In 1886, Ferrel postulated that observed amplifications in the annual variation of MSL pressure for elevated stations are primarily due to differences between annual variations in temperature observed at land stations and the actual variations that would be observed in free air in the absence of a mountain or plateau. He introduced the so-called plateau correction to account for this effect. The Smithsonian tables represent the correction in Ferrel's original form as a pressure correction that is linearly proportional to the product of the station elevation and the deviation of the station virtual temperature from its annual mean. In Canada, the plateau correction is applied as recommended in the WBAN directly as a correction to the mean virtual temperature in the dry-air hypsometric equation in the form of a function, F, of the 12-hour mean station temperature. In Canada, F is expressed as a simple quadratic, is determined uniquely for each station and is applied at elevations both above and below 305 gpm. Based on the climatology of 300 Canadian stations, we present the results of a mathematical and geographical comparison of these methods and discuss the possible sources of discontinuity in MSL pressure fields across national borders.