The data set comprises continuous hourly recordings of electrical potential across the Dover Strait, which relate to the flux of water, over the period 1955-1965 and part of 1968-1969, together with parallel measurements of sea temperature and pressure. Voltages on telegraph cables were measured almost continuously by pen recording milliammeters installed at Dover since 1954. The d.c. potential between the inner conductor of the cable and its screen is measured through a 2.2 kohm resistor in series with a milliammeter, whose internal resistance was of order 1 kohm. The screen was earthed at both the English and French ends, and at the French end the conductor is also effectively earthed (through inductive elements) as far as low frequency voltage variations were concerned. Thus the voltage recorded at St. Margaret's Bay is effectively the difference in earth potentials between the particular coastal points in England and France. A 0.003F capacitance in parallel with the milliammeter shunted out voltage variations with time scales less than about half a minute. For calibration, a standard voltage cell was switched in place of the cable on occasions. For parallel measurements of sea temperature (related to conductivity) and local wind conditions, 6-hourly temperatures and barometric pressures from the Noord Hinder Light Vessel, the pressures from the Terschellinger Bank Light Vessel and the 6-hourly pressures from Gorlston (East Anglia) were used. Data for sea salinity at the Varne Light Vessel were extracted from International Council for the Exploration of the Sea (ICES) publications.