  Magnetic relaxation in the Bragg-glass phase of overdoped Bi_2Sr_2CaCu_2O_8
crystals was investigated using time-resolved magneto-optical visualisation of
the flux distribution. This has permitted us to extract the current-voltage
characteristic, which can be well described by a power-law, although fits to a
stretched exponential E \sim \exp(- j_{c} / j)^{\mu} with 0.3 < \mu < 0.8 are
possible at long times in excess of 100 s.
