four Clarke Chapman tri-drum coal-fired boilers. The high pressure sets were supplied with steam at 900 psi and 925 °F (62 bar and 496 °C) from three Babcock & Wilcox radiant open pass type coal-fired boilers (each 220,000 lb/hr, 27.7 kg/s) and from six Mitchell two-drum coal-fired boilers (also each 220,000 lb/hr). The East Bridge power station comprised two 6 MW turbo-alternators supplied with up to 120,000 lb/hr (15.1 kg/s) of steam from two Stirling coal-fired boilers. From 1958 all the electricity generated was sold in bulk to the Northern Ireland Joint Electricity Committee (NIJEC), supplies for distribution by Belfast Corporation were purchased from the NIJEC. In the year ending 31 March 1958 the Corporation exported 702,993 GWh to the NIJEC and purchased 541.750 GWh. Consumers were supplied with a range of electric current: 220–380, 230–400 and 450–500 Volt AC and 220 and 440 Volt DC, and 550 V DC for traction. The growth in electricity supply is demonstrated in the table. Londonderry Corporation Londonderry Corporation Electricity Department gained the authority to generate and sell electricity under the provisions of the Londonderry Electric Lighting Order 1891 confirmed by the Electric Lighting Orders Confirmation (No.3) Act 1891. Further powers were given by the Londonderry Corporation Act 1918. Electricity supplies commenced in May 1894. The corporation's supply area was 3.6 square miles with a population (in 1958) of 502,000. In 1958 the generating station comprised: two 1,000 kW Westinghouse, one 4,000 kW and two 6,000 kW Metropolitan Vickers turbo-alternators. There were also six rotary converters for the DC supply. The turbo-alternators were supplied with steam from two Babcock & Wilcox and four Yarrow coal-fired boilers. Consumer supplies were 220–440 Volts DC and 220–380 Volts AC. The electricity supply from the mid-1950s is shown in the table. Electricity Board for Northern Ireland The Electricity Board for Northern Ireland was established in 1931 under the provisions of the Electricity (Supply) Act (Northern Ireland) 1931. Its duty was to co-ordinate and improve the supply, distribution and sale of electricity. The board's area of supply was 5,200 square miles, with a population of 825,000 and 208,000 premises. Several electricity development schemes were scheduled in the 1931 Act. For example, the first scheme included most of County Down and County Armagh and part of County Tyrone. The schemes culminated in an eighth scheme authorised in June 1947 to cover all remaining parts of Northern Ireland. Under the