Results are presented from a study of jet production in ppBAR interactions with square-root s = 630 GeV at the CERN SppS-ColliderBAR, which are tagged by a proton or antiproton which possesses more than 90% of the incident beam momentum. The hard scattering which occurs between a parton in a beam particle and another in the soft residual component (pomeron-dominated) of the tagged proton allows the pomeron's partonic structure to be investigated. The observed jet distributions are in good agreement with expectations for hard parton-parton scattering in QCD. The pomeron exhibits a hard structure like 1 - x. However, there is an additional significant (30%) delta-function-like component, in which the entire momentum of the pomeron seems to participate in the hard scattering.