"But yet gas has gone up again lately. You may thank the electric-light boom for the temporary respite you have had from poor gas at high prices." "Yes; some of the companies put gas down lower than they could manufacture it, in order to hold their customers at a time when people almost believed that Edison's light would prove a success." "But it _was_ a success. It proved an excellent light, displayed a neat lamp, and gave no ill effects upon either the atmosphere or the eyes; and the perfect carbons showed a surprising endurance. The only difficulty is that the invention is not yet perfected so as to go immediately into use." "But the lower part of the glasses becomes dark with deposited carbon," returned the chemist. "If carbons could be made to last long enough to render the lamps cheap, this smoking of the globes would set a limit at which the lamps would cease to be presentable; and the cleaning, and the exhausting of air again, are difficult and expensive." "That remains to be proved. But coal is sure to grow dearer." "That isn't likely within a century. Besides, by the fault of the consumer gas-light costs now one-third more than it should for the same light. The best English authorities state this to be the case in Great Britain, and I have no question that such is the fact here." "How would you remedy the evil of waste?" "By the use of economical burners and of governors to regulate the flow of gas." "That is very easily said. What is the name of your economical burner?" "I am not an advocate of any special burner, but of all that are constructed on right principles." "There are many kinds of burners. Do you not have some classification for them?" inquired the young lady, who was fresh from Wellesley.