1Writing at the beginning of the twentieth century, the American astronomer Simon Newcomb reflected on the changes in attitudes towards instrumental error that had taken place in the preceding century:
Contemporaneous with the accession of Pond to the Directorship of the Greenwich Observatory was the foundation by Friedrich Wilhelm Bessel of the German school of practical astronomy. The fundamental idea of this school in the trial of its instrument reverses the maxim of English criminal law. The instrument is indicted as it were for every possible fault, and is not exonerated till it has proved itself correct in every point. (Newcomb, 1906, p. 343)
2Newcomb’s description transforms the roles of individuals within observatories. The astronomers declare the instruments criminals, and directors of observatories instruct their assistants to collect evidence against the instruments. Thereby, the astronomers become the judges, while the assistants become the detectives. Chasing the faults of instruments becomes a Holmesian detective work. As part of this transformation, the main tool of the astronomical detectives was mathematics (Aubin, 2017). Astronomers used mathematics to translate the testimonies of the different instruments into a common language, thereby connecting the different pieces of the instrumental assemblage together like a puzzle. The final published results of astronomical observations made with the instruments were reports of detective investigations. Based on the crimes the instruments were accused of, the astronomical judges sentenced instruments to corrections and disciplining. But how were instruments be corrected and disciplined? Were they punished by inflicting alterations on their bodies (Schaffer, 2012)? Or were they sentenced to constant surveillance in well-guarded astronomical panopticons (Schaffer, 1988)? As this paper demonstrates, the major transformation taking place during the nineteenth century was a shift away from the corporal punishment of instruments to their surveillance-based behaviour control. This shift reflected the increased preoccupation of the astronomers with the mathematical indictment of the instruments on paper by ink, and the increased reliance on division of labour at observatories (Hoffman, 2007).
3From this reframing of astronomers’ engagements with instruments emerges another conceptual transformation: the instrument’s mutation from an inanimate lump of materials into an animated machine (Tresch, 2012). In Newcomb’s characterisation, the astronomical instruments were not seen as separate tools or extensions of the observer’s senses, but rather, as animated independent entities that constantly broke the laws and rules set out by the astronomers. Although both the instruments and the observers were indicted at the same time, they were indicted separately (Canales, 2009). It was only as animated entities that instruments could be charged with committing criminal acts. As a result, astronomical instruments were placed within the same system of surveillance as the observers were. This article argues that if the personal equation measured and disciplined the observer’s character, then the mathematical measurement of instrumental error disciplined an astronomical instrument. Additionally, Newcomb’s criminalisation of the instruments also anthropomorphised them. This framing of instruments contradicts the current scholarship on nineteenth-century astronomical instruments, which argues that the observers were reduced to instruments by their perceptions being calibrated the same way as the instruments (Smith, 1991; Ashworth, 1991; Daston, 2018). Instead, this article reverses this picture by elevating the instrument into what Tresch characterised as the romantic machine: an animated extension of the human senses requiring discipline that formed a machinic assemblage (Tresch, 2012, p. 81). Therefore, Newcomb’s account creates a tension between the humanisation of the machine and the mechanisation of human vision.
4The aim of this paper is to explore two subjects: the criminalisation of instruments, and the transformation of astronomical practices into detective work during the nineteenth century. It takes as its case study the use of the Airy Transit Circle at the Royal Observatory, Greenwich. The instrument was named after its designer, the seventh Astronomer Royal and director of the same observatory, George Biddell Airy. The use of the instrument lasted more than a century. It gained further fame in the 1880s when it was recommended as the instrument to define the Prime Meridian of the World. Its installation in 1850 formed part of Airy’s re-instrumentation programme at the Observatory (Satterthwaite, 2001). The instruments installed manifested what historians interpret as the transformation of the observatory into a factory. Unsurprisingly, Simon Newcomb expressed a similar sentiment:
Before [Airy’s] time the trained astronomer worked with instruments of very delicate construction, so that skill in handling them was one of the requisites of an observer. Airy made them in the likeness of heavy machinery, which could suffer no injury from a blow of the head of a careless observer. Strong and simple, they rarely got out of order. It is said that an assistant who showed a visiting astronomer the transit circle some times [sic] hit it a good slap to show how solid it was. (Newcomb, 1903, p. 288-289)
5Newcomb’s recollections of the instrument raise the following question: did the sturdiness of the instrument reflect its disciplined and animated character?
