Science Art: Fig. 2 – Slit Mechanism from “The Scattering of Hydrogen Positive Rays, and the Existence of a Powerful Field of Force in the Hydrogen Molecule” by G. Thompson in Philosophical Transactions of the Royal Society of London

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I looked for molecules in Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character (1905-1934), and this is what I found. It’s a device designed by Mr. William S. Farren, M.A., for observing “the positive rays” as they scatter through a chamber filled with hydrogen gas.

And that’s how we know what’s inside atoms.