Higli Temperatures by the AfetJiod of Colour Identity. 

 Table III. 



I. 



Lamp. 



II. 



Watts 



III. 



Watt 

 loss. 



IY. 

 Effi- 

 ciency 



loss. 



Y. 



Lumens 

 Watts. 



VI. 



Temp. 

 ° Abs. 



mean horizontal 

 candles. 



Carbon 115 volts... 

 » >> 



Tungsten 115 volts,' 

 60 watts 



31 



18 

 1-25 



2 p.c. 



3 p.c. 



4 p.c. 



8 p.c. 



4 p.c. 



5 p.c. 

 7 p.c. 



16 p.c. 



34 5 



0-5 9 

 8-0 



0-9 x 



2,085 

 1,730 

 2,280 



1,745 



These losses are calculated for different efficiencies as a percentage of the 

 watts which would be required to maintain the filament throughout its whole 

 length at the temperature of its midpoint, assuming no loss by conduction. 



The difference between the temperature corresponding to 

 the colour of the light radiated from the centre of the filament 

 of any lamp of the above types, and that radiated from the 

 ivhole filament are given in Table II. The following results 

 are obtained by using the values in Tables II. and III. for 

 ascertaining what would be the behaviour of the filaments 

 used in this investigation had there been no cooling. 



Carbon Lamj>s. 



In ordinary lamps the watts and temperature are connected 

 by the relation 



logV^^ + i-oSlogK/r (12) 



Allowing for the watt loss as per column II., Table III., due 

 to conduction, the watt-temperature relation for a filament 

 kept at uniform temperature throughout its length and having 

 no conduction losses is : 



loguW^Ci-o-m+^eSfiiogxoT. . (ia> 



Likewise for ordinary lamps the relation between lumens 

 per watt and temperature is expressed by 



lo &o^ =C 2 -4-581og I0 T-1851og I0 (l+ ^. (14) 



Allowing in a similar manner for the efficiency losses 

 (column IV., Table III.), the lumens per watt and tempe- 

 rature relation for the ideal filament is given by 



log^.-C, + 0-199 -4-63, log T- 185 log(l+ ^). (15) 



