We learn to restrain ourselves as we get older. We keep

In the mean time, during the progress of the investigations on the dynamo, word had gone out to the world that Edison expected to invent a generator of greater efficiency than any that existed at the time. Again he was assailed and ridiculed by the technical press, for had not the foremost electricians and physicists of Europe and America worked for years on the production of dynamos and arc lamps as they then existed? Even though this young man at Menlo Park had done some wonderful things for telegraphy and telephony; even if he had recorded and reproduced human speech, he had his limitations, and could not upset the settled dictum of science that the internal resistance must equal the external resistance.

Such was the trend of public opinion at the time, but "after Mr. Kruesi had finished the first practical dynamo, and after Mr. Upton had tested it thoroughly and verified his figures and results several times-- for he also was surprised--Edison was able to tell the world that he had made a generator giving an efficiency of 90 per cent." Ninety per cent. as against 40 per cent. was a mighty hit, and the world would not believe it. Criticism and argument were again at their height, while Upton, as Edison's duellist, was kept busy replying to private and public challenges of the fact.... "The tremendous progress of the world in the last quarter of a century, owing to the revolution caused by the all-conquering march of `Heavy Current Engineering,' is the outcome of Edison's work at Menlo Park that raised the efficiency of the dynamo from 40 per cent. to 90 per cent."

Mr. Upton sums it all up very precisely in his remarks upon this period: "What has now been made clear by accurate nomenclature was then very foggy in the text-books. Mr. Edison had completely grasped the effect of subdivision of circuits, and the influence of wires leading to such subdivisions, when it was most difficult to express what he knew in technical language. I remember distinctly when Mr. Edison gave me the problem of placing a motor in circuit in multiple arc with a fixed resistance; and I had to work out the problem entirely, as I could find no prior solution. There was nothing I could find bearing upon the counter electromotive force of the armature, and the effect of the resistance of the armature on the work given out by the armature. It was a wonderful experience to have problems given me out of the intuitions of a great mind, based on enormous experience in practical work, and applying to new lines of progress. One of the main impressions left upon me after knowing Mr. Edison for many years is the marvellous accuracy of his guesses. He will see the general nature of a result long before it can be reached by mathematical calculation. His greatness was always to be clearly seen when difficulties arose. They always made him cheerful, and started him thinking; and very soon would come a line of suggestions which would not end until the difficulty was met and overcome, or found insurmountable. I have often felt that Mr. Edison got himself purposely into trouble by premature publications and otherwise, so that he would have a full incentive to get himself out of the trouble."

This chapter may well end with a statement from Mr. Jehl, shrewd and observant, as a participator in all the early work of the development of the Edison lighting system: "Those who were gathered around him in the old Menlo Park laboratory enjoyed his confidence, and he theirs. Nor was this confidence ever abused. He was respected with a respect which only great men can obtain, and he never showed by any word or act that he was their employer in a sense that would hurt the feelings, as is often the case in the ordinary course of business life. He conversed, argued, and disputed with us all as if he were a colleague on the same footing. It was his winning ways and manners that attached us all so loyally to his side, and made us ever ready with a boundless devotion to execute any request or desire." Thus does a great magnet, run through a heap of sand and filings, exert its lines of force and attract irresistibly to itself the iron and steel particles that are its affinity, and having sifted them out, leaving the useless dust behind, hold them to itself with responsive tenacity.

A WORLD-HUNT FOR FILAMENT MATERIAL

IN writing about the old experimenting days at Menlo Park, Mr. F. R. Upton says: "Edison's day is twenty-four hours long, for he has always worked whenever there was anything to do, whether day or night, and carried a force of night workers, so that his experiments could go on continually. If he wanted material, he always made it a principle to have it at once, and never hesitated to use special messengers to get it. I remember in the early days of the electric light he wanted a mercury pump for exhausting the lamps. He sent me to Princeton to get it. I got back to Metuchen late in the day, and had to carry the pump over to the laboratory on my back that evening, set it up, and work all night and the next day getting results."

This characteristic principle of obtaining desired material in the quickest and most positive way manifested itself in the search that Edison instituted for the best kind of bamboo for lamp filaments, immediately after the discovery related in a preceding chapter. It is doubtful whether, in the annals of scientific research and experiment, there is anything quite analogous to the story of this search and the various expeditions that went out from the Edison laboratory in 1880 and subsequent years, to scour the earth for a material so apparently simple as a homogeneous strip of bamboo, or other similar fibre. Prolonged and exhaustive experiment, microscopic examination, and an intimate knowledge of the nature of wood and plant fibres, however, had led Edison to the conclusion that bamboo or similar fibrous filaments were more suitable than anything else then known for commercial incandescent lamps, and he wanted the most perfect for that purpose. Hence, the quickest way was to search the tropics until the proper material was found.

The first emissary chosen for this purpose was the late William H. Moore, of Rahway, New Jersey, who left New York in the summer of 1880, bound for China and Japan, these being the countries pre- eminently noted for the production of abundant species of bamboo. On arrival in the East he quickly left the cities behind and proceeded into the interior, extending his search far into the more remote country districts, collecting specimens on his way, and devoting much time to the study of the bamboo, and in roughly testing the relative value of its fibre in canes of one, two, three, four, and five year growths. Great bales of samples were sent to Edison, and after careful tests a certain variety and growth of Japanese bamboo was determined to be the most satisfactory material for filaments that had been found. Mr. Moore, who was continuing his searches in that country, was instructed to arrange for the cultivation and shipment of regular supplies of this particular species. Arrangements to this end were accordingly made with a Japanese farmer, who began to make immediate shipments, and who subsequently displayed so much ingenuity in fertilizing and cross- fertilizing that the homogeneity of the product was constantly improved. The use of this bamboo for Edison lamp filaments was continued for many years.