In his celebrated papers on what we now term Brownian motion,1 botanist Robert Brown studied microscopic components of plants and deduced that their incessant stochastic motion was an innate physical feature not associated with their biological origins. The observations required that he study extremely small drops of fluid, which presented experimental difficulties. One of the most significant issues, discussed at some length in his second paper, was the effect of evaporation. Of those small drops he said, “It may here be remarked, that those currents from centre to circumference, at first hardly perceptible, then more obvious, and at last very rapid, which constantly exist in drops exposed to the air, and disturb or entirely overcome the proper motion of the particles, are wholly prevented in drops of small size immersed in oil,—a fact which, however, is only apparent in those drops that are flattened, in consequence of being nearly...

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