Geographia Magnetica
The Fifth Part of the Sixth Book of the Magnetic Art: Magnetic Geography
Kircher’s
Geographia Magnetica
Chapter on Magnetic Geology from Magnes sive de Arte Magnetica (1643)
Attributed to Boston College Libraries, public domain, via Internet Archive
Kircher’s magnetic geography was distinct in a world of wide and varied interest in geography. While previous scholars had created theories of various magnetic substances and variations in the Earth’s magnetic field, Kircher’s magnetism was an inherent and vital aspect of the make-up of the core of the Earth. With a lack of classical writing on magnetism, Kircher’s observations and experiments lead him to a theory of a dynamic and chaotic interior of the Earth, one not seen in previous writings and unique among other scholars who tended to believe in either a static interior or changes arising from celestial forces. Kircher’s world, while drawing from Aristotelian ideas of the four elements interacting to bring creative and destructive forces to the surface, also heavily relied upon magnetic threads running underneath the surface of the Earth. Ultimately, Kircher’s investigations into newly discovered magnetic phenomena demonstrated his usage of modern and scientific analytical tools, his Jesuit network and helped him to more firmly develop a theory of the Earth’s magnetism.
Kircher believed that the entire Earth was imbued with magnetic force, which was distributed linearly, from pole to pole. This is superficially similar to the modern understanding of the Earth’s magnetic field. The north-south polarity of the Earth’s magnetic field was quite well-known, as well as the existence of a true north and a magnetic north; there were observable fluctuations of north across the globe – both in latitudinal and longitudinal directions. Where a modern reader might imagine the magnetic field of the Earth as extending out from the surface of the Earth, Kircher’s conceptualization of the field was as “concentric layers like layers of an onion lying on top of one another but joined together at top and bottom”[1] lying below the Earth’s surface. The force came from the interior of the Earth itself, in the geological structure of the interiority of the Earth. This magnetic force did not arise from a separate piece or element of the Earth, and nor were loadstones a special element. Rather, the Earth had an inherent magnetic quality, one which imbued magnets with this magnetic force; “hence the Earth was the source of any magnetic force and the ultimate explanation of any magnetic phenomenon.”[2] Because loadstones were mined from deep in the Earth, he concluded that it was in this resting spot that they were given their magnetic qualities.
Kircher did not leave the question of the Earth’s magnetic quality a vague phenomenon, but described the internal structure of the Earth, expanding upon the various substances which formed the chaotic interior. His concept of the interior of the Earth was a series of chambers, where the basic Aristotelian elements of fire, earth, air, and water came into conflict with one another, and thus affected change in the mineral makeup of the world. For example, when fire and air chambers came together, they created an immense pressure, which was capable of both destroying and creating land. This change was observed on land most acutely in the form of volcanic eruptions. These forces and chambers were held together by strands of magnetic matter. When God created the Earth, Kircher believed that He laid strands of magnetic material in lines from pole to pole. When the Earth was first created, these fibers were all perfectly laid out from north to south. However, in time, as the creative and destructive forces inside the Earth created and destroyed new geological structures, the repositioning of mineral deposits disrupted and shifted these fibers. His conceptualization of the Earth’s interior and the origin of the Earth’s magnetic field was distinct among his contemporaries. The common understanding of the Earth’s interior was that it was orderly, with none of the chaos inherent in Kircher’s fibrous and shifting landscape. The concept of magnetic fibers, apart from a few of the scholars Kircher drew from, was unconventional: most scholars of the day believed in a celestial origin to magnetism, rather than the terrestrial origin Kircher described.[3]
Kircher arrived at this unique conclusion upon several experiments and observations of geography, which arose specifically from two puzzling features of the Earth’s magnetic field. These two issues were magnetic dip and magnetic variation and were new discoveries in the world of navigation. Magnetic dip was a phenomenon where a compass needle, when viewed horizontally, would dip below the edge of the compass. This had only been documented in the last hundred years, measured initially by English sailor Robert Norman in 1580. Gilbert, and subsequently Kircher, suggested that this could be used to determine latitude and longitude with the compass, a discovery which could have revolutionized navigation. In Magnes, Kircher endeavored to find the ratio between measured dip and latitude. He wrote “cum totus Telluris globus Magnetica virtue sit imbutus et vis et infie omnes partes suas, quibus integrator, in polos dirigendi,”[4] that because the entire globe of the Earth is imbued with magnetic virtue and since it possesses the power of directing all of its parts into the poles that – as he says further into the passage – an independent piece of iron placed in water at the equator would be angled perpendicularly to the Earth. Thus, one could theoretically measure the latitude based upon the angle of the needle of a compass-like device.
