220 
I may further observe that these prepared wicks burn 
more equally and last longer than others, and are also less 
disposed to charr. The cause of difference is apparent. 
If it be correct that oils purified with the sulphuric acid, 
retain a certain portion, notwithstanding the care to remove 
it, and if this acid seizes gradually on the wick and at last 
destroys it, when left for a considerable time in the oil,* 
certainly the preparation of wicks in a mode I have des¬ 
cribed, will be an infallible preventive against this dan¬ 
ger, since until the wick is lighted, the oil in which it is 
immersed, cannot penetrate it. 
I have now the honor to present to the class, fourteen 
lamps, all differing in construction, which were made in the 
course of my experiments. A detailed account of each 
would be tiresome. By examining them, the object which 
I had in view in their construction will be evident. One 
has a reverberatory machine, of white porcelain, made at 
Munich about twenty years ago. 
One object has particularly engaged my attention, that 
of ascertaining a mode by which the flame of the lamp may 
be regulated, without raising or depressing its wick. A 
tube about an inch long, in which the wick pipe is tightly 
inserted, and by which it is made to ascend or descend at 
pleasure, has answered my views. When the lamp is trim¬ 
med and prepared, the tube, which serves as a regulator, is 
made to descend until its upper extremity is on a level with 
the aperture of the wick pipe. The wick is then raised by 
a forceps and snuffed, taking care than rather more be left 
than is necessary for its burning with the most brilliant 
flame it can afford. The regulator is afterwards raised a 
little, and when the lamp is lighted, is adjusted to the 
height found necessary to afford the desired quantity of 
light. The higher it is raised, the smaller will be the 
flame, and vice versa. In order to extinguish the lamp, 
* This is asserted by many lamp makers in Paris. 