6What made these instruments animated criminals? As Newcomb argued, during the first half of the nineteenth century, the German school of astronomy (led by Friedrich Bessel) began emerging as a dominant approach within the field. Accounting for instrumental errors within astronomical observations was not a new approach. Historical meridian marks are reminders that collimation errors have been accounted for since the installation of meridian instruments on site. The German school changed the way in which the instruments were “trialled”. As part of the new approach, instruments were always seen as prone to err (or to commit a crime), even after they left the workshops of the most eminent instrument makers. By being aware of this imperfectness, there was an increased emphasis placed on the astronomer’s responsibility to correct the instrumental errors. As Bessel put it:
Every instrument […] is made twice, once in the workshop of the artisan, in brass and steel, and then again by the astronomer on paper, by means of the list of necessary corrections which he derives by his investigation. (Pannekoek, 1961, p. 325)
- 1 RGO 6/29 97, Airy to Robert Main, 1852 Jan 19. Items from the Airy Papers located among the Royal (...)
7John Herschel, one of the leading astronomers of the nineteenth century, summarised the underlying attitude in a similar manner: “though we are entitled to look for wonders at the hands of scientific artists, we are not to expect miracles.” The new duty of the astronomer was “the detection and compensation of [instrumental and observational] errors, either by annihilating, or by taking account of, and allowing for them” (Herschel, 1849, p. 76-77). This approach to instrumental error reversed the power-balance between the artisan and the astronomer. Possessing the best instrument did not mean the production of the best observations. Instead, it was the mathematical skills of the astronomer that elevated the observations to the required standards and justified their reliability. George Airy was not only a close friend of Herschel but expressed similar thoughts in relation to the work at the Royal Observatory, Greenwich. When his highest ranked assistant, Robert Main, intended to send parts of an instrument to the instrument makers due to being considered defective, Airy sent his assistant the following note: “Generally — never consult an optician about a fault of a telescope till you have thoroughly examined the theory; we understand the theory far better than they do.”1 Theory and mathematics were the tools of astronomical detectives that separated them from the artisans.
8Through this approach, the meridian circles underwent two types of inspections. Upon receiving them, the limits of their perfections were scrutinized and calibrated (Cerda & Valderrama, 2020). This included measuring the accuracy of the graduations on their divided circles and examining the ellipticity of their horizontal axes. Since these inspections were time consuming, they would only be repeated after several years have passed or when major errors were identified. Once a meridian circle became operational, other types of errors were measured (Aubin, 2009). Most crucially, these included the level*, azimuth*, collimation*, and flexure errors of meridian circles (Satterthwaite, 2001b). The errors in the revolutions of the micrometer screws were similarly regularly measured (Brooks, 1991). The distance between the crosshairs inserted into the field of view of the instrument also underwent calibrations. Showing the essential pairing between the astronomical instruments and the clocks, the errors of the clocks were included and accounted for in the final calculations (Schmeidler, 1965). With the introduction of additional instruments into the observing process such as the chronograph*, the errors of such instruments also had to be determined (Lamy & Soulu, 2015). The final calculations also took into account the effect of temperature and air pressure on refraction (Mahan, 1962). It was not enough to carry out these investigations at the time of installing the instruments. The materiality of the instruments was seen to be in a constant state of flux (Baker, 2012). Since instruments were considered to possess the ability to commit a crime at any time, they were placed under constant surveillance and their errors were regularly examined. In summary, the mathematical surveillance of the instruments disassembled them into distinct parts, and then reassembled them on paper using mathematical tools.