From this quote, a more spiritual element of his magnetic theory is made clear. The magnet held in itself the ability to restore order. It was this great terrestrial power, when applied to the entire Earth, which caused the magnetic dip because, as Kircher wrote, the constrained needle was attempting to right itself with the Earth’s magnetic pull, conforming itself to the terrestrial and world axis. This almost anthropomorphized ability of the magnet to restore and create order is a consistent and clear attribute which runs the entirety of Magnes. This particular attribute of the magnet was likely so attractive to Kircher, as bringing order out of chaos was God’s role in the story of creation. The Earth, as magnet, draws whichever unaligned element into its correct path, but the object itself is willing and eager to be directed as such. This mutual pull defines his concept of attraction, sympathy, and friendship, becoming a clear and conscious pull towards order and correctness.
Additionally, his theory, that the angle of the dip of a compass needle or magnetized iron depends upon its proximity to the poles of the Earth, suggested that it should be mathematically possible to determine a ratio between the angle of the iron and the position of the magnet on Earth. The discovery of this formula would have been an enormous gain to the world of navigation and Kircher promised in several correspondences and in Magnes itself that he would find the solution eventually. However, the eventual collected data would in and of itself be a feat for which several acquaintances would write to him to both contribute and applaud the effort.[5] To aid in his search, he utilized the network of Jesuit scholars all across Europe and the globe to measure the phenomenon in as many locations as possible. He collected measurements from Western and Eastern Europe, African coastal areas, the Caribbean and Florida, Brazil, Japan and the Pacific Islands. He also used reports from Dutch and English arctic expeditions.[6] While the measurements on land were fairly easy, the inherently unstable nature of the ocean made sea measurements incredibly difficult. Because the method of measurement was so delicate, the measurements sent to Kircher were highly inconsistent. In addition, there were inconsistencies and variations inherent in the structure of the Earth’s magnetic field which would have seemed like errors, even if the measurements were completely accurate. He was frustrated by the inability of the sailors to get consistent readings and stuck to the idea that if people would better follow his instructions, he would have been able to find a direct correlation.[7] Unfortunately for Kircher, this would be a problem he would not solve and it would continue to stump future scientists for years to come.
From his investigations into magnetic dip he did take something quite valuable – the network of Jesuits and secular scientists who were able to compile magnetic chart readings from all over the globe. Utilizing these contacts, Kircher was able to make more headway into another inconsistency in the strength of the Earth’s magnetic field, magnetic variation. Magnetic variation (or as it is more commonly known today, magnetic declination) is a term for how much the magnetic field in a particular place stray from true north. This was a more well-known and documented occurrence, but the magnitude of Kircher’s collected measurements were far beyond anything that had come before it. It was in his collection of data that he was able to demonstrate that magnetic variation in a single location could change over time – a happening that many contemporary scientists did not believe to be true. While this had been observed previously in London, Kircher was able to document the shift in several different locations. The mutability of the magnetic field would prove to be a key element of Kircher’s understanding of geology.
