Figure 40 is a drawing of a carbon filament lamp. The lamp comprises a glass bulb encasing a carbon filament. The glass bulb is held above a rectangular base by two supports. The bulb is shaped like a straight smooth gherkin. Each support has an electrical connection and is therefore made of a conducting material i.e. metal. The base, shaded differently, must be an insulator e.g. wood. The top support is high enough to hold the bulb above the base and the bottom support is flat underneath the bulb. A wire runs down from the top support, into the bulb and connects to the top of the carbonised filament. Another wire goes up from the bottom support, into the bulb and connects to the bottom of the filament.

 3.2 Lighting inventions