Otto von Guericke’s Cometary Theory in Stanisław Lubieniecki’s Correspondence

Introduction

Otto von Guericke’s (1602–1686) Experimenta nova (ut vocantur) Magdeburgica de vacuo spatio (Amsterdam, 1672) [The New (so-called) Magdeburg Experiments on Empty Space] was one of the pioneering works on the vacuum, air, and barometric pressure. ¹ It also presented the author’s views on the nature of the universe. Guericke was a proponent of the Copernican heliocentric system, which he found superior to Aristotelian-Ptolemaic and Tychonian models. Furthermore, he rejected the existence of one sphere of fixed stars and argued for the infinite universe.

A relatively short passage in Guericke’s publication is devoted to comets. The author proposed his own theory of the origin of tailed stars. According to this theory, comets are parts of the air carried by storms into the vacuum and illuminated by solar rays. Guericke’s theory was quite innovative in his time, given the fact that it required two premises which were relatively new and still controversial: the existence of the vacuum and the heliocentric model of the universe.

Guericke’s idea is presented in the appendix to Book Five of the Experimenta nova, titled “The globe of land and sea and its companion, the Moon” (De terraqueo globo et eius socia quae vocatur Luna). However, it was not the author’s original intention to discuss cometary phenomena in his book, as is apparent from the opening passage:

Although it was not my intent to write anything about comets, still an opportunity was presented when one or another comet of significant size appeared about the end of 1664 and the beginning of 1665, at which time this treatise had already been finished for a year. It so happened that my opinion as to their nature was sought by several men, among whom was the most noble gentleman, Stanisław Lubieniecki, a Polish knight. In view of our subsequent correspondence, he included and published the letters he had sent to me and my answers in return in the order in which they were written in his Theatrum cometicum, pages 453 to 465, which was printed in Amsterdam in 1668. ²

As Guericke confessed, the main reason why he had written about comets was inquiries from Stanisław Lubieniecki (1623–1675) ³ who was a Polish nobleman and a religious refugee. He was an adherent of the Polish Brethren – followers of the Unitarian faith who opposed the dogma of the Holy Trinity. When his fellow believers were expelled from Poland and Lithuania in 1658, Lubieniecki settled in Hamburg. In exile, he continued his earlier confessional, polemical, and historiographical activities, but he earned his living as an intelligencer of political information for a few royal courts and some people of importance. Apart from his religious and spying activities, he wrote the Theatrum cometicum, a book about comets. Its first and third volumes – Theatri cometici pars prior (Amsterdam, 1668) and Theatri cometici exitus (Amsterdam, 1668) – contain his correspondence pertaining to astronomy. Inspired by the comets of late 1664 and early 1665 (C/1664 W1 and C/1665 F1), Lubieniecki established contacts with astronomers and other scholars in order to learn more about the recent phenomena. At the same time, he collected various data regarding historical appearances of comets. He published them in a catalogue of comets in the second volume of Theatrum cometicum (Theatri cometici pars posterior, Amsterdam, 1666). Lubieniecki’s interests in astronomy were rather ephemeral and the Theatrum cometicum is their only trace. Yet, it is an unexplored source of lesser known, and often less important, scientific discussions in the early modern period. ⁴

Lubieniecki learned about Guericke’s cometary theory from his son and namesake, Otto von Guericke Junior (1628–1704), who was an emissary of the Prince-Elector of Brandenburg in Hamburg. Guericke’s son also presented to Lubieniecki his father’s invention – a device for investigating changes in the air. Fascinated by Guericke’s cometary theory, Lubieniecki decided to contact the author.

The aim of my article is twofold. First, it presents Guericke’s cometary theory derived from the Experimenta nova. Guericke’s reprint of his correspondence with Lubieniecki is the most comprehensive description of the cometary theory he ever made. It also allows us to catch a glimpse of some aspects of its development with regard to what Lubieniecki found interesting there, and how Guericke reacted to his questions and remarks. To this end, I present this correspondence letter by letter, focusing on the information vital for describing and understanding Guericke’s cometary theory.

The second aim of my text is to present what was written about Guericke’s cometary theory in Lubieniecki’s Theatrum cometicum. Apart from discussing the theory with the author, he wrote about it to his correspondents, and their answers are the only place from which we may learn how contemporary scholars perceived Guericke’s theory. Theatrum cometicum has been almost entirely neglected as a source of information about Guericke’s cometary theory, and the present study aims to shed some new light on this subject.

Status quaestionis

So far, Guericke’s cometary theory has been considered solely in the context of his studies, and the attempts to describe his views on comets have been rather scarce. A full description of the theory, based on the entire corpus of Guericke’s and Lubieniecki’s letters, has not been presented yet. Moreover, even when Lubieniecki is mentioned as Guericke’s correspondent, references to his Theatrum cometicum are even rarer.

In a text written to commemorate the 300th anniversary of Guericke’s birth, Ludwig Blath has briefly mentioned Lubieniecki’s correspondence with Guericke and his son, and has described Guericke’s theory of the origins of comets. ⁵ He has also pointed out that the author of the Experimenta nova was not overly interested in comets and he never meant to study them. The paper has not investigated the foundations of Guericke’s theory.