Before Kircher described in Magnes his theory of this cause in variation, he first disproved several popular ideas and explanations. One of the most popular, especially to explain why there was more variation at sea, was the existence of islands composed of magnetic materials. This, Kircher reasoned, would be impossible for two main reasons. Firstly, these islands did not seem to impact land readings at all and secondly, if their magnetic pull was strong enough to overcome that of the Earth, then one should be able to find such an island, yet none had been discovered. Other common conceptions he corrected were that these variations were due to either moving influences or intelligences in the heavens, or perhaps an unseen star. Kircher held that magnetism had a terrestrial origin, and that while stars may act on certain medicines in a magnetic manner, there was no natural magnetic force coming from the stars. This particular aspect of his magnetic philosophy will be discussed more in depth later in the paper. Finally, he was able to disprove the idea that magnetic variation was a function of longitude by the force of the amount of data he had collected which demonstrated that assumption was incorrect. Furthermore, as Kircher’s understanding of the Earth’s magnetic field relied upon a north-south polarity, the concept that the variation was due to a natural change in the Earth’s magnetic field without moving further north or south could not stand logically.[8]
One aspect of variation which became clear from the collected measurements – and which would be instrumental in Kircher’s development of his theory of the Earth’s interior – was that the variation was stronger at sea than on land. While previous scholars on magnetism had theorized magnetic variation was due to changes in landscape, such as mountain ranges, Kircher’s observations did not support this, instead indicating that there were more areas of variation over the sea, where such land structures did not exist. Kircher concluded that the strength over the ocean could be ascribed to subterraneous or submarine geological formations and mineral deposits. While this seemed similar to the idea of the cause as mountain ranges, Kircher’s explanation was that the ocean allowed for more magnetic force to reach the surface whereas land stifled the force, so variations were felt more acutely over the water.[9] This conclusion is an interesting one, considering that he had documented issues with the accuracy of measurements performed at sea due to the delicacy of the instruments. However, it is possible he decided these errors were insignificant in the face of his arguments of theory and personal experimentations.
He supported this conclusion with several suppositions and an experiment. The experiment was described in Magnes as follows: one placed several magnets in a basin and then covered them with water. Once submerged, a compass was held over each loadstone, and variations were noted. Each measurement should differ in accordance with the shape and purity of the loadstone. To Kircher, this proved that water did not significantly interfere with magnetic powers and would explain the greater influence on the sea where the ocean had “greater magnetic virtue than continental land masses which were exposed to air,”[10] that the ocean was a better conductor than solid land. Additionally, he had found that magnetic variation was common around islands. This was because islands were outcroppings of the ocean floor, and the chaotic and stronger magnetic elements were brought closer to the surface rather than land masses which were distinct from the ocean’s own mineral composition. This was partly due to Kircher’s other supposition that there were more irregular and stronger terrestrial variations on the ocean floor than at higher altitudes. He alluded that this was related to the fact that naturally occurring magnetic metals were found primarily in deep mines and the ocean floor, with all its magnetic affinity, was closer to the inherent fibers of magnetism than the land.[11]
Kircher believed in the terrestrial origin of magnetic force. The origin of magnetic influence was a topic of debate, but Kircher clearly laid out his understanding, as coming from fibers placed in the Earth during its creation. While these had been disrupted over time by internal chaos, accounting for magnetic variation across the globe, there was a base idea of the magnetic structure of the Earth as a system of orderly fibers which in turn enforced their structure upon the Earth’s iron. This conceptualization is rather reminiscent of the description of God’s creation, bringing order from chaos. Even with this scripturally inspired theory, Kircher’s rational approach to his investigations is clear, with him gathering data and basing theories off of this information, even while those ideas may have gone against the common knowledge of the day. While he did not adhere to a strict scientific method, he approached his investigations of these magnetic abnormalities with a blending of rational thought, Aristotelian concepts, and scripture-inspired theory.
[1]
Martha R. Baldwin, “Athanasius Kircher and the Magnetic Philosophy” (PhD diss., University of Chicago, 1987), 277.
[2]
Baldwin, The Magnetic Philosophy.
[3]
Ibid., 315.
[4]
Athanasius Kircher, Magnes Sive De Arte Magnetica Opus Tripartitum, 3rd ed. (Rome: B. Deversin, 1654), https://archive.org/details/KircherMagnesSive1654, 61.
[5]
John Fletcher. A Study of the Life and Works of Athanasius Kircher, ‘Germanus Incredibilis:’ With a Selection of his Unpublished Correspondence and an Annotated Translation of his Autobiography, ed. Elizabeth Fletcher (Leiden: Koninklijke Brill NV, 2011), 274.
[6]
Baldwin, The Magnetic Philosophy, 269.
[7]
Michael John Gorman, “The Angel and the Compass: Athanasius Kircher’s Magnetic Geography,” in Athanasius Kircher: The Last Man Who Knew Everything, ed. Paula Findlen (Oxfordshire: Routledge, 2004), 240-242.
[8]
Baldwin, The Magnetic Philosophy, 263-277.
[9]
Ibid., 276-278.
[10]
Ibid., 278.
[11]
Ibid., 280.