"Well, I suppose the wonderful part is that it has strength enough to make a light," answered Harry.
"No, the remarkable thing is that the light which it emits is absolutely cool. Experiments which have been made go to show that there is no heat. In every form of light which man has been able to produce thus far artificially, a great heat is evolved, and it would be a most valuable discovery to find out why these insects are able to do it without raising the temperature."
"But what difference does it make if heat is produced?" asked Harry.
"The production of heat means the loss of power. The heat generated takes up more of the power than the light which is produced, so that it would be a great economy if the heat could be dispensed with."
"But if there was no heat in the light produced would it make any difference in the lamps themselves?"
"Unquestionably. The lamps would last much longer."
"What are the things which must be learned in order to get the secret of cold light?"
"Well, there are number of questions which must be determined. While it is known that the fire fly and the glow worm emit what is called a phosphores[p. 58]cent light, this fact is a mere prelude to the knowledge of what is the exact color of daylight."