Wilhelm Ahrens has described Lubieniecki’s correspondence with Guericke and his son in an article about Guericke’s scholarly contacts. ⁶ However, except for summarizing Guericke’s claims on his ability to predict comets, Ahrens has not described the cometary theory itself.

Julius Laumann has presented the most important elements and experimental foundations of Guericke’s theory on the basis of the author’s letters to Lubieniecki. ⁷ Laumann published a German translation of substantial passages from Guericke’s letters: concerning the universe, the Earth, and the air (in a letter sent on 29 May 1665), experimental bases of the cometary theory and its role in predicting cometary phenomena (1 August 1665), his opinions about the space and vacuum, and further remarks about predicting comets (12 April 1666); the letters are discussed below. The article lacks, however, a sufficient commentary, and the letters are prefaced only by some general remarks about Lubieniecki and his correspondence with Guericke and his son. Even though the selection of correspondence did justice to the main foundations of Guericke’s theory, the lack of Lubieniecki’s letters made it devoid of context. For example, Guericke’s discussion of space and vacuum is an answer to Lubieniecki’s account of a discussion in which his friend (identified by me as Joachim Stegmann) took part, which was sent by Lubieniecki to Guericke on 15 August 1665. Moreover, in Laumann’s article, there are some alterations in the letters which could have been made in order to facilitate the reader’s understanding of Guericke’s ideas, but there are no indications that the text was changed. For example, the information about the number of the layers of the air is placed in the letter sent on 29 May 1665, whereas in Guericke’s book, it was printed in the letter dated 1 August 1665. ⁸ Finally, the publication is based on Guericke’s Experimenta nova only. Therefore, it lacks any information about the discrepancies between the letters in Guericke’s book and their original form in Lubieniecki’s Theatrum cometicum. This could lead to a conclusion that Guericke was willing to accept supernatural influences on strong winds, whereas, as discussed below, his original opinion was more nuanced and it evolved with time.

Fritz Krafft’s commentary to the German translation of Book Five of Experimenta nova has presented Guericke’s correspondence with Lubieniecki as a part of Guericke’s work. ⁹ It has not focused on Guericke’s cometary theory but related his statements concerning the generation of comets to his other opinions and experiments. As far as Lubieniecki’s book is concerned, the commentary is rather sparse. Apart from the correspondence between Lubieniecki and Guericke, the German edition of the Experimenta nova also contains a translation of the excerpts from the correspondence between Lubieniecki and Guericke’s son from the Theatrum cometicum. ¹⁰

Fritz Krafft also has mentioned Guericke’s cometary theory and his correspondence with Lubieniecki in the biography of the author of the Experimenta nova, but he has rather focused on Guericke’s claims that he has been able to predict comets, and on Guericke’s invention for investigating changes in the weight of the air. ¹¹ Krafft has listed some people to whom Lubieniecki wrote about Guericke’s theory, but without describing the letters or reactions to the theory.

In his discussion of early modern cometary theories, Andrea Gualandi has mentioned Guericke’s theory. ¹² In his description of Lubieniecki’s Theatrum cometicum, Gualandi has observed that Guericke, who based his considerations on comets on the existence of the vacuum and the acceptance of the heliocentric model of the universe, suggested that comets can originate from the particles of the air lifted by strong winds. Moreover, Gualandi attempts to present Guericke’s theory against the background of the Theatrum cometicum and he notes that some of Lubieniecki’s correspondents made some objections to Guericke’s theory. He quotes Johann Melchior Røtlin and Giovanni Battista Riccioli (see below).

The Guericke-Lubieniecki correspondence

Because the Experimenta nova, originally written in Latin, has been published in modern languages – in English ¹³ and in German with commentary ¹⁴ – there is no need for a detailed discussion of each of the letters here. I will rather summarize their contents, focusing on their importance for Guericke’s cometary theory.

The first letter of the correspondence was sent by Lubieniecki on 14 March 1665. ¹⁵ He started by mentioning his friendship with Guericke’s son. Lubieniecki wrote that he learned from him about his father’s cometary theory and would like to know more about it. Lubieniecki found some ideas similar to Guericke’s theory in the works of earlier scholars – Epigenes of Byzantium, Petrus Apianus, Girolamo Cardano, and Julius Cesar Scaliger – and asked Guericke about them. Moreover, he was interested in the idea that storms may be caused by evil spirits or even by supernatural forces which act by the orders of God. He implied that the comets may have supernatural origins. He referred to a passage from the biblical Book of Job in which the death of Job’s children in a collapsing house was caused by a strong wind. ¹⁶

Guericke’s answer, dated 29 May 1665, was rather brief. ¹⁷ He informed Lubieniecki that he would discuss his cometary theory in the book he planned to publish. He did not want to write more about his theory of tailed stars, because the exhaustive description would be too long for a letter. He only summarized his opinions about the infinite space with many suns, about the heliocentric model of the solar system, and about the nature of the air around the Earth. He dismissed the opinions of earlier scholars sent by Lubieniecki by remarking that he did not have the books of the authors his correspondent had mentioned. As for the idea of the supernatural influences, Guericke seemed rather cautious and emphasized that one should be very precise while speaking about such forces and their influence on nature.

