Nernst lamp

The Nernst lamp is not an incandescent bulb of the type we are familiar with, but rather it was developed from materials used for the production of gas lamp mantles. Walter Nernst discovered that the electrical resistance of some metal oxides drops at incandescence temperature and that they can therefore be heated with electric current. The lamp has a complicated construction: the housing is actually a small relay (a type of switch) that switches the lamp on after the pre-heating cycle and also serves to regulate the current flow through the iron-hydrogen lamp. After 1910 this lamp was only manufactured for special applications, such as lighting for microscopy.