- 2 For a full list of the notebooks consult the website of the Project PHaEDRA run by the Wolbach Lib (...)
9The results of these inspections provided values for the instrumental errors. Over the course of a year, these values were compiled into various tables. Such tables formed an essential part of the introductions to meridian observations published by observatories. By the second half of the nineteenth century, these introductions took up almost as many pages in the publications as the results of observations. For example, the publication of the Madras Observatory included tables that showed the corrections for the inclination, runs of the micrometer screw, clock rate, and index errors (Pogson, 1887). The digitised collection of notebooks used in connection with the transit circle of the Harvard College Observatory bear testament of the long calculations that were involved in the process.2 The U.S. Naval Observatory published its “instrumental constants” as a separate appendix for its observations made in 1872 (Eastman, 1873). Therefore, communicating the imperfections of the instruments, and the way in which such imperfections were “rectified” or made “constant,” were essential parts of astronomical detective reports.
10From these, we can infer why Newcomb considered the approach as the reversion of English criminal law. The criminality of the instruments emerged from their constant deviations from their previous states. Through this lens, the instruments did not appear as rigid mechanical objects, but rather, as constantly morphing bodies. They refused to follow the order ascribed to them by the astronomers and instrument makers. They also refused to err in a regular manner. Therefore, the crimes of the instruments were their inability to remain the same and to act in a regular way. Paradoxically, the instruments can also be seen as the ideal criminals from a detective’s perspective. The best instruments were those that were erroneous in a constant and regular manner. Therefore, being a criminal instrument did not matter if the instrument committed its crime on a measurable, predictable, and regular basis. In addition, despite the constant deviations of transit circles, their relatively fixed position meant that they were easy to be placed under constant surveillance. Finally, the transit circles did not commit their crimes alone. The inclusion of errors of other instruments (such as barometers, clocks, chronographs etc.) depicted them as accomplices to the crimes. These several types of criminal activities by the assemblage of instruments had to be collected, analysed, and evaluated. In this way, the published observations became reports on the detected errors that showcased to other astronomers the investigations of astronomical crimes.
11The Airy Transit Circle at the Royal Observatory, Greenwich was an archetype for this type of mathematical management of an instrument. The instrument was installed in a room that previously housed two mural circles. Their piers were reused to ensure the stability of the new transit circle. Artificial stones and special bricks were prepared to ensure that the pivots of the instrument rested on solid foundations. The western pier underwent further modifications as eight pairs of holes were drilled through it to enable viewing (and illuminating) the divided circle on the other side of the pier. A lifting machinery rested on top of both piers that allowed for raising the telescope tube for inspection of the pivots. On the northern and southern ends of the room rested two collimating telescopes for measuring the transit circle’s collimation error. When the telescope tube of the transit circle was lifted, it also enabled the adjustment of the two collimating telescopes to each other. A hole was cut into the western wall of the room to enable a third collimating telescope to be placed in the room for the examinations of the pivot errors of the instrument. In brief, the Airy Transit Circle was not only an instrument designed for observations, but it was also designed to be observed.
12Such an instrument fit within Airy’s transformation of the Observatory during the middle of the nineteenth century. Robert W. Smith (1991), Allan Chapman (1985), and Simon Schaffer (1988) argued that Airy implemented into the management of the Observatory a factory mentality. Following Newcomb’s characterisation of the Observatory, Smith further argued that the implementation of increased division of labour aided the large-scale production of astronomical data. This was achieved using “skeleton forms” (standard forms that only had to be filled out with the relevant values), and the deskilling of the work. It also included the establishment of a rigid hegemony of staff, and the re-instrumentation of the Observatory with a new set of instruments that were manufactured with large-scale astronomical data production in mind. Finally, there was also the “speedy” and regular publication of the observations. The Airy Transit Circle embodied such factory production methods as it allowed for the increased number of observations, produced separate results for instrumental errors to be inserted into skeleton forms, and was designed to be placed under constant surveillance.