Another letter by Lubieniecki, dated 13 June 1665, was sent before he received Guericke’s answer. ¹⁸ Lubieniecki wanted to learn more about his correspondent’s views on the movement of the Earth. He listed well-known authorities who supported, or were assumed to support, that idea: Pythagoras, Plato, Nicolaus of Cusa, and Nicolaus Copernicus. This is, however, the only passage in which Lubieniecki showed interest in linking Guericke’s cometary theory to the heliocentric model of the universe.

However reluctant to discuss cometary phenomena, Guericke decided to answer Lubieniecki’s request and on 1 August 1665, he sent him a more detailed description of the cometary theory, founded on the considerations and experiments presented in his book, where, as he repeated, he meant to elaborate on his worldview and discoveries. ¹⁹ He presented five main points from which he drew his conclusions:

Having established these premises, Guericke proceeded to his cometary theory. First, he emphasized that storms can move into any direction, therefore they can move upwards as well. And because comets, when observed with a telescope, look similar to dense clouds, he supposed that they are parts of the air, carried upwards into the layers of thin air or into the vacuum, where they are illuminated by solar rays. The higher the comet is, the smaller its tail is, because it stretches due to the dispersion of sunlight in the air. However, Guericke remained cautious about the results of astronomical studies. He agreed that comets are above the Moon and can be bigger than the Earth, but he claimed there was no – and could not be any – agreement about comets’ exact distance from the Earth, their place among the stars, and their real size. Guericke ended his letter with some remarks about the movement of comets. According to him, comets in the vacuum remain stationary, while the Earth in its annual movement around the Sun can sometimes approach them. The only motion comets can have is caused by the Sun’s attraction. Guericke explained it with the results of his experiments which showed that fire consumes air.

Guericke’s description was quite exhaustive, but it seemingly did not satisfy Lubieniecki. On 15 August 1665, he sent to Guericke a long list of ideas and concepts which he found similar to Guericke’s theory. ²¹ (The most important of them are discussed below.) Probably incited by the fact that Guericke admitted he had not had the texts by scholars Lubieniecki mentioned, he decided to pursue this topic. In the letter, Lubieniecki referred to a number of philosophers, scholars, and theologians in a lengthy and convoluted passage. The structure of the letter seems to indicate that Lubieniecki worked in a hurry and did not have the time to organize his thoughts and words. He started with a discussion of the views which considered comets to be somehow related to air. He described the views attributed to Epigenes of Byzantium. He also briefly referred to other scholars mentioned in his earlier letter: Petrus Apianus, Girolamo Cardano, and Julius Cesar Scaliger. Then Lubieniecki proceeded to the issue of supernatural influence on tailed stars – this time, as if he wanted to mitigate the bad impression created by his earlier suggestions about demons causing winds, he focused on the deeds of angels who fulfil the will of God and on divine influence on comets. Among others, he mentioned Christoph Rothmann, ²² Libert Froidmont, ²³ and John of Damascus. ²⁴ Lubieniecki remarked, however, that the matter in question should be approached cautiously. Finally, he finished the letter by listing – without many details about their views – philosophers, scholars, and thinkers who believed comets to be temporary bodies, of either celestial or terrestrial nature, which are illuminated or ignited. Among names he mentioned there, there were Tycho, Kepler, Galileo, and Descartes, and some lesser known people as well.

Lubieniecki quoted his sources mostly derived from Almagestum novum (Bologna, 1651) by Giovanni Battista Riccioli. This is especially visible in the last part of Lubieniecki’s letter, where he almost literally copied the names of scholars from the discussion of various cometary opinions in the Almagestum novum. Some other pieces of information were given after Singularium pars secunda (Frankfurt, 1599) by Andreas Libavius. ²⁵ Among the many authors and opinions Lubieniecki mentioned, I will focus on those which he had already quoted in his first letter to Guericke and discussed in detail in this one. He seemed to consider them the most important, and he referred to them when he described Guericke’s theory to his other correspondents. ²⁶

First, Lubieniecki mentioned Epigenes of Byzantium, a very little-known ancient thinker, who claimed that comets were caused by whirlwinds and set ablaze by violent movements of the air. Lubieniecki learned about Epigenes from Libavius’s Singularia ²⁷ who, in turn, based his description of Epigenes’s views on Senaca’s Natural questions. ²⁸ In Libavius’s opinion, there was a similarity between Epigenes’s cometary theory and that of the Peripatetic school – namely, that comets are terrestrial exhalations which are carried upwards and are set on fire in the upper parts of the sublunary region. Such conjunction of opinions, however, seems to be Libavius’s invention, as neither Seneca nor other sources of Epigenes’s views mention this connection. Lubieniecki did not hint that Libavius described Epigenes’s views after Seneca’s treatise, even though in the subsequent part of the letter he referred to Seneca’s description of Epigenes’s view. ²⁹

Another scholar, also featured in Libavius’s book, ³⁰ was Petrus Apianus who was said to consider comets as particles of the air, illuminated by the Sun. Tracing the origins of this opinion is difficult. Fritz Krafft presumed that the source could be Apianus’s Astronomicum caesareum ([Ingolstadt], 1540). In this work, Apianus described comets and concluded that the direction of their tails is related to the position of the Sun. ³¹ Krafft also remarked that in his letter to a Danish courtier, Johannes Melchior Røtlin, Lubieniecki gave the Systema physicum (Hanau, 1623) by Batholomaeus Keckermann as the source of the information. ³² Keckermann wrote there that Apianus thought comets to be terrestrial exhalations whose glare and tails are caused by the Sun. ³³ However, he did not quote any works by Apianus.

