In its fundamental idea the tungsten lamp is not very greatly different from the early Edison incandescent lamps, but in the application of the principle there is half a century of accomplishment packed into a little over a quarter of a century of years. Edison saw that he must have a filament that would carry the current of electricity, but yet one which would be of such high resistance that it would not take up all the current fed to it. He saw that he had to have a filament that would heat to incandescence with the electrical current, and yet one that would stand a certain amount of wear and tear, and which would not be consumed by the heat. To obtain the latter effect he put his filament in an air-tight glass globe from which the atmosphere was exhausted, leaving it in a vacuum. As there was no air, there was no oxygen, and hence there could be no oxidization, or, in other words, combustion of the filament. Edison thought that success lay in a carbon filament, and in these early days when he was experimenting at his Menlo Park laboratory he carbonized just about everything he could lay his hands on and tried heating the result to incandescence in the vacuum globe. Finally, on October 21, he carbonized a piece of cotton thread and put it in his vacuum globe in the form of a horseshoe loop. On connecting it with his electric circuit he was rewarded by seeing a brilliant incandescent light that lasted without dimming for forty straight hours. What a dim, dingy little light it was in comparison to the world famous lights that Edison now puts forth! And yet in one way it was the most brilliant light that ever had shone in the world, for it showed mankind the pathway toward a complete system of electric lighting by incandescent lamps. The carbonized cotton thread filament had many drawbacks, and Edison continued carbonizing various fabrics and fibres, including, it is said, some of the red hairs out of the beard of one of his loyal staff! At last he hit upon a filament made of carbonized Japanese bamboo that was very successful for a number of years, but this was later superseded by a cellulose mixture mechanically pressed out by dies. Meanwhile, several investigators began work with tungsten and a similar metal called tantalum because of their extremely high melting points, high resistance, and other technical characteristics favourable for an incandescent filament. For years they had no success because the metal was so very brittle that they could do nothing with it, but finally a filament of pressed tungsten was brought out. In this type of lamp several filament loops would be fused or welded together to make one complete filament. The result was a very fine light, but the little wire was too fragile to stand hard usage, and owing to the fact that the various connected loops were not all of exactly the same thickness, one frequently burned out far ahead of the others and caused early lamp failure.