ARGAND LAMP, a kind of lamp in which the wick, and consequently the flame also, is in the form of a hollow cylinder, through the interior of which a current of air is made to ascend, in order to afford a free supply of oxy gen to the interior as well as to the exterior of the flame; and thereby to ensure more perfect combustion and greater brilliancy of light than could be obtained either by the use of a single large wick, or by a series of small wicks arranged in a straight line. These objects are more perfectly attained by the addition of a glass chimney, which confines the air imme diately surrounding the flame, and produces an upward current which causes it to rise high above the wick. This arrangement was in vented about 1782, by Aime Argand, a native if Geneva. It is made in many different forms, one of which, with a chimney of copper instead of glass, is used in chemical operations For the emission of heat. The principle is also extensively applied to gas-burners. Mr. Hemmenway took out an American patent in 1841, for a means of avoiding the necessity of removing the oil chamber when an argand lamp is to be replenished with oil. The fountain or reservoir is to be supplied with oil through a short pipe at top, which is hermetically closed by a leather valve and ;crew cap ; and between the bottom of this .-eservoir and the pipe that conducts the oil to he burner, is an air chamber, which is sup :died with air by a tube passing up through :he oil reservoir. This air is made one of the neans of filling the vessel with oil.
Messrs. Bedington and Docker registered an improvement in 1849, whereby an argand amp is enabled to maintain a clear light for a ;Tenter number of hours than under ordinary ;ircumstances. The central air-tube, instead A' terminating, as in the usual argand lamps, nearly on a level with the top edge of the per orated air-cone, is carried about half an inch ligher, and has apertures made near its upper The outer case is also prolonged at top tc\ a similar extent, and is similarly perforated near the top. By this arrangement, currents
of stir are directed through the apertures into the wick, just below the point of inflamma tion; and thus the oil is prevented from beconing thickened or carbonized at that spot, which is so likely to occur in the ordinary form of argand.
Man! other improvements have from time to time been introduced in the argand lamp ; and out manufacturers in London and •r mingham, in the various Exhibitions of Manu factures which have taken place within the last few years, have shown how much external beauty as well as practical convenience may be imparted to these contrivances.
The name of Argand having become associ ated with the means of producing a bright light by a judicious arrangement of it haS been applied not only to lamps, but also to candles and furnaces. During more than forty years, attention has from time to time been directed to the possibility of producing Argand Candles—that is, candles constructed on the argand principle. As, in the argand lamp, air is supplied within the circle of the flame, so it has been thought that if air could ascend through the wick of a candle, the flame produced would be more brilliant. Many varieties have been tried, and some of them patented ; but none of them have yet become permanently and commercially successful.
The designation Argand Furnace has been lately given to an arrangement, in which a stream of air is made to mingle with the in flammable gases in the furnace, but is pre viously divided into a number of minute streamlets bypassing through small apertures. The principle has been known and partially acted on for a considerable time, but it was brought into is practical form a few years ago by Mr. Williams.
•