The last of the chief similar opinions found by Lubieniecki is quite puzzling. He referred to the statements of Girolamo Cardano and Julius Cesar Scaliger as if they were unanimous in their views on comets. In fact, they could not be further apart – Cardano believed that comets are celestial phenomena, ³⁴ while Scaliger defended the Aristotelian opinion about comets as terrestrial exhalations. ³⁵ Lubieniecki referred to a chapter in Scaliger’s Exotericarum exercitationum liber quintus decimus (Paris, 1557) – the Exercitatio 79 – in which the author opposed Cardano’s opinions on comets. They both, however, agreed that comets are only illuminated, and not ignited, by the Sun. In his letter to Guericke, Lubieniecki did not pay any attention to the details of the controversy between Cardano and Scaliger, but he simply pointed out a mutual aspect of their views which seemed to correspond with Guericke’s theory. ³⁶

Having sent a robust and detailed letter, Lubieniecki was hoping that Guericke would elaborate more on his views on comets. Guericke, however, failed to meet these expectations and Lubieniecki’s letter remained unanswered for a long time. Having received no response, Lubieniecki sent another letter to Guericke on 27 March 1666. He repeated his pleas formulated in the preceding letter. ³⁷

This time, Guericke did not make Lubieniecki wait too long. He answered on 12 April 1666. ³⁸ In the letter, he briefly replied to list of opinions conveyed by Lubieniecki and repeated the main points of his cometary theory. He briefly summarized his view on the generation of comets:

I answer, however, that it is not my opinion that the substance of comets originates from exhalations of the earth and, through the agency of the Sun’s rays, rises. Rather I believe that their matter has its source in a kind of whirlwind generated in the bowels of the earth, which sailors call Orcan, and in bursting forth from the caverns of the earth and mountains, it draws to itself a particle of air (as all whirlwinds tend to do). Enveloped by this whirlwind, the air is carried farther and farther upwards, and does not, as one might expect, descend to the Earth, until it reaches that region where air is greatly rarefied and there is no wind. Furthermore, because of its innate whirling nature, this body wanders here and there like a ball of fire, being illuminated by the Sun (when it comes out from the shadow of the Earth) in the manner of the clouds, and is ultimately consumed by the sun. In my letter to you of July 22 of the past year I explained this in detail in essentially identical terms.

As to whether or not whirlwinds of this kind are excited or produced in the bowels of the Earth by spirits, it is difficult to say, nor would I readily dare to give an answer. Rather I should say that there are some living essences, or even animated spirits, which are generated there for the production of storms of this kind and then die out again. ³⁹

As Guericke pointed out, many scholars Lubieniecki referred to described comets according to the Aristotelian worldview, that is, as terrestrial exhalations, while, in his opinion, they were particles of the air. Therefore, Guericke saw no reason to discuss the whole list in detail. His laconic answer could be also caused by the way Lubieniecki presented those views – with a few exceptions, he quoted them after Riccioli without giving any details.

In the last letter of the correspondence, sent on 29 April 1666, Lubieniecki thanked Guericke for his answer. ⁴⁰ He also tried to justify his earlier allusions to demonic influence on weather phenomena by saying that these were views held by some learned men and by the common opinion. Lubieniecki added that he did not have his own view on this matter.

The correspondence in Lubieniecki’s Theatrum cometicum

As Guericke stated in the Experimenta nova, his correspondence with Lubieniecki had been published in Lubieniecki’s Theatrum cometicum. When we compare the letters in these two works, some differences can be found. They occur only in Guericke’s letters and are the results of the progress in Guericke’s studies. The correspondence was probably reprinted after Lubieniecki’s book. ⁴¹

The majority of these alterations can be found in Guericke’s description of his deliberations and experiments. ⁴² Most of them are rather minor. In the Theatrum cometicum, the pressure of the air around the Earth is given as equal to the pressure of water 20 Magdeburg cubits deep – not 19 or 20, as in the Experimenta nova. In the Experimenta nova, the number of layers of the air is given as three, in the Theatrum cometicum it is four. A more significant difference can be found in the estimation of how far the air stretches around the Earth – in the Theatrum cometicum, the numbers are 10 times bigger: ten or twenty thousand German miles, instead of one or two thousand in the Experimenta nova.

