What did Brown do?

Brown did not discover Brownian motion but did do something remarkable in that he established, to his surprise, the universality of the phenomenon. Brown's contribution changed the problem of erratic motion from a biology problem to a physics problem. While his famous 1828 paper is often referenced, there were several criticisms made of it after its publication, which he defended and clarified in a paper a year later, in 1829. We review this early history and what his contributions were.