13The Airy Transit Circle’s most striking difference among other similar instruments was its size. Transit circles made by instrument makers like Johann Georg Repsold and Georg Friedrich Reichenbach, and even those usually made by Troughton & Simms were made in relatively small size. The small size allowed for making the instrument reversible, which was another way in which its level error could be identified. In contrast to this approach, Airy (who designed the instrument himself) decided to increase the instrument’s size. This was for several reasons. The larger size was assumed to be able to accommodate an object glass that also allowed for transit observations of fainter celestial objects. The development of a new chilled-iron technique for the production of telescope tubes made the larger size a possibility. This method also reduced the weight of the instrument, which otherwise would have led to major problems in relation to the flexure of the tube. Finally, while the larger size made the manipulation of the instrument more demanding, it also enabled the easier measurement of its instrumental errors.
- 3 RGO 6/727 504, John Green to George Airy, [undated, c. 1854]; RGO 6/727 508, George Airy to John G (...)
- 4 Relevant correspondence relating to the modification of the central cube can be found in RGO 6/743 (...)
14The measurement of the instrumental errors was regularly undertaken on Mondays.3 This was partly necessary as the instrument was non-reversible due its large size. As a result, to align the sight* of the two collimator telescopes*, the telescope tube had to be temporarily lifted with the machinery placed on top of the piers. Due to this practice, the instrument required the re-examination of its errors on a regular basis. The practical issues that this lifting raised became apparent quite soon after the instrument was installed. When similar instruments based on Airy’s design were constructed later, they were made with several holes cut through the central cube of the telescope tube’s body. This created a line of sight between the collimators without having to raise the telescope tube. Since the new design proved useful for other large instruments, the Airy Transit Circle also underwent the same modifications. The instrument makers visited the Observatory and they cut several holes through the central cube of the instrument.4 The intervention was a success and future examinations of collimation errors were made using the holes.
- 5 RGO 6/730 388, George Airy to John Green, 12 April 1856; RGO 6/29 47, Robert Main to George Airy, (...)
- 6 RGO 6/726 452, George Airy to John Green, 24 October 1853.
- 7 It is important to note here that to a certain extent, this clear-cut division of labour was uniqu (...)
15The regular maintenance on Mondays continued as it formed an essential role in re-measuring the errors of the instrument. While the measurements were carried out by the Observatory assistants, the physical work of raising and adjusting the telescope was done with the help of the Observatory’s carpenter, John Green. Over the years, Green built up an expert knowledge about the material manipulations of the instrument. When a model of the Airy Transit Circle was installed at the Exposition Universelle of 1855 in Paris, he was even sent to France to help with its installation (Belteki, 2020). Based on the survival archival records, even though assistants also took part in a few experimentation with the adjustments of the instruments (such as its galvanic system and the illumination for the collimators), this was always done in the presence of Green.5 In addition, prior to the installation of a copy of the Airy Transit Circle at the Royal Observatory, Cape of Good Hope, the assistant of that observatory visited Greenwich and received instructions about the maintenance of the instrument from John Green.6 What emerges from this is a division of labour between the carpenter and the assistants that reflected two distinct types of maintenance: material and mathematical.7
- 8 The description of the instrument was published as an appendix to the Greenwich Observations in 18 (...)
