His new phonograph reproducer was not exempted from this policy of attempted destruction, and before leaving for Europe he gave instructions for a grilling test, which was, of course, carried out faithfully, but the diamond point was found to be uninjured after playing records more than four thousand times. With such results he deemed it a safe proposition. On his return from Europe in October, 1911, Edison resumed his attack on the evolution of the new indestructible disc record with a smooth surface, the main principles of which had been determined upon before his departure. In addition, there arose the problem of manufacturing such records in great quantities. The difficulties that confronted him completely baffle description. The whole battle was carried on with the aid of powerful microscopes, which even at their best would fail to reveal the obscure cause of temporary discomfiture. Differences in material, dirt, dust, temperature, water, chemical action, thumb marks, breath marks, cloth and brush marks, and a host of major and minor incidentals, were patiently and painstakingly investigated with a thoroughness that is almost beyond belief to the layman. Day and night the work was carried on incessantly. During the height of the investigation, toward the close of this five-year campaign, Edison and a few of his faithful experimenters--facetiously called "The Insomnia Squad"--stayed steadily at the works for a period of over five weeks--eating, drinking, working, and sleeping (occasionally) there. During that time Edison went home only four or five times, and then merely to change his clothing. He and the men slept for short periods in the works or in the library, on benches and tables, resuming their labors immediately on waking up. Edison had arranged for an abundant supply of good substantial food which they themselves cooked, hence the inner man was well cared for. The wives of the men came around at intervals with changes of clothing for their husbands. This intense application to work left no time for shaving, with the result that all hands might well have been taken for a gang of traditional pirates from their unkempt appearance. They were all happy, however, and, strange to say, all increased in weight, although a contrary result might naturally have been expected. The intense work has never ceased, but there has been no similar protracted siege since, as the main principles were practically settled at that time. The foregoing instance has been merely mentioned to illustrate the fierce vigor with which Edison works when he is seeking to complete one of his inventions. He has been, and still is, prosecuting his labors with the same energy to bring about the utmost perfection that is possible.