An interesting and important change can be found in Guericke’s last letter to Lubieniecki. As has been remarked, Lubieniecki was interested in the possibility of demonic or angelic influences on winds, while Guericke was rather reluctant to discuss this subject. In his last letter, however, he speculated about “living essences” and “animated spirits” which could participate in the generation of winds. In the Theatrum cometicum, this sentence is missing – Guericke concluded that such supernatural influences are too vague to be discussed. ⁴³ The evolution of the passage may suggest a shift in Guericke’s outlook. It may be speculated that Guericke gave this topic some more thought as a result of his correspondence with Lubieniecki. Moreover, in the Experimenta nova, Guericke omitted the initial explanations of his prolonged silence – in the Theatrum cometicum, one can read that the reason was his sickness. ⁴⁴

Lubieniecki’s correspondence with Guericke’s son

In Lubieniecki’s Theatrum cometicum, the letters are organized by names and usually one chapter contains the author’s correspondence with one person. The correspondent’s name and his place of residence are given in the title of the chapter. Therefore, Lubieniecki’s correspondence with Guericke is printed in Communicatio Magdeburgo-Guerichiana – “the correspondence with Guericke in Magdeburg” – which, as stated by Guericke in the Experimenta nova, is printed on pages 453–65 of the book. Nevertheless, apart from the aforementioned changes, the reprint is not complete.

As said before, Lubieniecki in Hamburg was in touch with Otto von Guericke’s son (in the following discussion, I will refer to them as “Guericke Senior” and “Guericke Junior”) and he learned about Guericke Senior’s cometary theory from Guericke Junior. It seems that at the beginning of Lubieniecki’s correspondence with Guericke Senior, it was Guericke Junior who passed the letters. Guericke Senior did not answer Lubieniecki’s first letter. Instead, he wrote a few words meant for him in a letter to his son. This passage was published in the Theatrum cometicum, but was omitted in the Experimenta nova. Therefore, the order of the early letters in the Experimenta nova differs from that in the Theatrum cometicum, as given in Table 1. The subsequent letters are printed in the same order in both books.

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Table 1.

Chronology of the early correspondence between Guericke Senior and Lubieniecki.

Date and sender of the letter	Number (pages) in the Experimenta nova	Number (pages) in the Theatrum cometicum
14 March 1665, Lubieniecki	1. (184–5)	1. (453–4)
26 March 1665, 45 Guericke (to his son)	(omitted)	2. (454–5)
29 May 1665, Guericke	2. (186)	4. (455–6)
3 June 1665, Lubieniecki	3. (187)	3. (455)

In the letter to his son, Guericke Senior wrote that he had nothing to add to his cometary considerations and he reaffirmed them. ⁴⁶ Those considerations were referred to Lubieniecki by Guericke Junior and can be found in his chapter in the Theatrum cometicum, that is, Communicatio Hamburgi-Gerrichiana, “the correspondence with Guericke in Hamburg.” ⁴⁷ Guericke Junior’s description of his father’s cometary theory is worth quoting, as it was this passage which brought Lubieniecki’s attention to the subject. It was also reported by Lubieniecki to his other correspondents, for example, to Johannes Hevelius. ⁴⁸

The most general cause of comets is God, the secondary causes are storms. First of all, it should be known that the Earth and the air compose one body; the air is placed around the Earth with certain weight and certain height. That body of land and water, together with the air, is placed, or occupies a place, in a universal space or a vacuum where all the celestial bodies are – for the Earth is also a celestial body; the Earth in this space completes its route around the Sun in a year’s time. Therefore, whenever extraordinary storms occur, with their force they cause a small part of the air separate from the aerial ring into that space. That small aerial part takes brightness from the Sun (like dawn, clouds, or planets) and does it in such a way that it sticks in this vacuum or space where there are no other created things. So when the Earth makes its circular route around the centre, then that small part – that is a comet – appears. And the change of the place of the Earth and the Sun by its attraction cause the route and the movement of the comet. This is what I briefly wanted to sketch or describe. This is the first draft and if I am not wrong, this is my father’s idea and opinion. ⁴⁹

This passage, even though it lacks references to Guericke Senior’s experiments and speculations about the vacuum and the universe, is exhaustive enough. It discusses the nature, origin, and causes of the movement of comets. Given its coherence, it is not surprising that it allured someone interested in cometary astronomy. Moreover, as we can see, there is no discussion of the supernatural causes of winds – and, in consequence, comets. It may support the assumption that Guericke Senior’s remarks about them in the letter in the Experimenta nova were his later deliberations, possibly inspired by his correspondence with Lubieniecki.

In his endeavours to promote his father’s work, Guericke Junior did not limit himself to sharing with Lubieniecki the foregoing description of the theory. Guericke Junior passed to Lubieniecki the excerpts from his father’s planned publication. Among them, there were tables of contents of Book One (about various systems of the universe and about planets and stars) and Book Two (in which Guericke discusses concepts of place, space, and vacuum). There were also selected chapters from Book Two: Chapter 4, including definition of space, and Chapter 7, which considers the question of created and uncreated beings. They are printed in the Theatrum cometicum together with the title page of the Experimenta nova. Guericke Junior, however, did not explain why he had decided to share with Lubieniecki those particular passages from his father’s book. He wrote only that he had recently received them from his father. ⁵⁰

Moreover, Guericke Junior passed to his addressee further details about his father’s views which focused on the practical application of his cometary theory, namely, on how comets can be predicted within its framework.