16One of the most important instrumental errors of the Airy Transit Circle was the error of the divisions of the graduated circle. The graduated (or divided) circle showed the observer the declination of the celestial body observed. Errors of the graduated circle arose for several reasons. For instance, the material used for creating the circle changed its shape over time due to changes in the temperature or due to its faulty construction. In addition, the level error of the instrument caused the divisions on the circle to appear at different positions. There were additional more practical factors, such as a gradual tarnishing of the division due to cleaning and constant wear. Thereby, re-measuring the errors of these divisions was crucial for accurate observations. When the Airy Transit Circle was first installed, the errors of the divisions underwent in-depth examination, with each degree being examined. The resulting table of errors was published as part of the description of the instrument.8 In subsequent years, the errors continued to be remeasured regularly, but only with the examination of every five degrees. A complete redetermination of the errors of division then began in 1856 and was finished in 1857 by one of the assistants, Edwin Dunkin. A similar examination took place in 1868. The errors so found played a key role in the reductions of the observations. When determining the north polar distances stars, the errors of the measured angles were considered during the calculations. Thereby, the errors of the instrument were not repaired by altering its materiality, but rather, by constantly re-measuring its errors and its deviations from its ideal state. Yet, although it was a criminal act by an instrument to deviate from its ideal state, if such deviations were regular, then the instrument was placed under constant surveillance. By contrast, if the instrument behaved erratically, then the instrument faced corporal punishment. For instance, after the installation of the Transit Circle, Airy and the instrument makers realised that cutting holes through the central cube of the instrument would allow for an easier measurement of the instrument’s errors. As a result, operations were undertaken on site by the instrument makers to perforate the instrument. Similarly, the graduated circle of the instrument was re-graduated on site by the instrument makers in the early 20th century due to the tarnishing of its divisions over the decades of cleaning. The auxiliary instruments associated with the Transit Circle underwent similar modifications. For example, after almost ten years of use, the piers upon which the collimators were fixed were covered by tin screens. This modification was made to guard the collimators (and the piers) from the effects of changing temperatures.
17Examining the errors of the division circle provided useful materials for identifying another systematic error in 1875: the errors of the revolutions of the micrometer screws. The Chief Assistant of the Observatory at the time, William Christie, outlined in a paper how a change in the position of the division in the field of view of the micrometer-microscopes was accompanied with a sensible numerical error (Christie, 1876). This prompted Christie to consider the effects of the wear on the micrometer screws used. He revisited the errors of the divisions measured by Dunkin in the 1850s and the 1860s to see whether the effect of the wear could be delineated that early on. In addition, Christie noticed that the daily observations of the Nadir* prior to 1868 used to be made without specifying at what revolution the micrometer screws should be. This practice was revised in 1868 with instructions to make Nadir observations while keeping the screws at the position of 0 revolution. The examination of these two elements resulted in two fascinating conclusions. First, Christie demonstrated how the results of the 1868 determinations yielded a similar error curve, thereby showing the effect of the wear on the micrometer screws already being present. Second, the changes implemented into the Nadir observations made the threads of the screw between 0 and 1 revolutions be more worn than in any other parts of the screw. As Christie noted, this was due to that part of the screw being used around 4000 times between 1868 and 1876. With such conclusions, it was demonstrated that the wear on the micrometer screws resulted in a systematic error that was not only sensible, but also measurable in a way that allowed for the correction of the observations during calculations. Thereby, Christie was able to unveil a crime of the instrument that had gone undetected since its installation and offered a solution on how to place the instrument under additional surveillance.
18During the 1880s, one of the astronomical assistants at Greenwich, Herbert Hall Turner, wrote several articles about the various instrumental errors of the transit circle. Writing about the collimation error, Turner noted the changes made to the way of measuring this error in 1868 by cutting perforations to the central cube of the telescope tube (Turner, 1886). In subsequent measurements of collimation errors, a discrepancy was discovered between the readings when the instrument was in a raised position or when it remained lowered (and readings were taken through its perforated cube). Although Airy initially thought that the origin of the error was due to poor observations, after several experiments the error was acknowledged as originating from the collimators. Subsequently, from 1874 onwards a numerical correction was always applied when calculating errors of collimation, and the error was placed under weekly surveillance. Since the origin of the error was not found, there was speculation whether the discrepancy was caused by the telescope tube changing the temperature of the room when it was in a raised position (thereby causing changes in refraction) or whether the error originated within the collimators themselves. To test the ideas, a wooden model of the central cube of the transit circle was made and it was placed under the raised telescope during the experiment. By comparing the measurements made with the collimators through the wooden model and through the original cube, the source of the error could be identified. It was found that the issue arose not from the changes in the temperature, but from the position of the collimators slightly changing every time the transit circle was raised.
