  We perform integrated spectroscopy of 24 Galactic globular clusters. Spectra
are observed from one core radius for each cluster with a high wavelength
resolution of ~2.0 A FWHM. In combination with two existing data sets from
Puzia et al. (2002) and Schiavon et al. (2005), we construct a large database
of Lick spectral indices for a total of 53 Galactic globular clusters with a
wide range of metallicities, -2.4 < [Fe/H] < 0.1, and various horizontal-branch
morphologies. The empirical index-to-metallicity conversion relationships are
provided for the 20 Lick indices for the use of deriving metallicities for
remote, unresolved stellar systems.
