THE TANTALUM LAMP. 



135 



a number of short pieces of wire were fixed on a support ino- fi-anie: 

 these pieces, connected in series, made up the total leni>th required. 

 Figure 3 represents a lamj^ thus constructed, the wire being fixed 

 obliquely in sixteen straight pieces between two insulated supporting 

 stars. Such lamps offer the advantage that short pieces of filament 

 can be used in the manufacture, but they are only reliable if the 

 wires used in the same lamp 

 are absolutely uniform in di- 

 ameter and quality. In the 

 end we arrived at the shape 

 represented in figure J^, which 

 is for 110 volts. 25 candle- 

 power, and 1 -5 Avatts ])er 

 Hefner candlepoAver. In this 

 form, differing from most of 

 the previous constructions, the 

 central support consists of a 

 short glass rod carrying two 

 disks, into wdiich the arms, 

 bent upward and downward 

 in the shape of an umbrella, 

 are cast. The u])per star has 

 eleven, the lower twelve arms, 

 each up[)er arm being in a ver- 

 tical plane midway between 

 the vertical planes in which 

 two adjacent lower arms lie. 

 Between these eleven a u d 

 twelve arms, which are bent 

 into hooks at their ends, the 

 entire length of the filament 

 is drawn in a zigzag fashion. 

 Its extremities, held by two of 

 the lower arms, are connecte;! 

 with the foot of the lamp by 

 means of platinum strips. 



The standard type for 110 

 volts 25 Hefner candlepower and 1 5 watts per candlepower has a 

 fdament 650 millimeters long and 05 millimeters in diameter. The 

 weight of this filament is 022 gram, so that about 45,000 lamps 

 contain together 1 kilogram of tantalum. The shape of the glass 

 globe is adapted to the frame described above. Care lias bi>en 

 taken to make it of a size not exceeding the usual maximum dimen- 

 sions of common incandescent lamps of the same candlepower 



Fig. 4.— Complete himp, full size. 



