98 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



4000 candle-power, and is adapted to both direct and alternating cur- 

 rents. It is enclosed in a nickel-plated light-tight hood. 



Fig. 21. 



3. 90° Hand-fed Electric Arc Lamp* — This (fig. 22) is for exactly 

 the same purpose as the last. 



Fig. 2'1 



4. Acetylene Gas A]ypa/ratus.\ — This illuminant is considered inferior 

 to electricity. The arrangement of burners is shown in fig. 2;!, and the 

 generator in fig. 24. They are coupled by india-rubber tubing. 



Loc. cit., fig. 17. 



t Loc. cit., p. 19, figs. 18 and l!>. 



