  Perrin stressed the extent to which the value for Avogadro’s number yielded by his experiments on density distribution formed the basis of a strong argument from coincidence for the kinetic theory. Perrin posed the question of what density distribution of Brownian particles might have been suspected prior to his experiments if the kinetic theory is ignored. Since the particles were denser than the liquid in which they were suspended, a reasonable assumption might be that the particles fall to the bottom so that the density distribution is zero. This experimental result, substituted into Perrin’s formula, would have led to an infinitely large value for N. Another plausible assumption might have attributed an even distribution to the suspended particles. Such an outcome would have led to a value of zero for N. A decrease in density with height yields some value in between these two extremes. Prior to the experiment, then, the range of plausible results to be expected from feeding the measured distribution into Perrin's equation, derived on the basis of the kinetic theory, is immense. And yet the outcome was a number very close to that predicted by the kinetic theory.