  Temperature-dependent inter-plane resistivity, $\rho _c(T)$, was used to
characterise the normal state of the iron-arsenide superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ over a broad doping range $0\leq x<0.50$. The
data were compared with in-plane resistivity, $\rho _a(T)$, and magnetic
susceptibility, $\chi (T)$, taken in $H \bot c$, as well as Co NMR Knight
shift, $^{59}K$, and spin relaxation rate, $1/T_1T$. The inter-plane
resistivity data show a clear correlation with the NMR Knight shift, assigned
to the formation of the pseudo-gap. Evolution of $\rho _c(T)$ with doping
reveals two characteristic energy scales. The temperature of the cross-over
from non-metallic, increasing on cooling, behavior of $\rho _c(T)$ at
high-temperatures to metallic behavior at low temperatures, $T^*$, correlates
well with an anomaly in all three magnetic measurements. This characteristic
temperature, equal to approximately 200~K in the parent compound, $x$=0,
decreases with doping and vanishes near $x^* \approx$0.25. For doping levels $x
\geq 0.166$, an additional feature appears above $T^*$, with metallic behavior
of $\rho _c (T)$ found above the low-temperature resistivity increase. The
characteristic temperature of this charge-gap formation, $T_{\rm CG}$, vanishes
at $x_{\rm CG} \simeq$0.30, paving the way to metallic, $T$-linear, $\rho_c
(T)$ close to $x_{\rm CG}$ and super-linear $T$-dependence for $x>x_{\rm CG}$.
None of these features are evident in the in-plane resistivity $\rho_a(T)$. For
doping levels $x <x_{\rm CG}$, $\chi (T)$ shows a known, anomalous, $T$-linear
dependence, which disappears for $x>x_{\rm CG}$.
