In other respects, however, its colour is objectionable, and Mr. Hewitt has experimented with a view to obtaining the red rays, thereby producing a pure white light. "Why not put a red globe around your lamp?" is a common 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 rays that are not red. Since there are no red rays 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, coloured with rhodimin, which, when thrown over the lamp, changes some of the orange rays into red, giving a better balanced illumination, although at some loss of brilliancy. Further experiments along this line are now in progress, investigations both with mercury vapour and with other gases. [Illustration: Testing a Hewitt Converter. _The row of incandescent lights is used, together with a voltmeter and an ammeter, to measure strength of current, resistance, and loss in converting._] Mr. 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. Further experimentation with the mercury arc led to the other two inventions, the converter and the interrupter. And first of the converter: _Hewitt's Electrical Converter._--The converter is simplicity itself. Here are two kinds of electrical currents--the alternating and the direct. Science has found it much cheaper and easier to produce and transmit the alternating current than the direct current. Unfortunately, however, only the direct currents are used for such practical purposes as driving an electric car or automobile, or running an elevator, or operating machine tools or the presses in a printing-office, and they are preferable for electric lighting. The power of Niagara Falls is changed into an alternating current which can be sent at high pressure (high voltage) over the wires for long distances, but before it can be used it must, for some purposes, be _converted_ into a direct current. The apparatus now in use is cumbersome, expensive, and wasteful.