  So far, six mechanisms have been proposed to account for the Galactic disk
heating. Of these, the most important appear to be a combination of scattering
of stars by molecular clouds and by spiral arms. We study a further mechanism,
namely, the repeated disk impact of the original Galactic Globular Cluster
population up to the present. We find that Globular Clusters could have
contributed at most a small fraction of the current vertical energy of the
disk, as they could heat the whole disk to {$\sigma $}$_{z}$ = 5.5kms$^{{\rm -}
{\rm 1}}$ (c.f. the observed 18 and 39 kms$^{{\rm -} {\rm 1}}$ for the thick
and thin disks respectively). We find that the rate of rise of disk heat
($\alpha$=0.22 in \textit{$\sigma $}$_{z}$ $\sim t^{\alpha}$ with \textit t
being time), is close to that found for scattering by molecular clouds.

Astrophysics of Galaxies