Several kinds of lamps are used in carriages, both as regards principle of construction and form and ornament. In the simplest kind the light is furnished by the combustion of wax candles, which are contained in tin tubes, through a hole in the upper part of which the wick passes, the candle being pressed upwards as fast as it consumes by a spiral spring. In dress carriages, where the lamps are somewhat ornamental, wax candles are invariably used on account of their superior cleanliness, though the light is inferior to that of oil. Oil is often used on account of its superior illuminating power. The lamp then simply consists of a tin reservoir for holding the oil, and a round wick of the most ordinary kind, though sometimes flat for the sake of spreading the flame. Reflectors of many kinds are used in every variety of carriage lamps, formed of silvered metal highly burnished. Attempts have been made to bring the argand lamp, with a current of air through the wick, into use, but sufficient success has not attended these efforts to make them general, owing to their liability to be suddenly extinguished by violent draughts of wind. This may, however, be accomplished when the scientific principles of combustion and the regulation of the draught shall be better understood. By a common lamp is understood one that feeds the wick with oil by capillary attraction, the column of oil being below the level of the flame. An argand lamp, on the contrary, has a column of oil considerably above the level of the flame and constantly pressing upwards to it like a fountain. The motion of a carriage has a tendency to make oil at times flow too rapidly and extinguish the flame, and sometimes to cause too sudden a rush of air up the central tube, which blows away the flame from the wick; and when these difficulties are overcome by ingenuity they become such complicated pieces of work that it is beyond the ordinary “gumption” of the servants to trim them properly, and if this be not done the object of the improvements is defeated. The principle of constructing an argand lamp, so that it may regulate its own air draught, is set forth by Lord Cochrane in one of his patents. It is to divide the lamp into three chambers—one in the centre, which contains the reflectors and light, surrounded by the chimney glass, and is pierced with holes at the sides to permit the egress of the heated air and the ingress of the fresh air. From this chamber a tube or tubes communicate with the lower chamber, into which the air tube of the burner descends, and thus furnishes a regulated supply of air. It is evident by this process the air rushing in must be regulated by the air rushing out, and _vice versâ_.