19Besides monitoring the errors of the instrument, the environment that surrounded it was also placed under surveillance. For instance, transit circles were dependent on the stability of the foundations of their piers. In addition, the ground could cause other troubles by transmitting the vibrations generated by railways or factory machinery — both of which were seen as threats to the work of the Royal Observatory, Greenwich (Macdonald, 2020). Another crucial element was the changes in the temperature and air pressure. William Ellis produced a paper describing the variations of the azimuth and level errors of the Transit Circle between 1851 and 1858 (Ellis, 1861). It noted that the variations followed closely the changes in the external temperature. Turner extended the observations to 1884 to determine how changes in temperature affected the instrument (Turner, 1887). Similarly, to other instrumental errors, the aim was to identify a new constant of error that could be applied mathematically during the reduction of the observations to counteract the instrumental error. Turner’s conclusions argued that the level error was caused by the quicker warming of the eastern pier than the western pier, which subsequently resulted in the eastern parts of the transit circle being affected by temperature sooner than its western parts. Meanwhile, the azimuthal error was argued to be affected by changes to the temperature at some depth below the soil. Turner continued to be concerned about the effects of temperature and in 1893 published a paper that discussed the distribution of the temperature in and around the transit circle room. Although he was unable to establish a constant for accounting for the error during calculations, he was able to demonstrate that the distribution of temperature in the transit-circle room had a sensible influence on zenith*-distance observations (Turner, 1893).
20Turner’s preoccupation with the effect of the changes of the temperature on the transit circle demonstrates an extreme version of the German school of astronomy. The surveillance of the instrument goes beyond its material assemblage. Even the environment surrounding it becomes incorporated as a component of the instrumental assemblage. The heat and the cold radiating through the observing room becomes an accomplice of the instrument. Yet, the aim of the astronomer was not to change the temperature or to stop the circle dance of seasons. Instead, astronomers applied their ardent surveillance of instrumental behaviour to the changes of the environment surrounding it. At the same time, such surveillance conceptually merged the instrument with the environment. In a paradoxical manner, by displacing the instrument into an abstract numerical conceptualisation and reducing the environment into a mathematical form, the instrument was re-placed into an ecological assemblage from which it was originally conceptually detached.
- 9 RGO 6/236 716-719, [Notes on Albert Marth’s paper by Robert Main], [undated, c. November 1859].
21The significance of the mathematical maintenance of the Airy Transit Circle was highlighted by an article published in 1860 in the Astronomische Nachrichten, the leading astronomical journal at the time (Marth, 1860). The article attacked the way in which the errors of the instrument were determined and thereby suggested that the results of the observations were unreliable. It raised five main criticisms relating to the mathematical maintenance of the instrument: (1) Bessel’s refraction tables were deemed unsuitable for the environmental conditions at Greenwich, (2) the errors of the thermometers were not explained well in detail in the published results, (3) the flexure of the telescope tube was determined using an inaccurate method, (4) the errors of the micrometer screws were not taken into account, and (5) the large size of the instrument was considered impractical for the determination of instrumental errors. These criticisms were raised by Albert Marth, who was the director of the Durham Observatory at the time. The article was originally written in 1858 with the aim of being published in the Memoirs of the Royal Astronomical Society. Since the topic of the paper related to the Royal Observatory, Greenwich, Airy was sent a copy to review it. He asked his First Assistant, Robert Main, to examine the paper, who alerted Airy to the scathing criticism that it included.9 However, Main also noted that all the errors mentioned had been remedied since the installation of the instrument.
- 10 RGO 6/236 722, Robert Main to Warren De La Rue, 19 November 1859.
- 11 RGO 6/236 726-727, George Airy to Warren De La Rue, 21 November 1859.
