  The optical birefringence of rod-like nematogens (7CB, 8CB), imbibed in
parallel silica channels with 10 nm diameter and 300 micrometer length, is
measured and compared to the thermotropic bulk behavior. The orientational
order of the confined liquid crystals, quantified by the uniaxial nematic
ordering parameter, evolves continuously between paranematic and nematic
states, in contrast to the discontinuous isotropic-to-nematic bulk phase
transitions. A Landau-de Gennes model reveals that the strength of the
orientational ordering fields, imposed by the silica walls, is beyond a
critical threshold, that separates discontinuous from continuous
paranematic-to-nematic behavior. Quenched disorder effects, attributable to
wall irregularities, leave the transition temperatures affected only
marginally, despite the strong ordering fields in the channels.
