Within a gas, the various molecules travel at different velocities, but it is not easy to know what these are. James Clerk Maxwell calculated theoretically the relative probabilities of these speeds, which are lopsided in favour of higher speeds: while the greatest number of particles travel relatively slowly, the highest possible speed is much further away from this than is the slowest speed. This theory was then developed further, with greater substantiation, in 1868, by the Austrian physicist Ludwig Boltzmann, and the Maxwell-Boltzmann distribution of molecular speeds is named after these two scientists.
Editors. "Distribution law of molecular velocities stated by Maxwell". The Literary Encyclopedia. First published 30 August 2013
[http://www.litencyc.com/php/stopics.php?rec=true&UID=6319, accessed 30 November 2015.]