- 12 RGO 6/236 734, Warren De La Rue to George Airy, 10 December 1859.
- 13 RGO 6/13 272-305, [Comments on Albert Marth’s paper by George Airy submitted to the Board of Visit (...)
- 14 RGO 6/236 310, George Airy to William Henry Smyth, 30 October 1860.
22Airy was alarmed by the paper and began a personal campaign within the Royal Astronomical Society to halt the publication of the paper. He even threatened his own resignation from the Council of the Royal Astronomical Society.10 He believed that publishing the paper would have legitimised the criticisms, despite being outdated. In addition, he thought that the paper was an attempt by Richard Carrington to discredit the work done at Greenwich.11 Ultimately, Airy’s wishes were met and the publication of the article was halted. Furthermore, several members of the Society revoked financial support to publish it as a stand-alone pamphlet.12 Such an action prompted Marth to find a different journal, and the Astronomische Nachrichten was willing to publish it. The impact of the paper remains unknown, but it prompted Airy to write a long letter to the Board of Visitors who supervised Airy’s directorship at the Observatory.13 Building upon Main’s initial summary of the paper, the letter responded to each point of criticism raised by Marth, and how they had been countered soon after the installation of the instrument. Airy’s concluding thoughts relating to the incident appear in letters exchanged with his close friend, William Henry Smyth. They both agreed that Marth was unaware of his work being used for a larger attack on Greenwich and its reputation.14
- 15 RGO 6/236 309, William Henry Smyth to George Airy, 29 October 1860.
23The ‘Marthiad’ (as it was labelled by William Henry Smyth) demonstrated that the mathematical maintenance of the Transit Circle was an essential component of its operations.15 Criticising how the instrumental errors were measured and accounted for during the calculations carried significant weight, and even prompted the director of the Observatory to write an explanatory letter to his supervisors. The content of the criticisms highlighted that the various auxiliary instruments used with the transit circle were similarly essential to its operations. Thereby, maintaining the instrument meant not only maintaining its core parts, but also the assemblage of instruments within which it was placed. The errors of the instrument were the errors of its assemblage. Marth put on trial the Transit Circle for crimes that it committed in the past. However, he did not consider that within the panopticon of Greenwich, its behaviour had already been disciplined by the people surveilling it on a daily basis. Mathematics at the Observatory was used to place the instrument under this constant surveillance. This surveillance encompassed the different auxiliary parts of the assemblage too. It became the key tool that disciplined the parts of the assemblage to operate in harmony with each other.
24In the panopticon of the Observatory, instruments and observers were put under strict and regular surveillance. This approach embodied what Simon Newcomb labelled as the German school of astronomy, where the only way to get close to deriving perfect results from observations was by accounting for the errors of observations. The Airy Transit Circle was designed with the aim of being placed in such a system of surveillance. Its various parts invited the astronomical assistants to examine them and gave information about the changes to its various parts. This way, the Airy Transit Circle became the ideal criminal as it laid bare to the astronomical detectives the crimes that it committed and allowed the astronomical judges to devise punishments.
25This article demonstrated how mathematics was used by astronomers as a tool to disassemble and reassemble instruments. Through the works of the Observatory staff working with the Airy Transit Circle we saw how every part of the instrument (even the micrometer screws) were placed under surveillance. This surveillance did not only encompass the immediate materiality of the instrument, but the environment surrounding it. Such an approach reframes instruments as material-ecological assemblages always situated within the environment, rather than as instruments that are abstracted from nature. The Marthiad episode highlighted how significant this mathematical maintenance of the instruments was. Airy saw any criticism of the mathematical practices employed in connection with the Airy Transit Circle as an attack on the reliability, reputation and status of the Royal Observatory, Greenwich. Airy’s extreme reaction to halt the publication of Marth’s paper in Britain highlighted the fundamental role that mathematics as a tool played within the operations observatories during the nineteenth century.
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