THE CONQUEST OF NATURE 



platinum, and Edison began at once experimenting 

 with this. He made a small spiral of very fine platinum 

 wire, which he enclosed in a glass globe about the size 

 of an ordinary baseball. The two ends of the wires 

 connected with outside conducting wires, which were 

 sealed into the base of the bulb. The air in the bulb 

 had to be exhausted and a vacuum maintained to 

 diminish the loss of heat and of electricity and to pre- 

 vent the oxidation of the platinum. But when the cur- 

 rent was passed through the spiral wire in this vacuum 

 a peculiar change took place in the platinum itself. 

 The gases retained in the pores of the metal at once 

 escaped, and the wire took on such peculiar physical 

 properties that it was supposed for a time by some 

 physicists that a new metal had been produced. The 

 metal acquired a very high degree of elasticity and be- 

 came susceptible of a high polish like silver, at the same 

 time becoming almost as hard as steel. It also ac- 

 quired a greater calorific capacity so that it could be 

 made much more luminous without fusing. To dimin- 

 ish the loss of heat the wire was coated with some metal- 

 lic oxide, and the slope of the spiral also aided in this 

 as each turn of the spiral radiated heat upon its neigh- 

 bor, thus utilizing a certain amount that would other- 

 wise have been lost. But despite all this, Edison found, 

 after tedious experimenting, that platinum did not fulfil 

 the requirements of a practical filament for his lamp; 

 it either melted or disintegrated in a short time and be- 

 came useless; and the other experimenters had met with 

 the same obstacles to its use, and were forced to the 

 same conclusion. 



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