Voltages observed between the ends of various underwater telegraph cables up to 9660 km long are analyzed in terms of planetary electric fields, deep ocean tides, wind driven surface currents, and geomagnetic induction.It is concluded that the average planetary electric field, which may originate from the internal processes generating the geomagnetic field, is not more than 0.038 mv/km ± 20% between Fiji and Vancouver Island. This is almost an order of magnitude less than previously reported.The average resistivity of the sea bed to a scale depth of 130 ± 20 km, treated as a single homogeneous plane layer, is 37 ± 5 ?m off the coast of Vancouver Island. This is similar to what is observed below the adjacent land.No statistically significant model was found relating the voltages on the 9660 km cable to tide heights at the shore, and geomagnetic field changes. However, it was found that the geomagnetically induced voltages between the ends of the 85 and 23 km cables were larger than the tidally induced voltages. A satisfactory model of these cable voltages was developed in terms of tidal heights, measured at the shore, and geomagnetic fields measured at a nearby observatory.All the cables were broken at sea, and the data are therefore of special interest because it is unlikely they will ever be duplicated.