It is pointed out that "Previous inventions failed--necessities for commercial success and accomplishment by Edison. Edison's great effort--not to make a large light or a blinding light, but a small light having the mildness of gas." Curves are then called for of iron and copper investment--also energy line--curves of candle-power and electromotive force; curves on motors; graphic representation of the consumption of gas January to December; tables and formulae; representations graphically of what one dollar will buy in different kinds of light; "table, weight of copper required different distance, 100-ohm lamp, 16 candles"; table with curves showing increased economy by larger engine, higher power, etc. There is not much that is dilettante about all this. Note is made of an article in April, 1879, putting the total amount of gas investment in the whole world at that time at $1,500,000,000; which is now (1910) about the amount of the electric-lighting investment in the United States. Incidentally a note remarks: "So unpleasant is the effect of the products of gas that in the new Madison Square Theatre every gas jet is ventilated by special tubes to carry away the products of combustion." In short, there is no aspect of the new problem to which Edison failed to apply his acutest powers; and the speed with which the new system was worked out and introduced was simply due to his initial mastery of all the factors in the older art. Luther Stieringer, an expert gas engineer and inventor, whose services were early enlisted, once said that Edison knew more about gas than any other man he had ever met. The remark is an evidence of the kind of preparation Edison gave himself for his new task. CHAPTER XII MEMORIES OF MENLO PARK