The mean free path of gas molecules in the transition r$eacute$gime

Comparison is made between the electrical and thermal conductivities of solids and the transport properties of gases, with special reference to boundary limiting effects. The transition from continuum to molecular behaviour of gases is explored using a modified mean free path. Relative intermolecular and boundary collisions are calculated and it is proposed that, by assuming the transport process to be partially continuum and partially molecular, according to such frequencies, there results a plausible account for some of the observed `anomalies' in gas flow characteristics in the transition régime.