In a cold plasma, finite magnetosonic disturbances lead to the familiar steady‐state solitary pulse of Adlam and Allen. Leading effects of finite plasma pressure on these disturbances are considered using both linear and nonlinear analyses. Earlier limitations imposed by adiabatic considerations have been removed. Within a regime of limited disturbance strength the inclusion of finite temperature leads to a singular perturbation scheme. The nature of pulse distortions due to these effects is discussed both analytically and numerically.