  We present finite-differences time- domain calculations of the effective
permitivity of a periodic array of Cu strip wires that are an ingredient needed
in metamaterials for obtaining left-handed materials. We use the Cu frequency
dependent permitivity. The result is critically dependent of the wire
thickness. In particular for the wires of 0.003cm thickness used in
metamaterials experiments the imaginary part of the effective permitivity
dominates over the real part, which is slightly positive at 11GHz. Wires 10 -
20 times thicker may provided a good transparent left-handed material.
