Filament light bulbs

I found these clear glass filament bulbs in a tea shop with a retro feel. This is what the first sorts of light bulb looked light. The idea was to put a high enough current through a strip of conducting wire to make it glow without burning. The bulb contains an inert atmosphere so no oxygen can get in to react. If it did, the filament would burn away quite soon. Carbon was the first to be used - remember that graphite conducts. I have no idea whether these are carbon, platinum or tungsten, which was the most commonly used. Too much thermal energy was being produced by this type of bulb for each unit of light produced - but clearly not enough thermal energy to heat your room. It was wasted and so made the bulbs less efficient. This is why they have been replaced by the small fluorescent tubes.