I ran across this segment from a larger work. I have no idea if this is where the word usage of individuals as atoms might have come from, but found it interesting, from roughly that same time period (I think), and rather applicable to the Forsytes as I see them in the first few chapters. On the other hand, I may be totally off target. :-)

In London, every individual man revolves in two orbits: first, round his own axis in his individual sphere of action, be it little or great, narrow or widely extended; he revolves also with the huge mass of which he is but an atom, but which is, nevertheless, carried onwards in its course by the united exertion of aggregated atoms like himself.