In the 19th century scientists attempt various explanations of the incessant motion of small particles suspended in a liquid.

One possible explanation involves the collisions with atoms. But this explanation presupposes that the hypothesis that heat is nothing else than the motion of atoms is correct.

A confirmation of this hypothesis is expected from the measurement of the velocity of Brownian motion. It should be possible to calculate it from the atomistic theory of heat.

But the attempts to determine the velocity of Brownian motion fail.