THREE ELECTRICAL ACHIEVEMENTS 191 



Square, the red coming out more prominently by contrast 

 with the blue green of the light. 



'Tor many purposes," said Mr. Hewitt, 'Hhe light in its 

 present form is already easily adaptable. For shopwork, 

 draughting, reading and other work, where the eye is called 

 on for continued strain, the absence of red is an advantage, 

 for I have found light without the red much less tiring to the 

 eye. I use it in my own laboratories and my men prefer it 

 to ordinary daylight." 



In other respects, however, its color is objectionable, and 

 ]\Ir. Hewitt has experimented with a view to obtaining the 

 red rays, thereby producing a pure white light. 



''^Vhy not put a red globe around j^our lamp?" is a com- 

 mon question put to the inventor. This is an apparently 

 easy solution of the difficulty until one is reminded that red 

 glass does not change light waves, but simply suppresses all 

 the raj's that are not red. Since there are no red ra5"s in the 

 Hewitt lamp, the effect of the red globe would be to cut off 

 all the light. 



But Mr. Hewitt showed me a beautiful piece of pink silk, 

 colored with rhodimin, which, when thrown over the lamp, 

 changes some of the orange rays into red, giving a better bal- 

 anced illumination although at some loss of brilliancy. Further 

 experiments along this line are now in progress, investiga- 

 tions both with mercury vapor and with other gases. 



^Ir. Hewitt has found that the rays of his new lamp have 

 a peculiar and stimulating effect on plant growth. A series 

 of experiments in which seeds of various plants were sown 

 under exactly the same conditions, one set being exposed to 

 daylight and one to the mercury gaslight, showed that the 

 latter grew much more rapidly and luxuriantly. Without 

 doubt, also, these new rays will have value in the curing of 

 certain kinds of disease. 



The discoveries which resulted in the production of the 

 new lamp, were the stepping stones to the production of the 

 converter, both being applications of the study and develop- 

 ment of the mercury arc. Mr. Hewitt found that the mer- 

 cur>" bulb, when connected with wires carrying an alternating 

 current, had the curious and wonderful property of permitting 



