The closed feed system for boiler plant, now the standard method, was developed in 1925 in order to reduce the oxygen content of the feed water.

Small turbine work took on a new aspect in 1927 when the self-contained type, all on one floor with auxiliaries driven from the main shaft, was introduced. This design, the result of efforts to save space on marine installations, did away with the usual basement and independent auxiliaries and was preferable on all counts— installation cost, starting, efficiency, and reliability. Though the principle was soon taken up by other manufacturers M-V has kept its lead, having made nearly five hundred self-contained sets to date.

The post-war reduction in shipbuilding speedily affected the Company's position in the marine propulsion field, though in 1919 two 9000-hp turbines with floating frame gears were ordered for s.s. Cuba, and fourteen similar ships were equipped. Two Japanese ferryboats were each fitted with two 3000-hp geared propulsion turbines in 1921.

Very high efficiencies were obtained on turbo blowers, of which some single flow units with 48-in impellers were ordered in 1928: the official tests on the first of these gave a record adiabatic efficiency, 7.97 per cent above the guaranteed figure.

For electric winders where the supply system could not cope with large peak demands, an important development was a turbo-electric scheme invented by A. Stubbs and J. F. Perry in 1924. This proved useful later on sinking winders in South Africa, where it must be possible to raise the men from the shaft even though current is cut off by lightning disturbances. In the Stubbs-Perry system the d.c. Ward-Leonard generator is geared to a high-speed steam turbine, and the flywheel effect enables the steam demand to be limited to, say, 15 per cent above the average over the winding cycle; collieries with their own boiler plant can thus obtain the advantages of electric winding.

In 1927 the turbine shops carried out a remarkable piece of engineering work outside their usual line. This was the construction of two large and highly complicated bottle-making machines designed by a solicitor, who was also a director of John Walker & Sons, Ltd., proprietors of the famous whisky. Each machine weighed about 40 tons, measured 17 feet in diameter by 15 feet high, and had fifteen operating heads. As the whole mechanism rotated at six revolutions a minute, a cam-and-lever system caused each head to go through a complete series of operations from drawing molten glass into a mould to ejecting a finished bottle. Using dual moulds, over a million pint-bottles could be made in a week.

GENERATORS
Electrical development in turbo-generating plant kept pace with the mechanical end. Machines made in three successive years, culminating in 1921 in a 20,000-kVA unit for Sydney, held pride of place as the largest 3000-r.p.m. generators in the world. The increase in sizes made it