Oil lamps of this period are collectively known as 'Argand' or 'Colza' lamps. Colza is the type of oil they burned, it was made from rape seed and was extremely thick and viscous. The name 'Argand' is a reference to the Swiss chemist Ami Argand (1759-1803). In 1783 he invented a burner which revolutionised the performance of oil lamps. Argand's burner consisted of two concentric tubes with a circular cotton wick between them, this enabled a double current of air to be drawn up through the wick. This produced a brilliance twelve times that of a single candle.