  We observe simultaneously the Ca II K, Ca II 8542 and H-beta emissions in
solar prominences at high spatial and spectral resolution. We confirm a
branching in the emission relations of Ca II and H-beta. This is related to
non-thermal line broadening, which affects the Ca II lines much more than
H-beta. The classical non-thermal (Maxwell) line broadening, determined by
comparison of the width of hydrogen lines with those from calcium lines, is not
sufficient to explain the Ca II widths. This indicates an additional broadening
by large-scale motions of the unresolved prominence fine-structure.