Predictions of comets

Lubieniecki learned from Guericke Junior that Guericke Senior claimed to be able to predict comets. Guericke Junior passed him his father’s observation, dated 2 December 1664, ⁵¹ in which Guericke Senior asserted that he had foreseen a comet 8 weeks earlier and had asked the city guards to watch out for it. ⁵² He made a similar remark about the second comet in his message for Lubieniecki, sent via his son on 26 March 1665. He stated that he had known since 12 February 1665 that there would be the second comet, but he had not announced this prediction, being afraid of criticism. ⁵³

Guericke Senior’s predictions were based on his experiments and observations of the air. Moreover, he was sure that he had invented a device which could forecast comets. In both aforementioned claims, Guericke Senior and Junior alleged that the predictions were made with the help of an instrument devised for indicating incoming storms and rains. Guericke Senior called that apparatus “that little man which shows changes in the air” (homullus ille mutationis aeris index), and his son reminded Lubieniecki that he had showed him the instrument. Lubieniecki featured it in his Theatrum cometicum with a caption:

The illustration of the anemoscope, or the statue enclosed into a glass empty of air which shows changes in the air, invented by the greatest Master Otto von Guericke, councillor of Magdeburg, included in the correspondence with the most noble Master Otto von Guericke, counsellor and ambassador of the Elector of Brandenburg. ⁵⁴

Its mechanism was described by Guericke Junior in his letter to Lubieniecki. The little man (labelled A) can ascend or descend (see Figure 1). The line B indicates the middle point of the scale. When the finger of the little man is near the line and the figure descends, the air will turn to humid; when it ascends, the air will turn to dry. The farther the finger is from the line, the more humid or drier the weather will be. If the little man falls rapidly near the letter C, it announces imminent storms. ⁵⁵ Unfortunately, in the Theatrum cometicum, there is no description of the construction of the device. It cannot be found either in Guericke’s Experimenta nova ⁵⁶ or Gaspar Schott’s Technica curiosa (Nurnberg, 1664) – a work which also discusses Guericke’s works and experiments. ⁵⁷ This absence was pointed out in the review of Guericke’s publication in the Philosophical Transactions. ⁵⁸

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Figure 1.

Guericke’s device for foreseeing changes in the air. Stanisław Lubieniecki, Theatri cometici pars prior (Amsterdam, 1668). National Library in Warsaw, SD XVII.4.2660. Public domain, source: polona.pl (accessed 10 January 2019).

Guericke Senior emphasized and repeated that his invention was based on the premise that the weight of the air can change and that this alteration is related to the changes in the weather. He claimed that he could predict storms which were one or two hundred miles away. ⁵⁹ And because the comets, as he supposed, were caused by storms and strong winds, the “little man” turned out useful also for predicting tailed stars. Nevertheless, he admitted that he had not fully understood the nature of this phenomenon and he did not know how to predict the place of an incoming storm. ⁶⁰

Guericke was not the first one to notice changes of the weight of the air and experiments with barometer have already been conducted in the first half of the seventeenth century. ⁶¹ Nevertheless, it was his original idea to connect the weight of the air to cometary phenomena. It was impossible to foresee a comet in the seventeenth century, and this is probably the reason why Lubieniecki was so interested in Guericke’s theory – it claimed to explain the inexplicable. On the basis of serious experiments and considerations, it presented a coherent description of the nature of comets and a tool to predict them.

Contemporaries’ reactions to Guericke’s theory

Apart from Guericke Senior and Guericke Junior, among Lubieniecki’s correspondents there were about 40 other astronomers and scholars. To some of them, Lubieniecki sent the description of Guericke’s cometary theory and asked for their opinions. Therefore, Lubieniecki’s Theatrum cometicum can tell us how the contemporaries reacted to Guericke’s ideas.

To some of his correspondents, Lubieniecki sent the first description of Guericke Senior’s theory which he received from Guericke Junior. This is often confusing for the reader of the Theatrum cometicum, because the description is only mentioned in the letters and was conveyed to the addressee in enclosures which were not printed with the letters. For example, this applies to Lubieniecki’s letters to Johannes Hevelius ⁶² and Ismaël Boulliau ⁶³ – the astronomers were told that they could learn about it from the enclosed materials. Sometimes the existence of such an enclosure has to be inferred from the correspondent’s answer, as in the case of Lubieniecki’s correspondence with the German naturalist Adam Olearius. In Lubieniecki’s letter, there is only a passing remark about various enclosures without any specification, whereas Guericke’s theory is mentioned in Olearius’s answer. ⁶⁴

Sometimes Lubieniecki was paraphrasing Guericke’s theory in the main body of the letter. For example, this is how he explained its main points to Athanasius Kircher:

