There were five important commercial instruments for measuring various electrical parameters developed around 1882 in response to interest in electric lighting: the voltmeter, ammeter, ohmmeter, wattmeter, and electric supply meter. Many of these small instruments are mounted in attractive hardwood cases with gauges and brass fittings. Geissler tubes, invented in 1850, evolved into colourful twisted glass conversation pieces, then into the microchip in 1959. Electric powered lighting remained impractical throughout most of the nineteenth century, but experiments with lighting lead to the arc-lamp of 1808, which used two carbon rods and then to the carbon filament lamp invented by Thomas Edison in 1879. Prior to electric lighting in the 1880s and a source to direct intense light, scientists used the heliostat, dating back to Willem Gravesande’s invention of 1742. Heliostats use mirrors attached to a rotating arm powered by a clock mechanism that follows the sun in order to keep the projection of light stationary for a variety of purposes.