In the ordinary incandescent electric lamp, the brilliant light is produced by a glowing filament of carbon. The powerful current of electricity experiences so much resistance as it flows through this badly conducting substance, that it raises the temperature of the carbon wire so as to make it dazzlingly white-hot. Indeed the carbon is thus elevated to a temperature far in excess of that which could be obtained in any other way. The reason why carbon is employed in the electric lamp, in preference to any other substance, may be easily understood. Suppose we tried to employ an iron wire as the glowing filament within the well-known glass globe. Then when the current was turned on that iron would of course become red-hot and white-hot; but ere a sufficient temperature had been attained to produce the requisite illumination, the iron wire would have been fused into drops of liquid, the current would have been broken, and the lamp would have been destroyed. Nor would the attempt to make an incandescent lamp have proved much more successful had the filament been made of any other metal. The least fusible of metals is the costly element platinum, but even a wire of platinum, though it would stand much more heat than a wire of iron or of steel, would not have retained the solid form by the time it had been raised to the temperature necessary for an incandescent lamp. There is no known metal, and perhaps no substance whatever, which demands so high a temperature to fuse it as does the element carbon. A filament of carbon, and a filament of carbon alone, will remain unfused and unbroken when heated by the electric current to the dazzling brilliance necessary for effective illumination. This is the reason why this particular element is so indispensable for our incandescent electric lamps. Modern research has now taught us that, just as the electrician has to employ carbon as the immediate agent in producing the brightest of artificial lights down here, so the sun in heaven uses precisely the same element as the immediate agent in the production of its transcendent light and heat. Owing to the extraordinary fervor which prevails in the interior parts of the sun, all substances there present, no matter how difficult we may find their fusion, would have to submit to be melted, nay, even to be driven off into vapor. If submitted to the heat of this appalling solar furnace, an iron poker, for instance, would vanish into invisible vapor. In the presence of the intense heat of the inner parts of the sun, even carbon itself is unable to remain solid. It would seem that it must assume a gaseous form under such circumstances, just as the copper and the iron and all the other substances do which yield more readily than it to the fierce heat of their surroundings.