 1939, including 11 in Germany and five Philosopher Lecturing in the United States. on the Orrery by Joseph America‘s first planetarium was built in Wright, housed in the Chicago in 1930 at the Adler Museum, evok- Top: Dr. Wallace W. Atwood inside the Atwood Celestial Sphere at the Academy of Sciences of Chicago. Below: the sphere, exterior front with Derby Museum (United ing in its architecture Boullée Cenotaph for lower exhibits, Laflin Building, circa 1920s. From the collection of the Kingdom), illustrates the Newton. Chicago Academy of Sciences, used with permission. success of these minia- Paris was no exception, with the first plan- ture planets. etarium built for the six months of Expo 1937 (Faidit, continued from Page 12) Larger projects began and coordinated by Reysa Bernson. But it was completely renovated in 1959. The exterior emerging, such as the well-known global built after the Second World War, and especial- is painted to present a geophysical globe and by Eise Eisinga at his home in Franecker (Hol- ly during the exploration of the moon, that colored filters are installed for the brightest land, 1774-1781; see Planetarian, 40-4, Decem- planetariums saw their highest development, stars. Ultraviolet lamps simulate dawn and ber 2011). Updated with electricity in 1925, the built by the hundreds in the United States, Eu- dusk. And a horizon is added: a skyline of the Copernican planetary at the Deutsche Muse- rope and Asia, mainly . skyscrapers of Chicago. um, Munich, marked a climax in this represen- tation of the solar system’s precision, but with In conclusion. Stellarium reborn the disadvantage of a single viewer placed in The year 1913 is, therefore, a major turning The impact of this remarkable stellarium a rotating cage. The instrument was partially point in the history of representations of the rapidly raises identical projects, particular- destroyed by bombing during the war. sky. The entry into service of the first mod- ly in Germany. In 1914, another stellarium is ern planetarium that merged the approach of built in Heilbronn by Robert Mayer, while the 1913-23: Genesis of planetariums stellariums with Copernican orreries had a re- Deutsches Museum in Munich began study- But the most important consequence re- sounding impact. The advent of planetariums ing a comparable installation. This seeming- sulting from the impact of the Atwood stellar- (Continues on Page 16)

14 Planetarian June 2013 (Bolt, continued from Page 13) spheres became a standard tool for teaching astronomy to students. For present purposes, what distinguishes the mechanical tradition from the globe tra- dition is that the former point out locations in the sky, whereas the latter address the ap- pearances in the sky. That is, the mechanical devices indicate, for example, that the sun is currently located in the . Right: Dr. William J. Beech- This knowledge could be put to use for vari- er, director of the Chica- go Academy of Sciences, in ous computational, astrological, or even med- the foreground and Thurston ical purposes. Wright, preparator, in the While one could, and many did, put globes background, circa 1959, with to a similar use, the globe and armillary also the sphere transformed into provided explanations of what appeared in the Globe-Planetarium. From the collection of the Chica- the sky, for example, providing a way to un- go Academy of Sciences, used derstand how the sun’s location in Aries made with permission. Below: The the other constellations appear (or disappear) Atwood Sphere in use today in the night sky, why the moon appeared in at the Adler Planetarium. Pho- to courtesy the Adler. different phases in various constellations over the , and more.

The Copernican shift The adoption of the Copernican system marked a significant moment in these two tra- ditions. A model of how the sky appears did not need to show the reality of the solar sys- tem; just as significantly, indeed even more significant from an economic standpoint, the model of reality became distinct from how the sky appeared. The 17th and 18th centuries saw the contin- ued production of mechanical devices with dials that showed the Copernican reality with no attention to what appeared in the sky. The Graham orrery was followed by a variety of gadgets: pocket orreries, without which no gentleman would be caught, and grand orre- ries, whose enchantment was captured best by Joseph Wright of Derby. Other devices, sometimes called Coper- nican moving spheres, retained the look and feel of armillary spheres but instead of teach- ing about what appeared in the sky, they illus- trated a God’s eye view of planetary orbits.

A new kind of globe It is one thing to explain the heavens; it’s quite another to offer a simulated experience fire in 1747. How much survived is unclear, but tronomy, combined these two techniques in of them. A large celestial globe, made in 1654- seven years later, a new globe, now known as his 17 ft. globe at Pembroke College in 1758. 66 in Gottorp (Gettorf), near what is now the the Great Academic Globe, engaged audienc- Originally, a lamp illuminated the constella- German-Danish border, did just that. Made es again. tions, although after 1764, newly-bored holes of 7000 lb. of copper and measuring 11 ft. in After several moves and restorations, it is allowed up to 30 visitors to see stars illumi- diameter, it included a small door near the once again open to the public, now at the Lo- nated from the outside. A photograph from South Pole to provide access to the interior. monosov Museum in St. Petersburg. 1874 provides evidence of this sphere, which About a dozen people equipped with oil A related experience was provided by a was demolished and sold for scrap, but the lamps could see gilded stars and constella- much smaller, 20-in. sphere built at the Univer- key inspiration for the Atwood had arrived. tions portrayed on the globe’s interior, and sity of Jena in 1654. This globe displayed stars watch them rise and set against the artificial as tiny holes punched in the globe. The recent- Synthesizing these efforts horizon as the sphere turned about them. ly reopened Mathematisch Physicalischer Sa- Numerous other ingenious planetarium de- After liberating it from its original home, lon in Dresden, Germany features one of these vices merit more attention that the current Peter the Great moved it to the St. Petersburg globes made by Erhard Weigel. space allows, but the final one mentioned Academy of Sciences, where it burned in a Roger Long, a Cambridge Professor of As- (Continues on Page 16)

