Telegraph cables, shown here in cross section, were 26 millimetres in diameter. Seven strands of copper conductor carried electrical impulses that translated into telegraph messages. The copper was insulated by a natural latex called gutta percha, two layers of jute fibre, steel, and another two layers of jute. The exterior layer was a protective covering of steel reinforcing coil. Although the cable laid between New Zealand and Australia in 1876 held up well, the Cook Strait cable was frequently out of action because it was scoured by strong tides. In 1880 a second, longer cable was laid under calmer waters, from Cable Bay to Whanganui – a distance of 202 kilometres. This is a cross-section of an early Cook Strait cable.