My Writings on William Gilbert
I have written a number of posts about William Gilbert (1544-1603) and his book De Magnete [On the Magnet], the first systematic study of magnetism. I was having difficulty keeping track of my own writings, and have therefore prepared a summary thereof, which I have organized into different categories. If I write more, I will add more entries to this post.
Introduction
In De Magnete, Gilbert conducts a number of experiments with a mini-Earth, which he calls a terrella, which he makes out of lodestone, a natural magnetic material. I did some etymological work to figure out what a mini-Sun should be called: a sollelus.
Gilbert was a strong proponent of using experimental methods to determine the truth of statements about physical phenomena. His book has been called the first work in experimental physics.
Book One
The first book of De Magnete focuses on loadstone, where it is to be found and what makes it up; in particular, iron is always present, and when smelted, loadstones make the best steel. Loadstones always have north and south poles, and can be used to make compasses. As the Europeans learnt about open-ocean sailing, they learnt that compasses do not always point true north, but deviate.
Book One, part 1: William Gilbert Writes about the Loadstone
Gilbert was writing when alchemy had yet to be replaced by chemistry. Since loadstones, in the form of terrellae, acted like a mini-Earth, he posited that iron formed an integral part of the Earth. Furthermore, for him, loadstones can be considered to be animate, and so cannot be made up of the element “Earth”, one of Aristotle’s four elements (Earth, Air, Water and Fire); for Gilbert, Aristotle’s “Earth” is lifeless.
Book One, part 2: William Gilbert Examines Iron, Calls Aristotle’s Earth Element Dead
Book Two
The second book focuses on the properties of loadstones. First, he makes it clear that “electric bodies”, which attract when rubbed, are of a completely nature to “magnetic bodies”. Gilbert argues that magnetic attraction, in which the south pole of one body is attracted to the north pole of another body, is a form of coupling. Electric attraction is of a different nature, and seems to involve some material being exchanged between mutually attracting bodies.
Book Two, part 1: William Gilbert Compares Electric Bodies to Magnetic Bodies
Unlike electric bodies, magnetic bodies continue to repel or attract each other even when, for example, a flame is placed between them. He also claims that when two magnetic bodies repel or attract each other, all of the material in each body is participating in the repulsion or attraction. Furthermore, when iron is placed in contact with a magnet, the whole acts as a larger magnet.
Book Two, part 2: William Gilbert Discusses Magnetic Bodies
Gilbert considers how the attraction of a piece of iron by a terrella varies according to where that piece of iron is placed. His experiments seem to demonstrate that the attraction varies according to how much of the terrene material is participating in the attraction, and that this reaches a maximum near the poles.
Book Two, part 3: William Gilbert Considers the Internal Structure of the Terrella
Gilbert conducts a number of experiments with terrellae and pieces of iron, arranging them in different geometrical arrangements. He concludes that these are interacting in a similar manner to how the Moon and the Earth interact, for these two celestial bodies are made up of the same terrene matter, and that likely this is the cause of the tides.
Book Two, part 4: William Gilbert States that the Moon Causes the Tides
It turns out that the capping of a loadstone with an iron sheet strengthens it, as does the chaining of multiple loadstones.
Book Two, part 5: William Gilbert Aligns Several Loadstones
Book Three
Each magnetic body has its own north pole, south pole, equator, meridians and parallels. Gilbert examines what happens to these when a magnetic body is cut into two, and how each of the resulting bodies ends up its own poles, equator, meridians and parallels, and how these interact when the bodies are brought together. He explains how this verticity can be created artificially, for example by burying iron in the earth aligned north-south for an extended period of time, or by rubbing a needle with the pole of a magnetized body.
Book Three, part 1: William Gilbert Explains How Magnetic Bodies Acquire Direction
Gilbert experiments with needles brought close to a terrella, near or far from the poles, as individual needles or as pairs.
Book Three, part 2: William Gilbert Shows the Direction of Compass Needles
Book Four
Gilbert was conducting his experiments at a time when the European nations were exploring the globe. The deviation of the compass needle from true north, and the variation in said deviation, as ships sailed in different parts of the world, limited the utility of compasses as navigation tools. His understanding was that since it was the iron in the Earth that was the basis for magnetism, that the presence of a continent would deviate compass needles. He noted that east of Novaya Zemlya, there is no such deviation, as there is west of Europe; as a result, he predicted the presence of the Northeast Passage almost three centuries before its sailing by Adolf Erik Nordenskïold (1832-1901).
Book Five
Gilbert presents a mathematical model of how the magnetic dip varies with latitude.
Book Five, part 1: William Gilbert Calculates the Magnetic Dip
Gilbert argues that the earth is animate, and has a soul, and that it allows life to exist thereon.
Book Five, part 2: William Gilbert Calls the Earth Animate
Book Six
Gilbert argues that it is the magnetic nature of the Earth that allows its diurnal motion, and that it is the annual rotation of the Earth around the Sun, with the tilted axis of the Earth, that allows civilization thereon.
Book Six: William Gilbert Supports Copernicus
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Have you seen Brent shadbolt’s substack, it kind of reminds me of yours. Personally I do not have the knowledge to evaluate anything but he had an interesting article about cosmic background radiation.
Mindblowing! Incredible! Hey, did he know Francis Bacon? Or Thomas Heriot?