# Did Maxwell originally write his equations using quaternions?

I read somewhere, some time ago that Maxwell originally wrote his eponymous equations using the formalism of quaternions and it was only the later intervention of Gibbs and Heaviside that put them into the modern form, that is via vector analysis.

Is this true? And if true, how many equations were there in that formalism?

I read somewhere, some time ago that Maxwell originally wrote his eponymous equations using the formalism of quaternions ... Is this true?

It seems that the answer is "Not quite". Maxwell originally wrote his equations in components, and later simplified them by using quaternions and some vector calculus. It is true that Heaviside and Gibbs put them into their modern form.

And if true, how many equations were there in that formalism?

My source says 20. I count 12, but it says that "cont. eq. missing here", so maybe there were 8 equations relating to continuity.

Source: slides from the presentation On the changing form of Maxwell’s equations during the last 150 years — spotlights on the history of classical electrodynamics by Friedrich W. Hehl.

Maxwell's equations as they are expressed today, with modern vector notation and not Maxwell's quaternion notation, were first written by Oliver Heaviside in a few papers in the mid- to late 1880s, but it wasn't until 1893 that the first volume of his Electromagnetic Theory appeared (and vol. 2 in 1899 and vol. 3 in 1912).

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