  According to Klein (1973)  Boltzmann seemed to have been satisfied with his treatments of 1871 and 1872 and turned his attention to other matters for a couple of years. He did come back to gas theory in 1875 to discuss an extension of the Boltzmann equation to gases subjected to external forces. But this paper does not present any fundamental changes of thought. However, the 1875 paper did contain a result which, two years later, led to a debate with Loschmidt. It showed that a gas in equilibrium in an external force field (such as the earth's gravity) should have a uniform temperature, and therefore, the same average kinetic energy at all heights. This conclusion conflicted with the intuition that rising molecules must do work against the gravitational field, and pay for this by having a lower kinetic energy at greater heights.