For he [Guericke], having presupposed two very difficult and fiercely disputed (as you know better than I do) principles about the movement of the Earth and the vacuum, claims that comets originate from storms which carry separated particles of the air upwards. He affirms that the figure enclosed in the glass emptied of air, by going downwards, demonstrates that the air becomes lighter – I saw it many times myself in the house of his son, the ambassador of the most serene Elector of Brandenburg in this city. He thinks that the particle of the air is carried then to a place where it shows a tail, illuminated by solar rays. ⁶⁵

The description is followed by some additional remarks, including the opinions by Epigenes, Apianus, Cardano, and Scaliger. This list was also sent to others, for example, to the Danish courtier and diplomat Johannes Melchior Røtlin. ⁶⁶

Kircher, as many others, did not respond to Lubieniecki’s information about Guericke’s theory. Lubieniecki did not receive any reactions to his reports on the cometary theory from Johann Raue, the librarian of the Elector of Brandenburg, ⁶⁷ the mathematician Andreas Concius, ⁶⁸ and the mathematician and astronomer Samuel Carolus Kechelius van Hollesteyn. ⁶⁹

Whenever Lubieniecki’s correspondents did reply, they either criticized or refuted Guericke’s theory. Only few of them found this idea worth further consideration. One of those who seemed to be willing to accept Guericke’s opinion was the mathematician Heinrich Sivers. He wrote to Lubieniecki that he found the theory to some extent probable but difficult to prove because it was based on many hypotheses. ⁷⁰ Another favourable opinion was expressed by the aforementioned Olearius who stated that Guericke’s theory should not be rejected because it supported the heliocentric system. ⁷¹

As Lubieniecki noted, in order to accept Guericke’s cometary theory, it was necessary to accept its two controversial prerequisites: the heliocentric model of the universe and the existence of the vacuum. Some of his correspondents refuted the theory because they did not accept these premises. For example, Giovanni Battista Riccioli answered that he disagreed with Guericke’s opinion because he considered both the movement of the Earth and the vacuum to be false concepts. ⁷² Mathematician and physician Johannes von Leunenschloss, despite praising Guericke for accepting the heliocentric system, did not agree with the existence of the vacuum and, therefore, rejected his cometary theory. ⁷³ Even though he did not state his own opinion on Guericke’s theory, Erasmus Bartholin pointed out that the arguments against vacuum are also arguments against this idea. ⁷⁴

There was also another kind of arguments against Guericke’s theory – based not on cosmological views but on cometary observations. Mathematician Johann Müller considered Guericke’s definition of the origin of comets intriguing but he stressed that the theory was wrong as far as their movement was concerned. He emphasized that the route of the comet in December 1664 could not be explained only by the annual movement of the Earth. ⁷⁵ Also Boulliau remarked that the comets are not motionless but have their own movement. ⁷⁶

Other correspondents objected to Guericke’s cometary theory on various grounds. Philosopher Abraham de Grau, an adherent to the Cartesian worldview, emphasized that philosophy and mathematics do not admit the possibility of an aerial generation of comets. ⁷⁷ Johann Melchior Røtlin speculated that if Guericke’s theory had been correct, the storm would have captured not a part but the whole air around the Earth. Moreover, he added that according to observations, comets are bigger than the sphere of air. ⁷⁸ This objection was refuted by Guericke’s conclusion that the air can expand.

Also, the idea that a comet can be predicted on the basis of Guericke’s inventions did not convince Lubieniecki’s correspondents. Hevelius wrote that all such cometary predictions are groundless. ⁷⁹ An interesting response was sent to Lubieniecki by an astronomer Friedrich Büthner. Although he agreed that Guericke’s instrument with the “little man” can predict comets, he added that “this kind of comets is not of our type.” ⁸⁰ He explained that since Aristotle’s times, the name of comets was also given to some meteorological phenomena and that this homonymy obstructed studies and investigations.

Very few of his correspondents’ reactions were passed by Lubieniecki to Guericke. The reason was probably that the intensity of their correspondence was relatively low. Lubieniecki sent to Guericke reservations expressed by Leunenschloss and Riccioli. ⁸¹ He also brought to Guericke’s attention the inconsistency of his theory with the observed movement of comets. ⁸² Guericke replied that comets which are still in the upper layers of the cosmological sphere of air can move because of winds and only the comets beyond that sphere are motionless. They can be attracted, however, by the fire of the Sun. ⁸³ Lubieniecki also passed to Guericke the discussion about the vacuum which was recounted by Joachim Stegmann (not mentioning him by name), who was a theologian and activist of the Polish Brethren. ⁸⁴ As Stegmann wrote, a polemist of his claimed that since space has dimensions, it is a body, therefore, it cannot be a vacuum, and there cannot be space without a body. ⁸⁵ Guericke answered that the space is what is able to take objects inside and it has no dimensions. The space is immobile and indivisible and it is as big as the objects inside it. The dimensions are qualities of bodies, not of space. Moreover, his experiments proved that space can exist without a body. He also added that this subject would be discussed in his book. ⁸⁶

It should be observed that Guericke’s theory is present only in Lubieniecki’s early letters. Most of them come from the first half of 1665, and the theory vanishes from his correspondence in the first half of 1666, when Guericke reluctantly answered the letters and finished their correspondence. It can be concluded that lack of interest among his correspondents and Guericke’s aversion to discuss his theory convinced Lubieniecki to stop writing about it.

