ntact of the atmosphere, and as the flame is also thinner its temperature is more uniform, and the vapor from the center of the wick is consumed equally with that from its exterior.
The combustion is also greatly aided by the draft caused by the glass chimney, continually bringing fresh supplies of oxygen in contact with the flame and protecting it from currents of air. The chimney was the invention of L'Ange.
Argand died in 1803.
A French mechanic named Carcel patented an improvement in 1800, in which the oil is pumped from the reservoir to the wick by power derived from a spring or by the ascending column of air above the chimney.
This is called the Mechanical Lamp, and is used in the large lamps for the Dioptric system in lighthouses.
The Argand burner as modified by Fresnel for the Dioptric system in lighthouses has four concentric wicks, the outer one 3 1/4 inches in diameter, and the great heat produced is carried off by two means, — overflowing the wicks with oil, and b