High-resolution observations suggest that quiescent solar prominences are m
ade of small-scale fibrils stacked one after another in both the vertical a
nd horizontal directions. These fibrils are interpreted as the cool, higher
most part of much larger coronal loops which are rooted in the solar photos
phere. On the other hand, there is some evidence showing that small amplitu
de oscillations in prominences can affect individual or groups of fibrils,
which vibrate with their own periods. Using a simple magnetostatic model to
represent the fibril structure of quiescent solar prominences, Joarder et
al. (1997) investigated some oscillatory properties of the Alfven and fast
magnetohydrodynamic modes. In this paper, with a proper treatment of bounda
ry conditions, we reexamine their configuration and explore more deeply the
basic features (mainly frequency and spatial structure) of the fast mode.
The main conclusion is that, for reasonable values of the fibril's width, p
erturbations extend far away from its axis and, therefore, a single oscilla
ting fibril can excite oscillations in neighbouring ones.