148 TRANSACTIONS OF THE 
During the succeeding period the metallized carbon 
filament, the mercury arc rectifier, and the magnetito arc 
lamp were produced. 
Then came the development of the tungsten filament 
which has revolutionized electric lighting and made possible 
the X ray target and the tungsten make and break contact. 
The wonderful development of the electric furnace is 
a result of this laboratory. The perfection of this furnace 
has made possible the study of the magnetic properties of 
iron alloys, with the result that hysterices and eddy current 
losses have been greatly reduced. At present the research 
staff is over 150 and the laboratory is located in a modern 
seven story building and occupies a floor space of 66,500 
square feet. Power is supplied at 250 volts d.c. Three 
wire systems and at 40 cycles 3 phase 120 volts. In the 
laboratory power plant are sixteen machines which deliver 
power at different voltages and at frequencies ranging 
from 25 up to 2000 cycles. Currents up to 12,000 amperes 
and voltages up to 2,000,000 may be obtained. An elabor- 
ate switch board enables an operator to send any kind of 
current and voltage anywhere in the building. In the power 
house there are also a liquid air machine, an air compressor, 
two large vacuum pumps. 
The building is piped throughout with city water, river 
water, illuminating gas, compressed air vacuum, high pres- 
sure hydrogen, low pressure hydrogen, oxygen, high pres- 
sure steam. Distilled water may be delivered by gravity 
to any room, and 250 motors, 80 transformers and 60 
vacuum pumps are distributed through the building. 
On the first floor are offices, the library of 1400 vol- 
umes and the machine shops. The second floor is occupied 
by research work on insulation; by production work on 
Coolidge X Ray tube, and by the carpenter shop. Because 
of the importance of insulation, the company devotes much 
time to its improvement. On the third floor is the ana- 
lytical laboratory and electrolytic work. Also work on 
transformer steel and other alloys are on this floor. One 
can readily see the importance of a slight decrease in the 
