364 SECTIONAL TRANSACTIONS.— G. 



application, and consequent expansion, of electric supply upon the development of 

 South Africa. 



Modem developments in steam turbine design have been in the direction of 

 increased output per unit, and increased fuel economy -with higher steam pressures 

 and temperatures, regenerative heating of the feed water, air pre-heaters and 

 economisers, and the use of re-superheated steam after partial expansion. 



The maximum blade annulus for a given speed of revolution has increased about 

 ninefold during the past twenty years, and the output in rather greater ratio than 

 this ; at 1,500 revolutions an efiBcient turbine with a double-ended low-pressure 

 stage can now be made with an output of 100,000 kw., and by arranging triple low- 

 pressure stages in a tandem cylinder turbine 150,000 kw. can be obtained from a 

 single unit. 



Modem improvements in the design of surface condensers are in the direction of 

 greater attention to the distribution of the steam among the tubes with the object 

 of obtaining high vacuum, hot condensate and air-free feed water. 



The paper proceeds to discuss progress in high-speed alternator construction. 

 The maximum output of such alternators for a given rate of revolution has increased 

 nearly fourfold during the last decade. For instance, at 3,000 r.p.m. the increase is 

 from about 10,000 kw. to 40,000 kw. The largest alternator output at 1,500 r.p.m. 

 obtainable at present is about 150,000 kw., coinciding with the maximum obtainable 

 from a steam turbine at the same speed. 



For alternators of large output the author advocates direct generation at higher 

 voltages, such as 33,000 instead of the 6,000-11,000 volts usual at the present day, 

 and gives arguments in support of higher voltages. 



A section of the paper is devoted to the subject of the strength and reUabUity of 

 large steel forgings for turbine shafts and alternator rotors. A new method of casting 

 ingots is described, employing a mould of which the horizontal dimensions are greater 

 than the vertical, the top and sides being maintained hot, so that the metal is cooled 

 from the bottom upwards with more or less horizontal planes of soUdification. This 

 obviates the structural weaknesses incidental to the usual metliod, and enables ingots 

 of the largest size to be cast with substantially uniform composition. 



Photographs of etched central sections of two ingots, one cast by the usual method 

 and one cast by the new method are shown for comparison. 



The paper then turns to a brief discussion of recent progress in marine turbine 

 installations, describing the latest arrangement of geared turbines with improvements 

 in economy obtained as the result of higher pressures and temperatures, and giving 

 a table of record fuel consumptions obtained from recent oil-fuel-buming steamships. 



In conclusion, figures are given indicating the progress of high-pressure and high- 

 temperature marine installations buUt or under construction in the Navy and the 

 Merchant Service, foUowiag the pioneer experiment with the Clyde River steamer 

 King George V. 



Mr. Beenaed Peice. — Compressed Air Supply on the Rand. 



Prof. G. A. Watermeyer and Mr. S. N. Hoffenberg. — A R svmc of 

 Mining Operations on the Rand. 



Thursday, August 1. 



Presidential Address by Prof. F. C. Lea on Science and Engineering, 

 (See p. 138.) 



Electrical Peoblems : — 



(a) Mr. C. H. Merz.- — The National Scheme for Electricity Supply in Great 

 Britain. 



After a brief historical survey of the development of electrical distribution and the 

 extension of areas covered by supply undertakings, the paper deals with the reasons 

 which led to the appointment of the Weir Committee in 1925. Previous experience 

 having shown the need for compulsory powers if the interconnection of the various 

 generating stations and networks of the country was to be brought about, the 