Lubieniecki’s opinion about Guericke’s theory

As becomes obvious from his letters, Lubieniecki made a lot of effort to promote Guericke’s cometary theory – he was looking for similar opinions in order to situate this idea against a wider background, and he tried to spark his correspondents’ interest, hoping to verify the theory in scholarly discussions. Therefore, it is quite surprising that he did not express his own opinion about Guericke’s theory. In the Theatrum cometicum, Lubieniecki mentioned the theory as probable only once. ⁸⁷ In all other instances, he reported it without disclosing his own views.

There is, however, a very strong suggestion that Lubieniecki disagreed with some aspects of Guericke’s theory. After further studies and considerations, Lubieniecki took a view incompatible with this theory. In the third volume of the Theatrum cometicum, prompted by Frans Kuyper, the publisher of the book, Lubieniecki discussed and clarified his views on the possibility of cometary influence on the Earth. He claimed that no physical influence of this kind was possible. Consequently, he stated that in his opinion, comets were not related to the cosmological sphere of air. ⁸⁸ Despite the fact that this statement was not made in the context of Guericke’s cometary theory, it clearly contradicts the idea that comets are generated from air.

Guericke and contemporary cometary theories

In his correspondence with Lubieniecki, Guericke emphasized that comets were not his main field of research. He seemingly did not relate his cometary theory to contemporary discussions about the nature and origin of tailed stars. Guericke’s cometary theory was a spinoff of his experiments with the vacuum and the contemplations on the nature of the universe. Therefore, from the start, it was detached from the mainstream seventeenth-century cometary debates. There are no references to other theories in Guericke’s Experimenta nova, even though the author discussed various hypotheses on the system of the universe. ⁸⁹ Guericke did not pay much attention to the lists of similar opinions which Lubieniecki had sent him, and he discarded them with a brief answer only. It can be assumed – although we lack any direct statements to support it – that Guericke was to some extent proud of his cometary system and of its originality, especially given the fact that he supposed that he had discovered a method of predicting comets.

Guericke was right when he claimed that his cometary theory was original. Most of the seventeenth-century scholars considered comets to be celestial objects. This was the idea of Johannes Kepler who accepted the conclusions of Tycho Brahe’s observations of the comet of 1577. Kepler believed comets to be ephemeral objects in the Aether and to move in straight lines. ⁹⁰ René Descartes discussed the tailed stars in the context of his theory of vortices. In his opinion, when a star is entirely covered by sunspots, it loses its own vortex and degenerates into a planet or a comet. If it becomes the latter, it moves across another star’s vortices. ⁹¹ In Johannes Hevelius’s opinion, comets are disc-shaped exhalations from planetary atmospheres, especially from Saturn and Jupiter, and their paths are parabolic or hyperbolic. ⁹² This list is by no means comprehensive and these examples differ in their explanations of the nature of comets but they share a belief that comets belong to the heavens. ⁹³

Guericke’s cometary theory passed almost entirely unnoticed. Apart from Lubieniecki’s Theatrum cometicum, I could not find any other contemporary text which discussed it. And when the Experimenta nova were published, the short supplement about the comets probably did not spark much interest. The review of the Experimenta nova in the Philosophical Transactions discussed only Guericke’s views on space and the universe, and on his experiments with the vacuum. ⁹⁴ Also Lubieniecki’s correspondents did not pursue this topic in their works. In his letter to Lubieniecki, Hevelius stated that the theory is easy to refute but a brief letter is not a proper place to do it. ⁹⁵ Nevertheless, he did not mention Guericke’s views in his cometary books.

Conclusion

Guericke’s cometary theory turned out to be a dead end among cometary discussions of the seventeenth-century and his contemporaries considered it to be a mistake. Nevertheless, it was an interesting attempt to extrapolate some results of his studies onto other fields of natural philosophy and to link cometary theory with physical theory. Even though his theory was just an offspring of his main studies, Guericke tried to lay a solid foundation for his cometary considerations. He based not only on theoretical speculations but on his experiments as well. He believed that his anemoscope could be a real breakthrough in both meteorology and in astronomy as well.

Despite this fact, Guericke has seemingly never been much interested in comets. In his letters to Lubieniecki, he often declared his lack of interest to pursue this subject. Moreover, he did not summarize his cometary views and he only reprinted his letters which discussed them.

It might be concluded that Lubieniecki was more interested in Guericke’s cometary theory than the author himself. He eagerly wanted to learn more about it – either from Guericke who was prompted to give more details of his theory, or from his other correspondents who were encouraged to discuss this new idea. His desires, however, remained unfulfilled as he received very few replies, even from Guericke himself. Therefore, Lubieniecki soon lost interest in the theory. Nevertheless, it seems that Lubieniecki’s inquiries and letters could somehow affect Guericke’s cometary theory and made him reconsider the supernatural influence on winds and, by extension, comets. Moreover, Lubieniecki’s Theatrum cometicum is the only source of information about the theory and thanks to this book and Lubieniecki’s efforts, Guericke’s proposition has not been completely forgotten.