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.