LIVING FORMS AND LIGHT 539 



been suggested that " living lamps " made from these bacteria could 

 be used to advantage in coal mines and powder magazines, since as they 

 emit no appreciable heat, they would be absolutely without danger of 

 producing an explosion. They would certainly furnish a nice cool light 

 for use in summer; the author would very much like to have one here 

 in his little study now, in place of the Welsbach which is engaged in 

 turning some 98 per cent, of its expended energy into heat instead of 

 light, after a day that has shown 90° F. However, such lamps would 

 probably not do for anything like general illumination, even if the in- 

 tensity were great enough, for in their light any color effects beyond a 

 very limited range would he impossible. Color considerations would 

 not be a considerable factor in mines and mills, however, so this does 

 not interfere with this application. 



It is more reasonable, however, to consider that these luminous 

 forms mereby point to what is possible in the way of efficient light — to 

 serve as the goal to which all effort in the improvement of light-effi- 

 ciency must strive. This nmst be the ideal — light without heat. 



