25 tion motors which drive the mill tandem. The complete installation was made by an American company that has had considerable ex- perience in electrifying sugar mills in Cuba. The feasibility of complete electrical operation in a sugar mill having been proved, other mills became interested. At the end of 1929 three more mills had completed their electrical installations. These mills were all equipped by a German company, which obtained the bids by offering lower prices and longer terms than its American sompetitor. Details of the three mills which were electrified during 1928-29 are as follows: Quear mill Bedadreng....cocoeann SoIMBOrO. anes sans annans OenSENERAT maemo Capacity of generators Current 1,350 kilovolt amperes_............. Alternating... saci Ousva peammmmanpenmrme pms ogin wid 1,000 kilowatts oo oooocaeooanaan. directo... ,600 kilovolt amperes... _......... \lternating... L000 kilowatts. ooceooeeooaeooooo. Directo... #00 kilovolt amperes....-....._..| Alternating. ..| »Y 1,600 kilovolt amperes... __..do....._._. 3v 1,000 kilowatts. .o.oomeoooooo) Directo... Ty 19 kilowatts ooo eceonyeee On 4by7 Bos emoeeaion aR en »y 100 kilovolt amperes..........} Alternating... yy 4 kilowatts. _ mcemmeeee Directo... Voltage | Prime mover 100/23 100/231 160/225 180/220 160/225 120/990 Steam turbine, Do. Do. Do. Do. Do. Do. Do. Motor. Do. Diesel motor. Motor. 160/320 230 230 270/380 290 it is probable that other additional Java sugar mills will install slectrical equipment, particularly if experience proves that lower operating costs result from such installations. With world sugar prices at their present levels the argument of economy of operation will have a strong appeal. This same price situation, however, may result in ducking the tendency to invest in expensive new equipment until conditions improve. MINING INDUSTRY Coal mining. —FElectrical energy is used extensively in the Govern- ment owned and operated coal mines in Sumatra, the total installed capacity of the mines being 9,350 kilowatts. - At the Ombilin coal mines on the west coast, three steam turbines, one A. E. G. of 2,750 horsepower capacity and two Stork machines of 2,500 horsepower each are installed. The A. E. G. turbine is connected to a generator of the same make, while Smit generators of 2,000-kilowatt capacity each are connected to the Stork turbines. The current is used chiefly to operate the direct-current locomotives which carry the coal in the mines and for operating ventilators and electrically driven air com- pressors, as well as for general lighting purposes. Prior to 1921 the motive power for the Poeloe Laoet mines was generated by steam, but this was not entirely satisfactory and two turbogenerators of 1,000-kilowatt capacity each have been installed. In 1927 a further addition was made when another unit of 1,000- kilowatt capacity was added. The three steam turbines are Stork machines and are coupled to Smit generators. The electric installa- tion at Poeloe Laoet made it possible to operate with electric motors their pumps of 2 to 4 cubic meters per minute capacity, the lifts, and the ventilators. An air-compressor plant for the operation of the pneumatic-drilling machinery, with an air capacity of 3,000 cubic meters per hour, is also operated by the power generated in the electric plant.