Published online by Cambridge University Press: 23 December 2005
Effective temperatures of 30 turnoff stars with $-3.2 {<}$[Fe/H]${<}{-}1.5$ have been derived from the profiles of Balmer lines in high S/N, VLT/UVES spectra. While the systematic error of $T_{\rm eff}$ may be of the order of 100K, the differential values of $T_{\rm eff}$ are determined with a one-sigma precision of ${\sim}25$K. These precise $T_{\rm eff}$ values are used in a study of the slope and dispersion of the Li abundance as a function of [Fe/H]. A small, but significant cosmic dispersion in $A$(Li) appears to be present exemplified by the two very metal-poor stars G64-12 and G64-37.