  We present measurements on one-dimensional Josephson junction arrays formed
by a chain of SQUID loops in the regime where $E_J / E_c\simeq 1$. We observe a
blockaded zero current branch for small bias voltages. Above a certain voltage
$V_\mathrm{sw}$ the $I$-$V$ characteristics changes discontinuously to a
dissipative branch characterized by a flux dependent conductance. Three of four
samples show a pronounced hysteresis for a forward and backward voltage sweep.
We observe a periodic field dependence of the conductance above $V_\mathrm{sw}$
which can be described with $P(E)$ theory for cooper-pairs and therefore gives
evidence of viscous dynamics of Cooper pair transport through the array.