June 2013 Planetarian 15 (Bolt, continued from Page 16) here must be the hybrid system created at iting the Atwood in the soon-to-be-expanded the Deutsches Museum in Munich, one that Adler facility. Preparatory work involved the attempted to combine the mechanical mod- removal of paint and putty (from its terres- el tradition with globe tradition that simulat- trial incarnation) using scrapers, grinders, and ed the appearances. even acid treatments before hammering the In the early decades of the 1900s, Carl Zeiss mountains back down again. tasked its engineers to develop innovative These efforts plugged many star holes, re- ways for public astronomy. Early approach- quiring their re-drilling. In its original installa- es involved the same technique used by Long tion visitors had to walk up a flight of stairs and Atwood; Max Wolf had sketched out such to enter the sphere, while we deemed it im- a plan in 1912 prior to his receiving a printed portant to provide universal access. This re- description of the Atwood and forwarding it quired designing a carriage moved by a 21 ft. to his German colleagues. long screw built by a company that designed But Zeiss also built the largest mechanical the mass production facilities at the Saturn orrery in the 1920s in Munich. In a 36-ft. cy- car company. This provided a nice cosmic co- lindrical room, elliptical rails hanging from the incidence, not only because of the name but 9-ft ceiling used electric motors to drive the also because the assembly line mass produc- planets, represented by poles with light bulbs. tion of cars was another one of those innova- The central sun illuminated the planets and tions from 1913. The Zeiss Mark 1. Wikimedia Commons their movements, modeled on a of 12 Today’s tour guides take up to 8 visitors at minutes per terrestrial year. time into the Atwood, where they can watch (Faidit, continued from Page 14) The key feature was a small platform linked the stars, illuminated from outside, rotating is so tied to 1923 and Bauersfeld that the fact to the Earth; it carried visitors and a periscope with diurnal motion. Fluorescent tubes light that the genesis of the idea actually started in through which one could watch planetary and up otherwise invisible paint to illustrate the 1913 is hidden. stellar motions. The cumbersome of constellations. Young children, teens, and This story of stellariums is an essential the room-sized orrery, the noise it produced, adults alike leave with a smile on their face, chapter opening the advent of planetariums. and the lack of a convincing experience of the charmed by the simplicity of the experience, With digital technologies, their evolution sky soon led Zeiss to develop optical projec- the solid basic content, and the charming anti- continues today to immersive rooms to sim- tors that convey these appearances more ef- quated technology that creates the Atwood’s ulate space travel. fectively. night sky. The Atwood represents the culmination of Bibliography The current Atwood many centuries of efforts to portray the won- Books: I suppose that one of the reasons why I am ders of the heavens in a controlled environ- Hagar, Charles, Planetarium: Windows to the especially fond of the Atwood Sphere is that ment. It played an important role in motivating Universe. Zeiss, 1980. it was my first project when I started working the development of modern planetarium pro- King, Henry C. and John R. Millburn, Geared at the Adler in 1996. That fall, the Adler be- jection systems, and was rendered obsolete to the Stars. Toronto: University of Toron- gan a carefully-planned restoration for exhib- by it. Yet, visitors today still love it! I to Press, 1957. Marché II, Jordan D, Theaters of Time and Space: American Planetaria, 1930-1970. Rut- gers University Press, 2005. Meier, Ludwig, Der Himmel Auf Erden: Die Welt der Planetarien. Johann Ambrosius Barth, Leipzig, Heidelberg, 1992. Werner, Helmut, From the Globe to the Zeiss Planetarium. Gustav Fischer Verlag, Stuttgart, 1959. Articles: Atwood, Wallace, “The celestial sphere,” Bulletin of the Chicago Academy, No. 2, May 1913, 12. Bauersfeld, Walter, “Das Projektions-Plane- tarium of Deutsches Museum in Munich,” Zeitschrift für Feinmechanik und Precision 32 (1924A), 203-208, 68 (1924b), 793-797. Faidit, Jean-Michel, “Spheres and Starry Tem- ples in the Enlightenment: Boullée Newton Cenotaph, Architectural Precursor to Plan- etaria?” Planetarian 32, 4 (December 2003). Other: Fracek, Elizabeth, Remembering the Atwood Sphere, 365 days of Astronomy, 13 Janu- ary 2010. cosmoquest.org/blog/365daysofa stronomy/2010/01/13 I

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