An analogy between the vortex and spin glass is examined by the determ
ination of the melting temperature T-m of the vortex glass by ac susce
ptibility for a melt-textured growth YBa2Cu3O7 bulk sample. The meltin
g line T-m(B) is determined and obeys a power law: B proportional to (
1-t)(beta) with beta=1.57, where t=T-m/T-c is the reduced temperature.