26 
The Boekit-Asam coal mines, which were opened in 1919, also use 
electric power, two A. E. G. steam turbines and generators, each of 
1,250 kilowatts capacity having been installed in 1924. 
Since the important coal mines in the territory already have elec- 
trical equipment, any further business in this field will necessarily 
take the form of renewals and: extensions. 
Tin mining. —Electric power is used extensively by Government 
and private interests in the extraction of tin on the islands of Banka 
and Billiton. On Banka the mines are entirely Government owned 
and operated. They obtain their power from the Government sta- 
tion at Mantoeng, where six Stork stesm turbines developing 2,500 
horsepower each operate a similar number of generators manufac- 
tured by the Dutch firm, Willem Smit & Co., having a total capacity 
of 12,000 kilowatts. The first installation was made in 1919 and con- 
sisted of two 2,500-horsepower steam turbines and two 2,000-kilowatt 
generators. Four additional installations have been made since then, 
and at present the mines are completely electrified. A still further 
increase in the central power station is now under consideration. 
The mines operated by the Gemeenshappelijke Mijnbouw Maats- 
chappij Billiton are also using electric power obtained from 8 central 
station at Manggar, which is claimed to be the second largest Diesel 
installation in the world. The plant at Manggar was first opened in 
1914, when three Werkspoor Diesel motors and three Siemens- 
Schuckert motors, having a total generating capacity of 3,300 kilo- 
watts, were installed. The plant has been enlarged from time to 
time until the present capacity is now about 8,700 kilowatts. 
Electrical energy is used chiefly by the above mines in connection 
with the operation of suction pumps of 200 and 250 horsepower, and 
other small motors. As early as 1921 the Banka tin mines were 
using approximately 40 electric motors aggregating over 1,300 horse- 
power. Asin the case of electric power used in coal mining, new busi- 
ness in this field is limited to renewals and extensions of existing 
facilities. 
RUBBER INDUSTRY 
With few exceptions, all of the European rubber estates in the 
Netherland East Indies are using electrical energy of some descrip- 
tion for power or lighting purposes. Few of the estates are obtaining 
their electric supply from the public-utility companies, as the latter's 
transmission lines have not yet been extended to the localities where 
rubber estates are situated. 
In the rubber factories electric power is used chiefly for driving the 
machines which press the coagulated latex into sheets. Electrically 
driven machines are also used to macerate the coagulum and produce 
crépe or to clean and process scrap rubber. These machines are 
little more than a set of two steel or cast-iron rollers, which are driven 
by a prime mover of some description, commonly a Diesel or a steam 
engine. But estates with ample electric power available are now 
using motors. Motors of 6 to 10 horsepower for each battery of 
three machines are used for the manufacture of sheet rubber, and 
motors of from 15 to 20 horsepower are used for similar batteries of 
rollers making crépe sheets. 
Electric driers, especially for crépe rubber, are being tried out in 
the Netherland East Indies, several being installed in 1929. The