Various processes have been proposed to explain how galaxy discs acquire
their thickness. A simple diagnostic for ascertaining this ``heating''
mechanism is provided by the ratio of the vertical to radial velocity
dispersion components. In a previous paper we have developed a technique for
measuring this ratio, and demonstrated its viability on the Sb system NGC 488.
Here we present follow-up observations of the morphologically similar Sab
galaxy NGC 2985, still only the second galaxy for which this ratio has been
determined outside of the solar neighbourhood. The result is consistent with
simple disc heating models which predict ratios of σz/σR less
than oneComment: 5 pages, 4 figures. Accepted for publication in MNRA