Difficulties are multiplied when we pause for a moment to think of Edison's influence on collateral branches of business. In the public mind he is credited with the invention of the incandescent electric light, the phonograph, and other widely known devices; but how few realize his actual influence on other trades that are not generally thought of in connection with these things. For instance, let us note what a prominent engine builder, the late Gardiner C. Sims, has said: "Watt, Corliss, and Porter brought forward steam-engines to a high state of proficiency, yet it remained for Mr. Edison to force better proportions, workmanship, designs, use of metals, regulation, the solving of the complex problems of high speed and endurance, and the successful development of the shaft governor. Mr. Edison is pre- eminent in the realm of engineering."

The phenomenal growth of the copper industry was due to a rapid and ever-increasing demand, owing to the exploitation of the telephone, electric light, electric motor, and electric railway industries. Without these there might never have been the romance of "Coppers" and the rise and fall of countless fortunes. And although one cannot estimate in definite figures the extent of Edison's influence in the enormous increase of copper production, it is to be remembered that his basic inventions constitute a most important factor in the demand for the metal. Besides, one must also give him the credit, as already noted, for having recognized the necessity for a pure quality of copper for electric conductors, and for his persistence in having compelled the manufacturers of that period to introduce new and additional methods of refinement so as to bring about that result, which is now a sine qua non.